Crosman hollow probe build
Printed From: Kiwi Airgunners
Category: Technical
Forum Name: Pauly's Technical Area
Forum Description: Technical information, Modifications and DIY projects are all in here
URL: www.kiwiairgunners.co.nz/forum_posts.asp?TID=806
Printed Date: 23 Nov 2024 at 10:08am
Software Version: Web Wiz Forums 10.14 - http://www.webwizforums.com
Topic: Crosman hollow probe build
Posted By: Pauly5
Subject: Crosman hollow probe build
Date Posted: 09 May 2023 at 10:11pm
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With new enthusiasm I started making a couple of new hollow probes. These allow the air or CO2 to travel up and act directly into the back of the pellet. The other design factors i've included are a tapered edge that fits inside the pellet skirt and enough length that it seats the pellet past the transfer port into the breech. I tapered the edge so that it should help engage the skirt with the rifling and so create a good seal. I will let the photos do the talking, but this is progress so far. First photo shows the main profile and O ring groove formed  Here you can see the probe halfway across the TP, and second photo shows a clear passage through probe.   The next couple are various angles of the hollowed out probe. I still need to workout the bolt hole angle and placement so that the hole lines up with the transfer port when pushed home.   One more showing how the taper fits into the pellet skirt.  |
Replies:
Posted By: Billbobnz
Date Posted: 10 May 2023 at 9:04am
| wow great work Paul, let use know if you get any increase of power when you test shooting it |
Posted By: nunga
Date Posted: 10 May 2023 at 10:57am
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I would be interested to see how much it cools down per shot due to the CO2 expanding at a faster rate. Looks good! ------------- 2nd place HP springer - WFTF World Championships 2014 |
Posted By: kruzaroad
Date Posted: 10 May 2023 at 11:07am
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Would not the easiest way to line the hole be to make the bolt/probe minus the hole, then with the breach attached to the barrel, lock the bolt shut turn the breach and barrel upside down in a vice, aline it and with a drill press, drill it to just shy of actual circumference needed then finish it off out of breech. This to me would eliminate the need to have to work out angles, as the hole is drilled at the correct point for the locked position of the bolt. I love the tapered edge for end of probe. Assuming that pellet skirts are even and not causing a lockup against the barrel, I imagine that air/CO2 will after the initial push starting the pellet, push back causing the skirt to flare nicely with good pressure. Be keen to hear results when done. Looks like I might be ditching the extended probes I have which are awsome for your design if they work well. And of course if I can persuade you to make me a couple. |
Posted By: Pauly5
Date Posted: 10 May 2023 at 12:32pm
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I haven't tried it on CO2 yet. Kruza, I had made one a while ago, and so I have exact measurements to follow that work for the probe tip, but I have made a hardened centre punch tool for marking the exact position of the bolt hole while the probe is in position. So this definitely works, but haven't compared it with the extended probe, but I feel both benefit over the factory probe by getting the pellet past the transfer port and have less restriction for the air/CO2 to get behind the pellet. I am going to try and make a few while I have my "flow on" if you know what I mean.  Billbobnz, I reckon there is an increase, but I often forget to make notes before I start, so don't have the comparison. I have fitted one to my 362, and compared it to a brand new 362 out of the box, and from 8 pumps I am getting 13.8 fpe, and the new std gun got 12.2 fpe with the same pellets.
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Posted By: J-S
Date Posted: 10 May 2023 at 2:07pm
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Looks awesome! Could you have done the bolt handle first, close bolt firm in the breech then marked the TP hole for location? ------------- https://www.instagram.com/js_airguns/" rel="nofollow - J S Airguns Air Arms TX200('s) Theoben Sirocco HW77 FWB 300s Webley Patriot One or two others... Current projects: Too many.. |
Posted By: Pauly5
Date Posted: 10 May 2023 at 6:53pm
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Yep, ok JS and Kruz I agree that would work too. I don't drill the hole in the probe tip, but run a small round file across it. I didn't drill it because the wall is quite thin, and I was concerned if the drill bit snagged it would pull it out of shape and bugger it up. But I could definitely mark it up that way and then form the hole.
I'll do it on the next one. |
Posted By: kruzaroad
Date Posted: 10 May 2023 at 6:55pm
But if it doesn't work you welcome to give us grief for the sujestion 
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Posted By: jwabfrog
Date Posted: 11 May 2023 at 8:36am
| Awesome engineering Pauly, you obviously have a lathe? Jeweller's size or something bigger? |
Posted By: Pauly5
Date Posted: 11 May 2023 at 9:07am
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Yea, it's a small one from the toolshed. Often referred to as a Chinese mini lathe. I've had it a couple of years now and it's addictive learning how to set it up and use it. I'd recommend it if you're looking for another hobby. One thing I have learnt to appreciate is that tolerances are so important, and you can often make an ordinary everyday item better by reducing tolerances.
