CR600W - Mediocre power after common mods

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   Sounds like you were on the right track for good power, just to check though when you opened up the TP hole you also matched the valve, breech and barrel to the same diameter?

Pauly is on the right track to bring up pellet weight too, my testing at 18 fpe was always with heavy pellets and warm weather. The .25 cal one I built for Zooboy ended up about 22fpe from memory.

Dropping the power back if necessary is just a matter of less HST or a lighter hammer, doesn't matter if the valve is still hogged out for max volume.

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Mintie Members Profile Send Private Message Find Members Posts Add to Buddy List Member Joined: 18 Feb 2017 Location: Hawkes Bay Status: Offline Posts: 48	Post Options Post Reply Quote Mintie Report Post Thanks(0) Quote Reply Topic: CR600W - Mediocre power after common mods Posted: 29 Jan 2025 at 3:26pm
	Sounds like you were on the right track for good power, just to check though when you opened up the TP hole you also matched the valve, breech and barrel to the same diameter? Pauly is on the right track to bring up pellet weight too, my testing at 18 fpe was always with heavy pellets and warm weather. The .25 cal one I built for Zooboy ended up about 22fpe from memory. Dropping the power back if necessary is just a matter of less HST or a lighter hammer, doesn't matter if the valve is still hogged out for max volume.

jwabfrog Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 13 Nov 2021 Location: Thames Status: Offline Posts: 152	Post Options Post Reply Quote jwabfrog Report Post Thanks(1) Quote Reply Posted: 23 Jan 2025 at 9:38am
	Lol Pauly, I think we should all be adopting / dialing minute of rabbit. Many a slug / pellet wasted chasing the 6mm hole at 100yds!

Loud_Whisper Members Profile Send Private Message Find Members Posts Add to Buddy List Member Joined: 29 Sep 2024 Location: Auckland Status: Offline Posts: 13	Post Options Post Reply Quote Loud_Whisper Report Post Thanks(0) Quote Reply Posted: 22 Jan 2025 at 9:54pm
	Interesting! I'm almost relieved I don't have a PCP simply for the fact that I'd go broke because I'd enjoy tuning it so much! Keeping in mind this will be used mostly only for mynas and pinking, I think I'll return the valve spring to standard tension, find some cheap ammo that works, and move on to getting the next one in the fleet dialled (Hatsan 135 springer)

Pauly5 Members Profile Send Private Message Find Members Posts Add to Buddy List Forum Moderator Joined: 11 Mar 2013 Location: Titahi Bay Status: Offline Posts: 1523	Post Options Post Reply Quote Pauly5 Report Post Thanks(0) Quote Reply Posted: 22 Jan 2025 at 12:25pm
	From my own experience, you do need to be prepared to waste quite a few pellets to achieve what I would call the "two stages" of tuning. 1, to get hammer and reg balancing for efficiency and accuracy, and then 2, to get harmonic tuning for accuracy. The second part is harder depending on your gun and this is what attracted me to the impact as it had a valve adjuster. Typically you have reg pressure and hammer tension, but then you have the dwell time of how long the valve stays open. This can be finely tuned by increasing or decreasing valve return spring tension. Once you have that reg/hammer balance shoot a couple of groups at 30 and 50 m. If they are good and tight leave it. You can tighten the groups by subtly changing the valve and this is where the impact is good in that you can do this externally. Adjust valve a touch, shoot groups, and so on until your groups tighten more. But of course being fixated on a 6 mm hole at 100m is chasing your tail. I stick to minute of rabbit head personally.

jwabfrog Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 13 Nov 2021 Location: Thames Status: Offline Posts: 152	Post Options Post Reply Quote jwabfrog Report Post Thanks(0) Quote Reply Posted: 22 Jan 2025 at 10:41am
	My understanding of tuning a PCP after reading and watching many youtube videos is to start with max hammer spring tension and then steadily increase reg pressure to get slightly more than your target fps. Then reduce the hammer tension to drop to your target. This results in a high efficiency tune on the shoulder of the fps vs hammer tension curve i.e. minimises wasted air and helps reduce fps variation. This is a good summary: https://www.airgunnation.com/threads/how-to-do-a-basic-regulated-pcp-tune-the-95-tune-plus-m3-tuning-simplified.1242157/

