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CA M24 w/ advanced cylinder kit low fps!!

4275 Views 15 Replies 6 Participants Last post by  trevorcomstock
Hey guys
I installed the Advanced Cylinder kit in my CA M24 and played 2 games with it, after that I decided to open the cylinder and clean it.

After opening I found some metal chips on the piston and nozzle, I clean everything, I super glued the buffer o-ring on the nozzle, cleaned/lubed everything and assemble it.

This happened 2 months ago, I didn't use it in the mean time.
I got a new chrono and I decided to test some of my guns, all went well till I tested the M24! I had some .40's in the mag and thought "What the hell, I'll test it with .40's!" The FPS reading shock me!! 178fps!!!! :ashamed:

This is WAY lower than the 500fps at the chrono testing at the field!

I've tested the cylinder/piston and there's ~1mm play! Is that normal?
I'm thinking to test some new o-rings for the piston head for start.

Do you have any suggestions?:shrug:

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Not sure how the rules are where you play, but where I play the guns are chronoed using .20 gram bb's.
If you have lighter bb's try using them when you chrono, however with the amount of play you have between the cylinder and piston you could also have an airleak. Try fixing that either with tefflon tape or new o-rings then re-chrono using a lighter gram bb.
I had an o-ring fall off of the piston and was obscuring the exit of air from the cylinder head. Open it back up and look to see if that's the case.
Thank you ...
I'll try to change the o ring first

We also test our guns with .20g bbs and the initial chrono was with .20s.

I replaced all the o-rings in the cylinder the gun now shoots above 400fps w/ .25s( I don't have any .20 ATM!).
There's a fluctuation though... It shoots from 400 to 480 fps!!
I tried to put teflon on the nozzle threads and under the piston head o-ring but I failed(the o-ring chipped off from the threads when I pushed in)!

The o-ring in the piston head seems to be OK so does the nozzle oring, do you have any suggestions?
Also the spring, piston and nozzle from the stock cylinder seems to be the same! Only the material on the cylinder is different (stock aluminum, advanced kit steel).

Another thing I noticed is the cylinder has significantly wear the set pin of the trigger group! Would an APS2 trigger group fit the CA M24?

A stock APS trigger should fit in as almost a drop in. A zero trigger requires modification to the trigger guard on the M24. For the modification, you'll need a dremmel, a drill, and about 30 minutes.
You could still have an airleak somewhere. If not the piston head or the nozzle e air could be escaping through the hopup bucking. Check and see if that's worn down a lot. If it seems ok here's a little DIY mod you can do to seal up any possible leaks.
Thank you for that...

I'd like to know if there's a way to check for leaks the cylinder nozzle.

I take a screwdriver or similar implement and manually pull the piston back while holding my finger over the nozzle end. It's difficult at first but can be done. Make sure you watch the edges on the cylinder hole though. I found that mine had some pretty bad burrs on it which was able to cut my finger open when I went to do this test.

Since then I deburred the piss out of that opening using an abrasive pad I obtained from work.
Thanks man... It's going to be very hard to do that though!

That hole on the cylinder damaged the set pin of the trigger group!

I might buy the PDI trigger group as a replacement. Or take to a machinist to see if he can copy that.

EDIT: Forgot to add that I installed a very rare Sheriff steel handle to it as the stock begin to break down!

I bought the CA steel bolt handle for 45. I didn't trust the original either. Although the steel one had the same problems with the ball bearings and ended up tearing up the holes. I just shoved some string in there to give it some resistance when lifting the bolt handle.
LoL I bought the Sheriff for $25 second hand but in excellent shape.
I didn't install the ball bearings and springs, I just put a piece of foam from a car seat!
It's working good and now the end cap of the handle doesn't unscrew!!

I don't know if I find some time to work on the rifle today... I can't wait to finish it and start working on something else.

I stripped it completely today again... Build it up completely but I couldn't test it... So the results tomorrow...!

I can't wait to be honest!

Finally I've finished it...
The average fps are 491.3fps and the max fluctuation is 5.6fps!
I'm pretty happy with that.

Thanks for all your help guys
George When You will be able i need you to talk via the skype cause i just got a HIT on my CA M24 too :)

Johny :)
Anti-Static Bag

Wrap an single layer of an anti-static or mylar bag around the piston when you insert it into the cylinder. No damage can happen to the o-ring (or the more vulnerable y-ring or x-ring.) Then just hold it down with a probe through the nozzle (as described) and remove the bag. Perfect seal every time.
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