Air chief .22 cr600w co2

Hey guys,
I understand these air rifles are a common one for people to do a few internal mods on to get a little more power etc.
Was wondering if anybody on here has worked on one as any info from here is probably more relevant than any from overseas. So far I have found it reasonably accurate for what it is but of course any little tips/tweaks that could be done to improve things other than trying different pellets is always a good thing right?
Seeing as its nice and quiet already its a good way to get a bit of trigger time while in town for a bit of practice.

@Mintie

Happy to help and local, I have tuned up quite a few of the CR600s

@Mintie cheers for the offer. Where would be the best place to start on it in terms of bang for buck(time input) .
Would be keen to be able to do it myself but as always a bit of guidance from the more experienced people is always so valuable

The mods for them are pretty simple, increase valve volume ( by cutting a few threads off off front half and boring it out a little) and increase the ID of the transfer port from the valve to the barrel - this means increasing the port diameter in the valve, transfer port itself, breech and barrel. If you want you can also take off a few mm from the rear half of the valve where the hammer hits, that allows the hammer to hit the valve stem just a little bit harder - oh and polisher the hammer so it travels faster in the tube. You can then play with hammer weight and hammer spring tension to get it all balanced nicely, of and polish the trigger sear too.

These rifles can get up to about 18fpe on a decent tune which is about double the factory power. I even made one up for a friend in .25 cal that was pushing close to 22fpe from memory.

Thank you so much for the wealth of information. In terms of increasing the ID of the ports you mentioned, is there a size to increase them to or is it a percentage based increase? Also I'm guessing doing these mods also makes a co2 cannister empty considerably quicker too?
Cheers
George

I open it up to 4.5mm all the way through. Just checked back through my old posts on the NZ Airgunners Facebook group and I got one of these up to 20.5 fpe in .22 cal when shooting very heavy pellets so they can produce good power!

The barrel crown may need to be redone as well, quite a few I've come across have been ugly, this group of photos show the before and after barrel crown and shows what the valve halves look like once modded.

Attachment 184171

What a legend @Mintie I now know how I will be working on for a little while now!
How would I go about taking the front open sight off the barrel? As I plan on keeping a small scope on this one anyway. Also I noticed there is a little bit of movement inside the barrel band, is this something worth shimming up to a tight fit?
I think ill try all the other things you mentioned first before cutting down the valve halves as it looks a little like a job for a lathe which I don't have. Is recrowning something that can be done with hand tools or also a lathe job?
Again thanks a heap for the help!

Quote:

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Originally Posted by cheeseclip

What a legend @Mintie I now know how I will be working on for a little while now!
How would I go about taking the front open sight off the barrel? As I plan on keeping a small scope on this one anyway. Also I noticed there is a little bit of movement inside the barrel band, is this something worth shimming up to a tight fit?
I think ill try all the other things you mentioned first before cutting down the valve halves as it looks a little like a job for a lathe which I don't have. Is recrowning something that can be done with hand tools or also a lathe job?
Again thanks a heap for the help!

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I have a lathe and can help out with it all, just gotta find some free time is all!