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Posted By: kruzaroad
Date Posted: 11 May 2023 at 9:32am
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He put a pic of his lathe up on the site here http://www.kiwiairgunners.co.nz/forum_posts.asp?TID=721 |
Posted By: Pauly5
Date Posted: 11 May 2023 at 10:52am
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I finished drilling and fitting a bolt to the probe last night. The bolt is one I had started ages ago, and is probably too big to most peoples liking, but the good thing is that they are interchangable, so as I develop a good method of making the bolts, I will replace it later. Probe fits and slides well in the breech, but the pellet can catch on that annoying screw hole in the bottom, so I am thinking of turning up small delrin plugs to fit in there, and see if that works. Anyway here's a couple more photos.    |
Posted By: kruzaroad
Date Posted: 11 May 2023 at 11:14am
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That looks good. I prefure a larger bolt handle personally, makes for easier working of bolt when your watching that starling moving around in the tree. Then you only have to take eyes off it to put pellet in. Those little plugs are a good idea to block that screw hole. Are you going to reem/polish the inside of the hollow probe to smooth air flow through it? It may just be the photos make them look worse than they are but it looked pretty rough on the inside. |
Posted By: Pauly5
Date Posted: 11 May 2023 at 11:31am
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I drilled it, then followed through with an end mill bit to flatten the bottom of the hole. I will probably try sandpaper on a dowel, but it's the light that makes it look worse than what it is. I don't have any reaming tools.
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Posted By: kruzaroad
Date Posted: 11 May 2023 at 11:36am
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I found also that when taking close ups up it tends to make every little channel or groove look like a valley. Hence why I was a dubious about if it was just photo or actual finish. |
Posted By: Billbobnz
Date Posted: 11 May 2023 at 8:50pm
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Mate they are making me want to get a lathe..... Hopefully getting one at work soon. So hopefully will finish a few projects around here. |
Posted By: RangerPete
Date Posted: 11 May 2023 at 9:37pm
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Hi Paul, I don’t know much about pellets and probes, but would the beveled edge of the probe help in “reshaping” a damaged skirt as it seats it into the barrel? I’ve often wondered if shaping a pellet probe exactly as you have done would be able to gently “re-round” a bent skirt helping it to seal better, be more accurate etc etc… ------------- Walk quietly, but carry a big stick. |
Posted By: kruzaroad
Date Posted: 11 May 2023 at 9:55pm
Fear not billbob you can always use a drill and a file.  You'll have ball if you get one at work,and you got the old fella up the road to give you some seriously good tips and tricks. |
Posted By: Pauly5
Date Posted: 11 May 2023 at 10:42pm
| Pete, that was the thinking behind that, in the hope it would help do that and seat the pellet skirt onto the rifling. |
Posted By: Pauly5
Date Posted: 11 May 2023 at 10:44pm
That is exciting.
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Billbobnz wrote:Posted By: RangerPete
Date Posted: 13 May 2023 at 2:27pm
👍🏻👍🏻👍🏻 would be interesting to do some simple tests and see if it works, once you have a working prototype 👍🏻 ------------- Walk quietly, but carry a big stick. |
Posted By: Pauly5
Date Posted: 13 May 2023 at 8:51pm
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It's been a good day in the workshop. Today I took the 362 apart to work on the valve area, Drilled out TP in the barrel to 4 mm drilled out TP to 4 mm shaped the outlet valve in the valve body I started to slim the valve stem and broke it, so I ended up making a new one. I didn't thin out this stem, but round off the edges of the valve stem body for better flow around it, but only minimal difference. I also made a delrin spring seat which would increase the hammer spring tension. This sits inside the hammer. Photos to follow, and chrony results you will want to see at the end.   Spring ends on the hammer spring are horrific, so they got smoothed off.  New valve stem next to the broken factory one. Now I know I can successfully make them I might try slimming out the stem for better flow.  Delrin seat for hammer tension increase.  A couple of angles of the valve body. Trying to show the smoothed out angle for better air flow.   So what were the results? Prior to this work I had already fitted a hollow probe: Using 18 grn JSB 8 pumps I was getting 13.80 fpe. 12 pumps 16.11 fpe After the above works using 18 grn JSB 8 pumps - 15.71 fpe - 624 fps 10 pumps - 17.61 fpe - 661 fps I'm pretty impressed with that. I packed it in for the night, but will see if all the air has been dumped and will try 12 pumps tomorrow. Then accuracy needs to be tested.   |
Posted By: kruzaroad
Date Posted: 13 May 2023 at 9:01pm
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Dude that's a nice jump up in fpe. You must happy with the alterations. Great review throughly enjoying it Awsome detail photos. |
Posted By: Pauly5
Date Posted: 13 May 2023 at 9:24pm
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Glad you like it, It's been really enjoyable doing it. I've been making drawings with measurements so I can make more bits later without having to take it apart and measure things again. It also helps me figure out the order of operations.
