is it the seals
Printed From: Kiwi Airgunners
Category: Technical
Forum Name: Pauly's Technical Area
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URL: www.kiwiairgunners.co.nz/forum_posts.asp?TID=658
Printed Date: 23 Nov 2024 at 1:43pm
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Topic: is it the seals
Posted By: kruzaroad
Subject: is it the seals
Date Posted: 12 Aug 2022 at 10:32am
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So the gamo does some wonderful groups then impact Point goes astray. I've got new seals on the way but have just chronographed it. Seems a bit of variation to me. What is the view of you more experienced technical ppl on this? All pellets were weighed and sized. high 694 low 650 Ave 668 shots all in 600fps last two didgets of numbers in order. 79,90,94,84,94,70,66,71,68,87,73,54,64, 58,50,68,59,68,55,60,64,65,56,57,62 Any thoughts appreciated. |
Replies:
Posted By: mercs
Date Posted: 12 Aug 2022 at 12:16pm
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That rifle seems to be problematic. When in doubt I push pellets home with back of ballpoint pen to ensure not being deformed when closing breach. i follow Crosman regime of 1 drop of silicon oil into chamber each 250 shots to keep seals healthy. Please note for the high power modern springers I only use Silicone Chamber Oil NOT Pelgun oil or ATF.  I have successfully used dovetail to Picatinny adaptor rail ($30 -$70)and fitted Stealth red dot ($80) or Stealth Reflex ($150) to my IGT's.  I have fitted several new scopes to my fusion and it works well for a few hundred shots. When it eventually wanders quick tightness check of action screws and target using sights to confirms all is well. Some of the Gamo IGT's seem to slam the piston into the end of the chamber more than others. I have never pulled one to pieces to investigate. I have been pleased with Gamo warranty response on the one occasion I requested a replacement so it may be worth asking the question. The only scopes up to the task of my IGT's have been Gamo 3-9x40 and NS 3-9x40 cheers
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Posted By: kruzaroad
Date Posted: 12 Aug 2022 at 1:54pm
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Cheers. The rifle has been very problematic. I voided the warranty ages ago when I removed the mag due to pellet deformation . So that is out. I check the pellets are seated in far enough every shot. When I removed the piston it wasn't that great looking, so I think the crossman oil every 250 shots is something I'll start doing after the seal replacement. Due to fact it will group for x amount of shots, I don't think it's the scope,as it will start regrouping again without adjusting the scope (deviation is way to much from aim point to be just my shooting and wind. I've looked at that. Blame shooter first and work back from that) and Ive lock tighted the screws they haven't moved. The info the red dot is awesome, Ive been toying with the idea, as I'm going to turn it into the scrub gun/short range (if I can stabalise it) and keep the tx as a longer range rabbit Gun. Im stoked to know that the red dot is used by another shooter and will now look further into that option. Eventual I'll replace it and muck around with my shock gel and carriage idea. So cheers appreciate the response. Any one else with ideas or options I'd still love to hear them. |
Posted By: Billbobnz
Date Posted: 12 Aug 2022 at 11:22pm
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You probably have checked the breech seal? I can't remember if on that model the seal is on the piston side or the barrel side? I've removed the mag on a Gamo before too, too many problems of jamming. Try what Merces says and push the pellet into the barrel, as he says if the pellet sits proud when you close the barrelt this will stuff the end of the pellet skirt and cause problems. Just make sure they are pushed in the same distance everytime and re shoot through the chrony and see if the fps spread tighten up If not wait till the new piston seal comes. |
Posted By: kruzaroad
Date Posted: 12 Aug 2022 at 11:54pm
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I'm pretty sure it's not deforming as I check it's sitting below the edge of the barrel, but I have a little pusher thing that I can seat it in further with so I'll try that tomorrow too double check. The seal is on the receiver side (model is roadster) guns going to get stripped,internals cleaned, polished,resealed,relubed put back together making sure it's all tight and working well. Sighted in at 10 then 26 meters on open sights, if still playing up after that cut losses won't waste any more time on it. Lots of ppl who's gamo work great for them, I may have just got a bad gun/model but hopefully just wants some tlc. |
Posted By: kruzaroad
Date Posted: 13 Aug 2022 at 11:41am
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Here's the last 2 digits of next string weighed and sized pellets, seated approx 3mm in barrel.Under the same shot as yesterday's mixed for comparison. (only 15 shots) mixed 79,90,94,84,94,70,66,71,68,87,73,54,64, weighed/sized 68,51,58,50,55,59,55,26,77,71,39,58,48, mixed 58,50,68,59,68,55,60,64,65,56,57,62 weighed/sized 41,67 Good drop in power over all, possibly bit more stable but some weird drops and spikes. Have to check for metal rubbing,and how much that piston can freeplay I think. Cheers Billbob that was well worth doing. Appreciated. |
Posted By: kruzaroad
Date Posted: 16 Aug 2022 at 2:25pm
So pulled the gamo open and had a good look. Not impressed. Done a bit of sanding to inside of stock as had rub points but at irregular intervals. It has ribs under it to hold bottom of receiver. All along one side and just front and rear on other side. Can't see that helping an even shock vibration pattern. But I may be wrong. Had a worn rubber on one side, where pin that holds trigger housing/piston housing to receiver.  Piston seal was embedded with a chunk of lead right at seal edge.(bottom of pic)  Seal Edge crap too  Sprayed with brake clean to see what came out, metal filings and brown crap I assume is protectent for metal when shipping. 