RangerPete Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 19 Apr 2023 Location: Cambridge. Status: Offline Posts: 956	Post Options Post Reply Quote RangerPete Report Post Thanks(0) Quote Reply Posted: 20 Jan 2025 at 7:07pm
	Sometimes you got to go backwards to go forwards.... Case in point is I wanted to lower the FPE of one of my pcp rifles a few days ago, so I lowered the reg pressure, thinking if the rifle is being fed less air (lower pressure) the fps will drop and the FPE will go down, right? Lowered the reg pressure and the fps and FPE went UP!!! Left me scratching my head. Tried it again and lowered the reg further, and the fps and FPE went UP, again!!! Contacted Pauly for some brain storming and sound advise and we figured out that the lower pressure behind the valve was allowing it to stay open for longer (before pushing it closed from behind). So the lower pressure, longer shot of air was causing higher velocitys. So I opened the reg back up to where I had started, then opened it up another 1/16th of a turn, so it was now running 9bar higher then when I started (60bar up to 69bar) and guess what... velocitys and FPE went down!!! With more pressure behind the valve, it was closing faster, letting out less air (although at a slightly higher pressure) and my FPE dropped and with a little more reg pressure, I got it to where I wanted it Fuzzy logic, but once you understand whats happening inside the gun, it all makes sense.
	Walk quietly, but carry a big stick.

Loud_Whisper Members Profile Send Private Message Find Members Posts Add to Buddy List Member Joined: 29 Sep 2024 Location: Auckland Status: Offline Posts: 13	Post Options Post Reply Quote Loud_Whisper Report Post Thanks(0) Quote Reply Posted: 20 Jan 2025 at 2:24pm
	Wow that is some low power and very reasonable distances. Big respect! Its So counter intuitive to want to go down, but makes so much sense when I already have bigbois for other jobs. Yep lots of fun indeed, and a few more non power mode lined up too. Just dropped two mynas this morning and about to head down and check the damage! Thanks all.

kruzaroad Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 03 Jul 2022 Location: Hastings 4 now Status: Offline Posts: 2468	Post Options Post Reply Quote kruzaroad Report Post Thanks(0) Quote Reply Posted: 19 Jan 2025 at 10:45pm
	My 1322 is only about 6fpe and snots out starling and mynar quite happily to 30m. Has taken a starling at 50m approx. Dropped a possum at about 2ft so I imagine your going to be getting a lot of pass thru on birds at those fpe. Should do the job fine. You've obviously had a bit of fun working on it, so a win all round id say

Loud_Whisper Members Profile Send Private Message Find Members Posts Add to Buddy List Member Joined: 29 Sep 2024 Location: Auckland Status: Offline Posts: 13	Post Options Post Reply Quote Loud_Whisper Report Post Thanks(0) Quote Reply Posted: 19 Jan 2025 at 10:08pm
	Thanks guys. Forgot to mention that deepening the valve did indeed decrease its spring tension, so some impact there as well. Chrono again today a few times throughout the day and was around 560-570fps in the warmest part of the day. To be honest I probably need to forget trying to get too much power out of this one as I'll only ever use it for birds and have bigger badder things for other pests (Hatsan 135QE and Gamo G Magnum for possums & wallabies etc) Next step will be to see if I can get it a bit quieter without loosing "too much" velocity, and to try some heavier pellets still just to see what happens. Next stop will be seeing if I can balance out the extra cooling - possibly backing off the gas volume in favour of some cleverer porting into the barrel. Edited by Loud_Whisper - 19 Jan 2025 at 10:34pm

Pauly5 Members Profile Send Private Message Find Members Posts Add to Buddy List Forum Moderator Joined: 11 Mar 2013 Location: Titahi Bay Status: Offline Posts: 1523	Post Options Post Reply Quote Pauly5 Report Post Thanks(0) Quote Reply Posted: 19 Jan 2025 at 10:06am
	Hmm, I have modded one, but didn't go for any great power increase. Looks like you've done a good job so far. Did you soften the valve spring so it stays open a bit longer? I see Mintie lengthened the valve spring seat so the result was it being softer. Having more volume and the opened transfer port would be my main focus and I think using a heavier pellet is key for CO2. Also make sure all the O rings around the TP are good too, as any leakage there will kill power.