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Posted By: RangerPete
Date Posted: 13 May 2023 at 9:48pm
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Very interesting thread. And you are lucky to have the machinery, and the knowledge, to be able to tinker and create 😉 Have you tried a few damaged skirts on that beveled probe yet? I’ll bet it works a treat! 😉 ------------- Walk quietly, but carry a big stick. |
Posted By: Billbobnz
Date Posted: 13 May 2023 at 10:02pm
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That... Is awesome. Fantastic results. |
Posted By: Pauly5
Date Posted: 13 May 2023 at 10:26pm
I will have a go at that next. I know the probe seats the pellet well as there are clear rifling marks on the skirt after pushing the bolt home.  |
Posted By: Pauly5
Date Posted: 15 May 2023 at 7:46am
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Quick update. 12 pumps = 19.16 fpe / 690 fps Bent pellet skirt testing to come.
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Posted By: Myson
Date Posted: 15 May 2023 at 8:02am
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Paul - you're an engineering genius!!! I wish I had your skills!  ------------- https://www.youtube.com/watch?v=eq7jVyBfFqE" rel="nofollow - https://www.youtube.com/watch?v=eq7jVyBfFqE Air Arms S510 US .22 Air Arms S410 .22 Weihrauch HW97KT .177 Weihrauch HW95 .177 |
Posted By: jwabfrog
Date Posted: 15 May 2023 at 8:44am
| Seriously impressive results, well done |
Posted By: Pauly5
Date Posted: 15 May 2023 at 9:06am
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I did try 15.89 grn pellets too, but the heavier pellets seem to hit a sweeter spot. 15.89 grn 12 pumps = 18.10 / 716 8 Pumps = 14.86 / 649 4 pumps = 9.46 / 516 What I really like is that this is a really good plinker too. A couple of pumps will give you enough power for quiet plinking.
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Posted By: kruzaroad
Date Posted: 15 May 2023 at 9:26am
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That's interesting I got 652fps average over 10shots which is 15fpe with hades 15.89gr out of box when first got 362.@8 pumps. Page 14 of you got to be out there to see,has all 10 chrono numbers. |
Posted By: J-S
Date Posted: 15 May 2023 at 2:45pm
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Looking like a good project! 4 pumps for 9fpe is nice power! ------------- https://www.instagram.com/js_airguns/" rel="nofollow - J S Airguns Air Arms TX200('s) Theoben Sirocco HW77 FWB 300s Webley Patriot One or two others... Current projects: Too many.. |
Posted By: RangerPete
Date Posted: 25 May 2023 at 9:10pm
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Hi Paul, Have u noticed and skirt “reformation” with your beveled probe? Makes me wonder if it might be worth making a dedicated “pellet skirt reformer press”?!?! Something like a small press that holds the damaged pellet by the waist, and a beveled rod is carefully pressed into the skirt to re form it back to round. 🤔 ------------- Walk quietly, but carry a big stick. |
Posted By: Pauly5
Date Posted: 25 May 2023 at 9:46pm
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Hi Pete, I did do some trials to see what sort of engagement was made on a good pellet, and I don't think that there is enough resistance from the barrel for the probe to push the pellet against. So while it won't straighten out a deformed skirt, it does look like it kind of seals inside the skirt. But it would be possible to make something that you drop the pellet into and push a probe into the rear of the pellet. I'm sure someone has tried it.