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Posted By: xyon
Date Posted: 16 Aug 2022 at 3:14pm
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An air arms seal should fit if you want to use a better seal or get one from https://www.customairseals.com/" rel="nofollow - - https://www.customairseals.com ------------- --- My favourites springer - Diana 52 PCP - FX Wildcat III |
Posted By: kruzaroad
Date Posted: 16 Aug 2022 at 4:09pm
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Have just got ahold of vaughans for new rubbers.Piston and barrel seal arivved yesterday. But will rember that for next time thanks. I'm currently looking at piston which has so much space between it and the gas plunger it's been rubbing on the gas housing during cocking.  Need to make spacer. (sujestions appreciated)  The gas ram end has play where it sits in the rear housing. Noticed that one of spring clips on trigger (previous pic) is broken. I have nothing against gamo but I'm starting to think I scored a rifle made from parts taken off other rifles that didn't make the grade. Sigh. |
Posted By: xyon
Date Posted: 16 Aug 2022 at 4:49pm
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Hmm, I would fabricate something on my lathe if it was mine. You might find something like an o-ring that is a tight enough fit to stay in place or beer can shim with tabs behind the ram? ------------- --- My favourites springer - Diana 52 PCP - FX Wildcat III |
Posted By: kruzaroad
Date Posted: 16 Aug 2022 at 5:06pm
| Just cut out an insert from milk bottle that stops the movement of the piston head so will get thin sheet metal for that tomorrow. The gas tube is thinner, but has that grove around it which would be ideal for a grommet so that's a good idea. Cheers. Aaah a lathe if only, milling machine for stock be handy too. sigh. Solid Bush mechanics for me. |
Posted By: Billbobnz
Date Posted: 16 Aug 2022 at 6:32pm
| The more you shim those spacings out the more consistent the gun will become, along with new seals. I'm not sure on your gun there but some you can swap the gas piston around so there it less weight firing forwards during the firing cycle thus reducing the recoil further making the gun more accurate (if you do do this you will need to have something in the piston head to keep the rod centralized) |
Posted By: kruzaroad
Date Posted: 16 Aug 2022 at 6:53pm
| I've just epoxyed the plastic from milk bottle to the piston ram head as it's such a good fit and doesn't move as it's always hard against the piston. The gap between the gas chamber and the piston is rediculous. Is about 3mm all the way round. I'm going to expoxy a shim on the gas chamber, piston arm end, to keep the piston level enough to go over the oring/grommet I'll put on, without it just chewing it up. It's Friggin crazy there's no way that gamo makes guns so far out of spec.Something is not right in my opinion. |
Posted By: mercs
Date Posted: 16 Aug 2022 at 8:08pm
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That galling is ridiculous the whole cylinder must be moving longitudinally. I googled "gamo igt overhaul" to find some examples and the disassembly I watched did not have any marks on the ram cylinder. The metal fines from the damage must be getting behind the seal and cutting it out. I expect the lead flakes are from storing the guns barrel up. Debris will end up dropping backwards, I would not think the lead would do much damage. Really interesting, appreciate the pictures, I would expect your supplier to provide some advice or support for such an unusual failure, that has nothing to do with the loading mechanism. Good Luck
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Posted By: kruzaroad
Date Posted: 16 Aug 2022 at 8:38pm
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gun is stored horizontal,usually vertical when closing the barrel,I think the bit of lead was from the mag when it was on, it damaged the pellets and didn't push them in very far. The scraping on the gas chamber was at the bottom the piston damage top (except bit of lead). That piston pic is after the brake clean and wiping it! Gun City who sold it know nothing , they recommended young's when asked if they could get seal in. Hunting and fishing tried to order seal but couldn't get one as gun City is sole supplier of that model. I voided the warrenty taking the mag Off. I'm dealing with vaughans now who are the gamo importer (have been since mag issue, which I decided to not take free replacement) . They sujested might be easier to get whole trigger/gas housing instead of back rubber, and got a quick rundown on what I have to do with it to get it running and I don't need the expense.So they know about it. Their OK he's looking to see if he has it tomorrow. But saving grace is I have tx, which has been a pleasure. Everything with that process was smooth from enquire to delivery to shooting. When I asked about a tuning kit he recommend not to put one in as they are constantly removing them and turning back to stock. Live and learn. If I had the machinary to make the parts I'd be in heaven and loving all the faults. For now number 8 wire. |
Posted By: kruzaroad
Date Posted: 16 Aug 2022 at 8:55pm
| I won't ditch gamo for their guns as ppl have good results with them, however as I have to assume this is how the gun is made and I can see major issues with it, I would not recommend the gamo swarm fusion 10x mag (Roadster version) to anybody. |
Posted By: kruzaroad
Date Posted: 17 Aug 2022 at 11:37am
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May have a found a big part of the issue going thru the schematic . Part number 16080 is totally missing. It's a spacer that stops the cocking arm from moving up when breaking the barrel.(checked out motion on gun this morning)  I'm now of the opinion that the end of cocking arm has been lifting into the gas cylinder body and sliding along it, pushing it up, causing the ram to lift the piston. This has corrected itself when barrel closed but caused undue pressure on piston seal, metal on metal rubbing inside of reciever  and probly uneven seating of the piston when cocked. Which would explain some of the peaks and drops in chrono readings as the tolerances would allow it to tilt. Wether it's broken or worn thru and fallen out, just dropped off as its a clip,out or was never there I have no idea but I've never seen it, or noticed it on my work bench. Emailed Vaughans for one this morning for new one. |
