Issue with my CO2 air pistol Walther CPM 1

john_almighty · Post by **john_almighty** » Tue Jun 12, 2012 3:46 pm

Hi all,
I have recently bought a used Walther CPM 1 which uses a CO2. I have never shot a co2 before this and learnt on a steyr lp10 compressed air gun. So please bear with me as i ask about something weird regarding my gun.

This happened today during evening when i was shooting at my home range which must be at around 25 c in temperature. I was consistently shooting an okish group and then suddenly on pellet just went down to 4 the ring and the sounds was also weird as if the gun was low on gas. My next shot just went straight to the floor without even making it that far and eventually the next shot didnot have any gas. When i weighed the cylinder it was still half full. I was taking a minute gap between shots so i dont think it was the usual issue with co2 guns. I dont think the temp is high enough to warrant me cooling the gun on an ice pack before shooting.

Now, i thought i should just bleed the cylinder value to see if it does have any gas left, and as i pushed the value, it started hissing pretty strongly and caused usual co2 frost so i reattached the same cylinder back on the pistol and it shot prefectly fine now. I am still scratching my head about this whole incident wondering what just happenned, this is unlike any of the usual issues i have read about co2 like shooting in hot environment or shooting too quickly.

Does anyone know what is going on.
Thanks
John

luftskytter · Post by **luftskytter** » Wed Jun 13, 2012 3:08 pm

Maybe you somehow got liquid CO2 into the valve?
Since the CPM1 has a vertical cylinder,
I guess there's no other protection against such a situation.

yana · Post by **yana** » Sun Jun 17, 2012 12:14 am

Sounds like it, temporarily, didnt take enough CO2.
I've had this with pcp pistols as well.(which was a regulator issue)
Indeed, removing, and re attaching cilinder can help, but wont fix the problem.
Probably a valve leak or sticky valve I think.

john_almighty · Post by **john_almighty** » Sun Jun 17, 2012 5:47 am

Thanks yana and luftskytter for you replies. I didnot have the issue anymore yet but still working on the issue. I had just filled the cylinder and noticed that screwing it completely was a bit difficult, someone mentioned that the seals get swollen due to cold. So maybe the fit was not enough and caused some issue. I have been now filling the cylinders and leaving it for 30 mins before using it. Also did notice i needed considerably less effort to fully screw them back on. Lets hope this sorted it. Would hate to fire a 5 because of this issue in a match.

luftskytter · Post by **luftskytter** » Sun Jun 17, 2012 8:21 am

I'm not sure I understood everything right,
but just some standard advice:

I normally leave the cylinder in the freezer for a while before filling.
This makes it possible to overfill so that there there i practically no gas (only liquid CO2) in the cylinder. This may jam the mechanism. You should weigh the cylinder to check for a correct fill: I normally go for a couple of grammes below max weight stamped on the cylinder.
If you got too much, bleed a little gas by pushing the cylinder valve.

Dunno if this is any help.

Rover · Post by **Rover** » Sun Jun 17, 2012 9:59 am

The above post has it right. It is particularly noticeable here in the scorching desert.

I stopped cooling my cylinder before filling and it took more than enough CO2 to shoot a couple of matches without any hassles.

john_almighty · Post by **john_almighty** » Sun Jun 17, 2012 12:56 pm

Apologies luftskytter, reading my post now, i realise how garbled it sounds. Should refrain from replying on a blackberry.

What i meant was, when i fill the cylinder with gas, usually when i am unscrewing the cylinder after the fill from the main co2 tank, there is some residual co2 in the filler valve which just fizzes out making the mouth of my gun cylinder super cold.

Now if i try to screw this cold cylinder on my gun, it takes a lot of effort to fully screw it on and i think i might not be fully screwing it in place. I reckon this might have something to do with the swollen o- ring in the cylinder due to the cold. I have noticed the same cylinder is very easy to screw back on if i leave it for some time.

I am assuming something was going wrong here due to the not fully screwing the cylinder in place. Or it could be due to spilling of co2 from the full cylinder into the valve. For the time being it seems whatever was causing the issue is not happening if i let the cylinder warm up a bit after a fill rather than screwing them on instantly.

Thanks rover for your reply, if my current theory fails, i would assume it has to do with liquid co2 in valve and refrain from cooling cylinder before a fill.actually, i would give your method a try once the cylinder empties. After all london is not sahara so maybe the freezing before filling is just overdoing it.