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Posted By: RangerPete
Date Posted: 25 May 2023 at 10:06pm
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Ja, what you say about the barrel not offering enough resistance to “grip” the pellet while the probe reforms a damaged skirt, makes perfect sence. I wonder if u can buy a mini press that would reform the skirt and at the same time swage a pellet. Maybe the ultra competitive competition guys have already come up with one to make sure every pellet is perfectly uniformly shaped and sized… Like powder burners who work out individual case volumes and weigh every case for uniformity, I’m sure a pellet swager/skirt uniformer would greatly increase the accuracy of any air gun. ------------- Walk quietly, but carry a big stick. |
Posted By: kruzaroad
Date Posted: 26 May 2023 at 8:24am
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It's called eyes and a vernier+, scales, or sorting your pellets. |
Posted By: Pauly5
Date Posted: 26 May 2023 at 9:01am
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I guess sorting first, visually and weighing would be the first step, then deal with the damaged skirt ones, or use them for practice. I have a brass pellet sizer that I used to use when shooting FT, but I don't think i'm good enough for it to make a difference anyway. I have also washed pellets in the past, applying a couple drops of lubricant to a tins worth. To be honest, I never spent enough time at a bench validating if there was ever any benefit. Now I just check for bent skirts before loading. If I was target shooting I would pre-sort and weigh.
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Posted By: jwabfrog
Date Posted: 26 May 2023 at 10:11am
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Tinbum sells pellet sizers - obviously only good for reducing pellet size. Link below https://www.airrifletuning.com/store/tbt-22-pellet-sizer/ I've also been interested in using lubricant but have never actually tried this - Napier sells prelubricated pellets which I think I might try as well as pellet lube: https://www.napieruk.com/products/power-pellets-22-target-tin-of-500-pellets https://www.trademe.co.nz/a/marketplace/sports/hunting-shooting/air-guns-parts/ammunition/listing/4147949924 https://www.napieruk.com/products/power-pellet-lube-10ml Lots of videos on youtube covering pellet cleaning and lubricating: https://www.youtube.com/watch?v=n9lNFKD3Q-0
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Posted By: kruzaroad
Date Posted: 26 May 2023 at 10:36am
| Head sizing and weighing reduces Flyers. I have no dought on that from target shooting on farm. |
Posted By: jwabfrog
Date Posted: 26 May 2023 at 11:01am
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PCP testing accuracy with damaged pellets: https://pneumaticdetonation.wordpress.com/2017/08/02/bent-pellet-skirts-and-accuracy/
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Posted By: kruzaroad
Date Posted: 26 May 2023 at 11:09am
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Yep not for hunting. He's also using a pcp which may be firing at good fpe. I wouldn't go by that myself as I've spent the time shooting unsorted pellets verses sorted and never got that good result with damaged pellets. Each to thier own. |
Posted By: Pauly5
Date Posted: 26 May 2023 at 8:52pm
| I don't know, but I'm guessing the more powerful the pcp, the better chance of the instant blast of pressure opening up a bent skirt. |
Posted By: RangerPete
Date Posted: 26 May 2023 at 10:07pm
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That sounds reasonable Paul, that a stronger blast or air has more chance of opening up a skirt. What have you guys tried as pellet lube? I know there are commercially avalible little bottles, but are there any home remidys that are cheaper or more easily avalible? I saw one guy on u tube, Tinys rifle stocks or something, (he shoots some impressive groups so he’s probably worth listening to) using a bicycle chain wax which is in a liquid form and dries fairly quickly. I think another guy was suggesting automatic transmission fluid… do u think that would produce dieseling? ------------- Walk quietly, but carry a big stick. |
Posted By: RangerPete
Date Posted: 26 May 2023 at 10:22pm
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Jwabfrog, I have tried the Napier power pellet lube once a long time ago. Unfortunately I didn’t do a before and after test to see if it actually improved accuracy and velocity, I just bought it and used it, and the little air arms shot beautifully, so I just kept on always using 4 or 5 drops of the lube in every new tin of pellets and kept on blissfully shooting… I’d like to get some more and give it a good “scientific” test. I’ll also do the same using the bicycle chain wax. ------------- Walk quietly, but carry a big stick. |
Posted By: Pauly5
Date Posted: 26 May 2023 at 10:47pm
| let us know what that chain wax product is. |
Posted By: RangerPete
Date Posted: 27 May 2023 at 7:35pm
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This is the one I have (I’m a bit of a bicycle nut). It is a liquid that dries and leaves a light white waxy residue. The Napier power pellet lube requires you drop 3 or 4 drops into a new tin of pellets, then close the lid and gently roll it over getting the lube evenly distributed through out the tin and over all the pellets. I’m going to try the same with the chain lube. The next time I’ve got the chrony set up I’ll do a full test, with and with out lube, group size at 30m etc…  ------------- Walk quietly, but carry a big stick. |
Posted By: kruzaroad
Date Posted: 27 May 2023 at 8:03pm
| Be interesting to see if it diesels. |
Posted By: GOODold308
Date Posted: 28 Aug 2024 at 8:37pm
| Great work and thread thread I'm definitely going to consider a hollowed out bolt for my cr600w build. |