Posted By: Billbobnz
Date Posted: 17 Aug 2022 at 1:00pm
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You will be surprised how good this thing shoots once you've cleaned and polished everything and removed all unnecessary movemen. I'm ordering new piston and breech seal for my Hatsan today as since the rebuild it has become inconsistent. At 40m the goruping was a vertical gorup and after a few shot through the chrony was a high of 728fps and low of 680fps, breech seal doesn't seam to be producing a tight seal. Thanks to Mercs I have all my guns barrel up so I'm going to check for lead in the cylinder. My brother in-law brought a Gamo mach 1 in .177 a couple of years ago he is shooting stoger x hollow 10.43gr pellets through it and still shooting 3/4" groups at 40m |
Posted By: kruzaroad
Date Posted: 17 Aug 2022 at 1:43pm
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we will see. just in town now looking for 3000 grit sand paper. Can't find jb non embeding barrel cleaner anywhere. Of to repco see what valve grinding pastes they have. it's all fun. if it don't shoot well I'll turf the bloody thing. |
Posted By: kruzaroad
Date Posted: 17 Aug 2022 at 7:52pm
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Have to laugh at myself. Went into mitre10 with the receiver tube, poping bits of round dowl in it to find the best size. Got back cut a line down middle feed sand paper into it rolled it around started to polish air chamber. Suddenly dawned on me as I was putting the 2000 grit on, I could have brought honing tool or sand paper holder for the drill that would have taken 1/5 of time lol |
Posted By: Billbobnz
Date Posted: 17 Aug 2022 at 9:39pm
| I did something similar until I brought a Brake cylinder Honing tool from repco |
Posted By: kruzaroad
Date Posted: 18 Aug 2022 at 12:47pm
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That sounds perfect. I'm guessing your happy with the results. I've been looking into chrome polish for its abrasive qualities and it has two very soft/fine polishing compounds. I'm going to try a bit on the end of piston, clean it with solvent and see if it's smoother. If so I might do the barrel the same way. Lap it in. Probly do it after back together and tested. 
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Posted By: kruzaroad
Date Posted: 18 Aug 2022 at 5:34pm
| nope made no difference end of piston so will scrap that idea. |
Posted By: kruzaroad
Date Posted: 22 Aug 2022 at 5:50pm
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So gun back together. Everything polished, including trigger. Everything running smooth. (better than ever has) Trigger still way to much play before engages sear so might file that back a bit more or get a longer adjustment screw. New volicitys (about 30 shots in) Everthing in 700fps. Last 2 didgets every of shot. 12,05,10,16,19,15,12,13,12,15,09,17,15,14,05,07,05,00,17,17,15,16 HI:734 LOW:700 AVG:713 Re zeroed scope. Not happy with grouping. Trigger pull may be affecting my shooting. Pellet may be to lite for 700+fps Play more tomorrow. Pellets ftt 14.66gr. Had quick shot with aa16gr not much better.  Any ideas why spreading? Including shooting techniques. ( I pull much tighter groups with tx at 50m) Comments appreciated. |
Posted By: Pauly5
Date Posted: 22 Aug 2022 at 8:17pm
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Great thread. I haven't followed it completely, but can the red dot withstand the recoil? Have you tried it with open sights, or a solid scope to eliminate one more factor? Those speeds aren't bad, and at 25 m, I would find it difficult to shoot groups. Was there anyway to check the barrel crown? I believe this can effect accuracy quite a bit. Smack me if this has already been covered. |
Posted By: kruzaroad
Date Posted: 23 Aug 2022 at 8:44am
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I shot it to 15 meters with open sights and thought sweet and put scope on.(prob should have gone further) It currently has a gun City air rifle rated scope,in a one piece base, on gamo recoil damping base they come with.(red dot won't even look into till firing strait) I have no idea about the crown but will check it out on Web. That comment does make me wonder if its clipping the built in suppressor baffle. Will check that, probly remove internal baffle and see if tightens. I've seen no damage in bore but that's just looking through barrel with eye, so no noticeable damage might be better description. As for the groups if that's as good as it shoots at 25 meters, it's no good to me. I've already taken a hare with tx that had a pellet in rear leg from gamo prior to tx ( that would have been aimed as a heart shot on stationary hare) I've seen your videos and would find it hard to believe that you wouldn't be putting pellets through same hole at 25m Cheers you've given me couple more things to look at. It also came standard with a washer as spacer behind gas ram, wonder if removing that would help without dropping the power to much. hmmm |
Posted By: kruzaroad
Date Posted: 23 Aug 2022 at 9:30am
| just watched a couple videos and read a heap on crowns. So yep could be an issue going to check cat trap then have a look. Have a shrouded barrel that's going to sux for checking it. But good advice pauly5. |
Posted By: Pauly5
Date Posted: 23 Aug 2022 at 9:40am
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Ha ha, sorry, I really meant to say that I would find it hard to shoot good groups at 25 m with a red dot sight. slightly older eyes can struggle to focus on the close red dot and target at the same time. So if you had a scope with a fine reticule, you may find the groups tighten up, or at least you can eliminate that factor. You could try shooting into water and seeing if there are any bad looking marks from clipping? I have a 97k, and it shoots great, but when I first got it the stock screws would sometimes loosen, and this caused groups to open up, so make sure everything is tightened down positively and that the action sits comfortably in the stock. Another factor was tightening screws to the same torque each time. means the POI remained the same, but overtightening had the effect of putting a slight bend in the main tube, and effecting pellet speed from extra friction in the main tube.. I cheated in my videos, I was using a pcp.
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Posted By: kruzaroad
Date Posted: 23 Aug 2022 at 1:54pm
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Nothing cheating about pcp. Still uses pellets and follows the same laws of drop, wind, bc. Its my job to hold the gun right so it's a steady platform,and counter the recoil. Anyway went to other end of barrel to look at crown (which was fine) but the journey to it and past it a different story. 1: Pellet scuffing to the end cap on shroud.  2: Damage to baffle inside shroud.  3:Tooling Mark running radius of rifling and grooves. Having never looked through barrel from baffel end never noticed it before. It's taken about 50 odd photos to get these and they don't do justice to how clear, crisp and deep it is.    Targets shot at 25 without the baffle in to make sure it wasn't just baffle 
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Posted By: kruzaroad
Date Posted: 23 Aug 2022 at 2:09pm
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Ive sent the pics to gamo distributor and asked if this could be the issue with accuracy and will gamo replace the barrel. They also put a 5mm washer behind the gas ram (as standard) which I'm probly going to take out.It reeks of a gun that has just had a spacer put in to upgrade the power and I suspect that the piston is hitting the end of cylinder harder than it should, increasing recoil and doing the seal no good. I'd rather a lower power rifle (providing its not to big a drop) that hits where its aimed more than a faster rifle that puts pellets into the rear of animals your aiming to the front of. This gun has been a major pain in the arse, but worth its weight in gold as a learning curve that's for sure. |
Posted By: xyon
Date Posted: 23 Aug 2022 at 2:27pm
Hi, make sure the gas spring still has a few mm of preload after you remove the washer - otherwise it will kill itself as the internal parts slam together. BTW changing the pre-load on a gas spring won't change the spring force as much as a steel spring. ------------- --- My favourites springer - Diana 52 PCP - FX Wildcat III |
kruzaroad wrote:Posted By: kruzaroad
Date Posted: 23 Aug 2022 at 4:54pm
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Cheers Xyon. All ready dropped it and retested it by time read this.But have filed that info away for future. Guessing as still had to use gclamp to compress it to put pin in that holds it all in I fluked that one. whew. With washer out back in 600fps range. Last 2 digits 10 string group as follows 89,94,79,95,85,93,89,91,82,86. AVG = 690fps A lot less erratic and a lot less thump at end of stroke. 25m groups:with baffle and washer in 4.55cm,x 3.51cm baffle out / washer in 3.4cm x 3.7cm -Baffle out washer out 1st group 3cm x 3.4cm. 2nd group minus flyer ( really I pulled trigger to early coming onto bull) and a totally pulled it, leaves a 8 shot group at 2.3cm x 2.5cm  20m groups: (didn't shoot one earlier with baffle out) Washer in baffle in 4cm x 3.15cm washer and baffle out 2cm x 2.5cm  now if I can get that trigger adjustment screw in ten or prefablable 12mm length I'll be able to take out the rediculous amount of travel in the sear without filing it back any more. Get that machining mark sorted.clean up the baffle, I might have what gamo should have sold me. Cheers for advice. Any more fire away it's all been good so far. |
Posted By: Billbobnz
Date Posted: 23 Aug 2022 at 6:42pm
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Good evening, one thing to check is how much play is there in the breech? If you have a feeler gauge, remove the breech bolt that the barrel piviots on and feel for any gaps down beside the breech shim bushings. If there is even the slightest gap as the breech bolt is tightened it squeezes the front of the shim bushes and allows a MIT of lateral movement at the rear (hard to explain but you may know what I mean) a gazillion of a nanometer of movement here will throw your accuracy out. You will be able to get shim washers from a engineering firm near you to replace the factory ones to help remove any gaps in this area. Just another thing to check :) |
Posted By: Billbobnz
Date Posted: 23 Aug 2022 at 6:47pm
| I had this really crazy idea the otherday that I have no idea if it could be engineered. Is somehow fit a highflow regulator between the piston chamber and breech to regulate the pressure to allow more constant pressure behind the pellet for greater accuracy - almost had a brain aneurysm over the idea - if it's possible we all will patent it lol |
Posted By: Billbobnz
Date Posted: 23 Aug 2022 at 6:48pm
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Patent pending - Kiwiairgunners Hahaha |
Posted By: kruzaroad
Date Posted: 23 Aug 2022 at 6:51pm
| I had to read that about 4 times but yep I've got it. I'll do that in the morning and get what I need tomorrow in town. Excellent timing on your behalf. Great advice cheers. |
Posted By: Billbobnz
Date Posted: 23 Aug 2022 at 7:06pm
| I have a habit of explaining things in a way that usually ends up with a WTF expression from the listener....... |
Posted By: kruzaroad
Date Posted: 23 Aug 2022 at 7:12pm
It was all good. worked for mee 
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Posted By: kruzaroad
Date Posted: 23 Aug 2022 at 7:45pm
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chamber in front of end of piston stroke. one way valve to chamber (think flap of metal on inside, for example) air gets forced into chamber it seals from back pressure. that then goes to valve system above the chamber. Look like a pcp but be a single shot. A release button or forward trigger to release the piston. piston fires, high pressure chamber full. gun is loaded. firing separate to piston release. |
Posted By: kruzaroad
Date Posted: 23 Aug 2022 at 7:46pm
| oh under or side lever |
Posted By: kruzaroad
Date Posted: 24 Aug 2022 at 2:07pm
| So went to a place called fasttrade Group limited, a mate reckoned was good. it had the screw for trigger, shim washers, moly grease,fine valve grinding paste in general every thing I've had a prick of time finding. sweet. |
Posted By: kruzaroad
Date Posted: 24 Aug 2022 at 5:44pm
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Well all back together, shooting worse than ever. Dropped the scope off. got 4 shots before wind jumped up for evening. 1 shot pulled knew it as soon as pulled trigger ( which by the way is so much better with new screw. Still heavy but not a long drawn out (bit like this whole episode lol) pull to sear engages. Nice and crisp. 25m open sight, not sighted in since new, old eyes so compromise on focus of back sight and target Shame only got 4 shots in. But better than scope by long shot. So the saga goes on. Gamo scope back on tomorrow, if that sux remove the gamo shock suppression base. remount scope in another set of rings I have. Its pretty close to being a give it away rifle at the moment. 
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Posted By: Billbobnz
Date Posted: 24 Aug 2022 at 7:21pm
| Don't give it away, keep going and it could be that barrel after all. Let us know once the scope is back on how it's going |
Posted By: kruzaroad
Date Posted: 24 Aug 2022 at 8:39pm
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It's a a usable rifle now. I'll do more with open sight first. That last group was promising but to small to count. If it is the barrel then I'm over it. If gamo won't replace not paying for one. Could still use it for recoil experiment. (put that washer back in to give it kick) Or I could just send it to you billbob. You can use it for parts, find a barrel for it. I'm wasting a lot of time I could be strolling the farm with the other gun. See how tomorrow goes. Or the next day |
Posted By: kruzaroad
Date Posted: 25 Aug 2022 at 8:29am
| Right still no accuracy groups to wide to hunt with don't think I'll bother with it any more. Rather be hunting with tx than mucking around with a gun that has been problematic since day one. Will ring up about barrel today. But that's it. |
Posted By: Pauly5
Date Posted: 25 Aug 2022 at 9:57am
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Yea, I have wondered how well that would work too. Same principle as a single stroke pneumatic in the way it stores air pressure. You would only need the one stroke to store more energy than an SSP can with one stroke, but with more weight in the gun. I guess you would have to have the piston firing backwards so the plenum and valve is at the breech end too.
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Posted By: kruzaroad
Date Posted: 25 Aug 2022 at 10:50am
true. Don't have second trigger for piston release. Have lever system. Basic concept below.  I'm thinking thumb size push pad, Thin strong steel rod. Pressure is not an issue as its not a shot stroke. A spring for helping release pressre if too tight Feasable.??? |
Posted By: kruzaroad
Date Posted: 25 Aug 2022 at 11:07am
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I think to me the separate release of the piston is the only way to get rid of impact when shooting. I don't think that designing the release mechanism is outside the realm of ppl here. I don't think the initial piston firing is an issue for shooting as it can be done on way to shoulder after cocking. I don't see the mechanism adding to much height or weight. Or overly complicated. Would it be rated as a pcp as it has a precharged chamber? |
Posted By: kruzaroad
Date Posted: 25 Aug 2022 at 12:26pm
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That's cool, gamo dude is going to see if they have any barrels ( they don't bring over spares) I've said any barrel that fits and is in good condition is fine. Doesn't have to have the suppressor fluting plastic surround. Here's hoping |
Posted By: kruzaroad
Date Posted: 26 Aug 2022 at 2:27am
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Or flip the piston release mechanism upside down, extend the connecting rod, turn release lever into second trigger. Side lever to reduce bulk underneath.  Cocking lever should be release lever sorry. |
Posted By: kruzaroad
Date Posted: 26 Aug 2022 at 2:44am
| Theory would have it that if your piston has enough force to load the pressure chamber through the port, it's probly going to be strong enough to seal the chamber and no none return valve needed. |
Posted By: xyon
Date Posted: 26 Aug 2022 at 6:28am
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Don't want kill your creativity 😜 But there are a couple of reasons why the valved springer would not work well. If you store the air at the end of the piston stroke. Then you do have a single stroke pneumatic, which we all know is quite a bit less powerful than a spring rifle. Why is that? Can you guys tell me 😁 The pellets in a spring rifle acts as a kind of valve. The pellet holds in the breech until the pressure is high enough to force it into the barrel. The volume of the transfer port on a springer must be as small as possible for high efficiency. If you go adding valves and crap between the piston and the pellet, the efficiency and power will suffer. ------------- --- My favourites springer - Diana 52 PCP - FX Wildcat III |
Posted By: kruzaroad
Date Posted: 26 Aug 2022 at 9:19am
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I thought that's what we were talking about. A single shot. I be keen to know why a high pressure chamber storing the equivalent amount of air as the piston chamber ( more actually as there's the air in the chamber before compression) would produce less power than a piston alone. But I guess pump action take more than I stroke. Still larger piston chamber to smaller the pressure chamber higher the pressure. Don't worry about stifling my creativity, I'm just throwing ideas out. Just a mind exercise. I'll look further into air compression facts see what I'm dealing with.
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Posted By: kruzaroad
Date Posted: 26 Aug 2022 at 11:46am
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From what I've managed to piece together from the Web the compressing air to chamber is sweet, it's a simple formula. I'll do some calculations later probly from hw97@45cc and Diana 350@70.8cc. The real energy sapper seams to be the heat produced between the piston and reciever and the port. They reach really high heats, 700+ this expands the air, converts energy to heat, (tighter the port more the heat) when that cools in the chamber, its of a lesser volume. Actual lose still to be found out. I'll post a link to a boyles law calculator for anyone interested http://www.endmemo.com/chem/boyle.php |
Posted By: xyon
Date Posted: 26 Aug 2022 at 1:58pm
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You're right, the springer makes the air very hot, but it does not have much time to transfer the heat anywhere, so the pressure peak acting on the pellet is very high, but as the pellet moves down the barrel the air expands and cools again. For a single stroke pneumatic, the heat is lost, that means part of your pumping energy is lost. So when you pull the trigger on a SSP the air is expanding and getting cold and decreasing in pressure more quickly. ------------- --- My favourites springer - Diana 52 PCP - FX Wildcat III |
Posted By: kruzaroad
Date Posted: 26 Aug 2022 at 4:26pm
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Any idea of the equation or a site I can use, to find out what the temps get too? Knowing that I could work out the decress in air. I have a simple design in my head to keep heat to a minimum entering the pressure chamber. At 45cc the the air compressed to a third made 2bar approx.( no loss from friction or cooling in that) If I can alculate the loss I can adjust the storage volume for when cooled. Oh a barrel has been sent to me today free of charge. Off a returned gun with mag problems. sweeeeet |
Posted By: mercs
Date Posted: 26 Aug 2022 at 5:47pm
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Good luck with the barrel, and sensible option from Gamo supplier, I am pleased they followed through. Look forward to a much improved rifle. My fusion is a scope buster so I was interested in what you found with the spacer washer. Mine is a .177 and actually shoots quite well using fixed sights. Agree I would rather lose energy to gain accuracy and scope longevity. cheers
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Posted By: kruzaroad
Date Posted: 26 Aug 2022 at 6:01pm
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I'm more than happy with the spacer washer out. It's 5mm and it added thump to the forward stroke. It was a noticeable difference. I had to use a gclamp and washers to recompress it. So there is pressure there from the start. I actually hate to think how much harder it was hitting. I was just reading an artical I stumbled on looking for friction info, about the affect of a harder springs (and gas rams in particular) having more effect on recoil when the initial jolt of the ram releasing, the than the end of stroke. |
Posted By: Billbobnz
Date Posted: 26 Aug 2022 at 9:12pm
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Pauly5, you have actually brought up another idea I've had.... I've also thought for a long time at having the piston firing backwards a bit like a rifle sized version of a Webley pistol but having a fixed barrel and side lever would be easy to make a bullpup version and still have a full length barrel. |
Posted By: Billbobnz
Date Posted: 26 Aug 2022 at 9:20pm
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Xyon, yes you are right it would have a big impact on power output. But I would rather a slower accurate pellet (say 550-600fps in .22) over a faster inaccurate shot. The thing that wouldn't work is having a regulator that would allow the high flow during the shot cycle, Nothimg would be worse than having a delay in the shot cycle Does anyone know the pressure that the piston builds up in a brake barrel? |
Posted By: kruzaroad
Date Posted: 27 Aug 2022 at 7:40am
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that's a variable question. are you after the pressure that spring will impart to pellet which so far I've found to be ( in limit research so far) 30% of the spring energy. The actual pressure if there was no air port which probly need a formula, or the pressure of the cylinder that is needed to start the pellet which from memory is about 1200 (don't quote me on that) rechecked Here's the info from download below The pressure in the chamber does not begin to build up significantly until the piston is about 1/2 inch from the end of the chamber. At this point, the pressure goes up dramatically from around 120psi to 1200 psi at 1/10th inch from the end when the piston stops. This dramatic increase is only because the pellet is totally blocking the escape of any air. At around 1200psi, the pellet releases it's grip and accelerates up the barrel. Without the pellet, there will not even be close to enough pressure to stop the piston so the piston will slam into the end of the chamber. Which leads me to the question, if your precharging a chamber will it hold the piston back, and if so when firing will the piston then travel the rest of the way creating shock/recoil. If so will it be less? |
Posted By: kruzaroad
Date Posted: 27 Aug 2022 at 7:47am
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https://www.mediafire.com/?5mcemcyutrm Pdf of book "Trigger to muzzle" comprehensive study of internal workings of springer air guns. More formulas for working out stuff that you can shake a stick at. Older study by 3 independent guys. Equations all relevant to modern springers guns if you have the input data. |
Posted By: Pauly5
Date Posted: 27 Aug 2022 at 8:45am
| You would need a non return valve between piston chamber and plenum to store the pressurized air, or else the benefit of the "swept volume" with piston momentum is lost, and then you've really only got a single stroke Pneumatic |
Posted By: kruzaroad
Date Posted: 27 Aug 2022 at 10:34am
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One shot is all you will get out of a standard size springer set up. It's all I'm looking at. The increase in volume for doing multiple shots I have no dought would be to large and heavy. The addition of a larger storage chamber for high pressure would facilitate the ability for more than one shot but need multiple pumps. Im working on the principle of springer convenience of one pump, no outside precharging and getting rid of the recoil while shooting. If you want to increase the air chamber size for more than one shot your going to need custom seals, custom piston, custom receiver. I'm trying for the idea adapting a cheap air rifle for experimentation for proof of concept. What diameter air chamber do you think is the largest you can go without getting to big and I'll look at the volumes and pressure, see how much air a single pump will store under pressure and volume, the increase of friction over seal diameter, increase of heat through port to high pressure chamber, increased piston weight (though design could drop that) extra force needed to cock the barrel, etc etc, but I dought it will be more than two or three at max. Thats if you don't want to do that yourself. You will never get the volume storage of a pcp ( which is highly compressed from machinary using multiple compression strokes) in a single stroke action (in my view) but you can get enough for high pressure storage for a single shot from what I've looked at so far and even that may require a larger cylinder diameter or longer piston stroke to over come the loss of energy compressing into chamber. Havent worked all that out yet. Anyone who wants to and post results please do. |
Posted By: kruzaroad
Date Posted: 30 Aug 2022 at 9:31am
Happy days. Barrel just arrived. Wish he had left the cocking arms on as they are pressed over on ends. Still barrel rifling looks clean and crisp and most importantly there is no dirty great gouge around the rifling. You can guess what I'm upto now. Hopefully be posting a few targets that are tighter in groups later today.
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Posted By: Billbobnz
Date Posted: 30 Aug 2022 at 10:33am
| Awesome, let us know how it shoots |
Posted By: kruzaroad
Date Posted: 30 Aug 2022 at 4:22pm
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So barrel on, had to change rear sight blade as the fiber optic wire was broken on replacent. Haven't tested all of my pellets yet. Grouping much better 20m some nice tight performance from gun City Javelin. ftt held inside an inch but bit spread in that inch. AA field showed some promise. 25m changed the story. AA field to spread out. hornet shows promise. ftt bordering the edge of inch. Javelin OK will look at that again. white field had so many damaged pellets and such a thin skirt I didn't shoot them and won't buy them again. GAMO Pro magnum preformed awful and three pellets of the ten I selected wouldn't fit in barrel ( I guess with a hammer they would have) But the one that beat them all at 25m was stoeger x-field. An under dog that didn't preform in old barrel at all. The gun seems to like 14.66gr. ftt was the best performer with old barrel and is same gr. Did OK this time too. I'll run through the rest of tins tomorrow but for now I'm happy gun shoots at last  
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Posted By: Billbobnz
Date Posted: 30 Aug 2022 at 6:43pm
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That's an improvement. The guncity javelins and stoeger are made by H&N and I've had good success with them before. I've just replaced the breech seal with the new seal from custom air seals on my Hatsan .25cal and put two pellets into a tin can at 43yards first pop, will do the piston seal once I've got time but so far so good. Nothing worse than having a gun that your not sure if your going to hit something, and particularly with an animal that you could wound it |
Posted By: kruzaroad
Date Posted: 30 Aug 2022 at 7:59pm
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true that. I imagine at 43 yards the .25 would have a good whack to it. I must try a larger cal one day. keep us informed of its progress |
Posted By: mercs
Date Posted: 30 Aug 2022 at 8:17pm
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Nice result with the barrel change and the X-Field pellets. A frustrating journey but rifle now looks to be a genuine hunter with those groupings. I use the H&N Barracuda Match or H&N Hunter Extreme and H&N FTT are a reliable go-to. Interested how the Air Arms test as they are a well respected option. Never tried the Hornets so keen to see how they stack up. Full marks for perseverance and taking the time to share on the forum.
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Posted By: kruzaroad
Date Posted: 30 Aug 2022 at 8:25pm
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the air arms I thought were going to be the go to first 5 rounds at 20m punched one hole about three pellet diameter. The pellets are good quality and I was shooting the under weight ones I had sorted out. so would have been bonus if they did. But they spread at 25. There is a definite weight thing with this gun or maybe I shoot better with the 14.66gr. I'll shoot up shed and get the air arms targets out of bin and post them for you. |
Posted By: kruzaroad
Date Posted: 30 Aug 2022 at 8:50pm
 
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Posted By: kruzaroad
Date Posted: 30 Aug 2022 at 8:52pm
| wasn't sure what I'd shot at centers and not sure what one was AA field at 25m so didn't do those targets. there's about 20 from today. |
Posted By: Billbobnz
Date Posted: 30 Aug 2022 at 8:55pm
| Just going to say that they are very good groupings for open sights. I took a scope off a Ruger Air hawke a few weeks ago and used the open sights and they are an almost forgotten skill. My first couple of air rifles only had open sights and I could pop off Sparrows out to 30 odd meters using old Winchester pelets and when I first got a scope it took a while to get to get used to it. (Mind you it was a sh*tty second hand job) |
Posted By: kruzaroad
Date Posted: 30 Aug 2022 at 9:02pm
| sorry to disappoint that was scope after tried open sight and seen it was grouping. no adjustment to scope just shooting for groups to see what to use. Not particularly fussy about being dead center as just finding what I'll retest. Hence why stoeger shocked me with its 25m groups. I never shot them under 25m! |
Posted By: Billbobnz
Date Posted: 30 Aug 2022 at 9:14pm
| Haha sorry I obviously didn't read properly. I've got a tin of the stoeger in .177 that hasn't been touched. My brother in-law says his Gamo loves them. I need to try them |
Posted By: kruzaroad
Date Posted: 30 Aug 2022 at 9:29pm
| They seem to be well made. I never sorted any. They're strait from the tin, skirt checked for damage before loading. None were damaged, all looked well formed and even in shape all over. Pretty clean. That's a discription of pellets in tin, not just ones shot. |
Posted By: kruzaroad
Date Posted: 31 Aug 2022 at 6:18pm
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omg was shooting next tins of pellets checking grouping, suddenly the pellets dropped and started wondering. rezeroed scope nah. Gun City scope dead. Gamo scope back on and shooting again. This is unreal, like that movie christen the haunted car. Not hard to see why some ppl don't like air guns. What a learning curve this has been. Thankfully the tx has balanced it out with no issues and good shooting. lesson learned. |
Posted By: kruzaroad
Date Posted: 31 Aug 2022 at 6:19pm
| Still be able to use gun City scope as hand held range finder offa the mildots so not all is lost. |
Posted By: Billbobnz
Date Posted: 31 Aug 2022 at 6:31pm
| Been there before with scopes. I've got a cheap $60 scope that has been on several rifles and still hold zero and other scopes crap out in a couple of weeks. I lent a rifle to a friend once and he said he could hit anything so I got it back and the inner tube thing was rattling around free |
Posted By: kruzaroad
Date Posted: 31 Aug 2022 at 6:47pm
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Long as airmax holds. I'll look back into redot scope for gamo I think. Should do for short range. I'm blaming that washer when it was in. Also being stupid enough to listen to a sales person instead of saying no. All up I could have got another tx200 for the money I've spent on gun, scope, gas getting stuff and time repairing it. My fault I went for the fancy mag to try it instead of bsa single shot for same price. lesson learned. (Hopefully) |
Posted By: dvlnme
Date Posted: 01 Sep 2022 at 7:55am
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unfortunatly sometimes learning curves can be expensive eh!we all been caught out here and there the lesson is to not get caught out again i guess,bloody shame tho this happened to you but i learnt lesson from what happened to you as was considering the same rifle but wont be now, cheers mike
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Posted By: kruzaroad
Date Posted: 01 Sep 2022 at 9:33am
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Good move on your behalf. Just out of interest I stumbled on a review from aar that was a review of the roadster and speedster. Not a word was said on the roadster nor any shots fired from it. Think it goes to the old addage of you got nothing nice to say. I repeat that I got a bad gun. I don't recommend roadster as a gun but I still think I got a bad roadster. I'm not ditching gamo as ppl seem to have good results with them but I'm not Impressed. Basicly a pre assembled kit set that needs finishing. I might have saved a lot of hassle if I had stripped it from day one. If I ever get another gamo I will definitely strip it clean it up, check tolerances before I ever shoot it. |
Posted By: mercs
Date Posted: 01 Sep 2022 at 9:13pm
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Just moved the Stealth Reflex to my Gamo Fusion rifle and working well this afternoon, ready to go out for some pest control with the spotlight. Dovetail to Picatinny rail adaptor is required for this setup.  |
Posted By: kruzaroad
Date Posted: 01 Sep 2022 at 10:03pm
| That looks good. I think I'll have to follow suit. How far you shooting upto? |