Tuning R5M pop and puff

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Bogey47

Bogey47

Member
Jul 21, 2017
140
2
Savannah, Ga. United States
My R5M is driving me nuts. Every time I fire it I hear a loud pop and get a puff of air in my face. Brian says it sounds like I have the wedge under the air tube installed improperly. I have taken the gun apart 15-20 times,reinstalled the wedge as directed in Brian’s video and as appears on the schematic. No luck. The air tube seems to be as far up as it can go. It has no “play”. The o-ring appears to be fine.

Does anyone know a solution other than send it back to Brian?




 
Could be any of these seals.

1. Breach o-ring

2. Transfer port o-ring

3. one or both of the o-rings on the barrel.

You can orient the wedge in 2 different ways so check that too.

4. Is your bolt unlocking when fired?

I had a leak and devise a test, closing the breach and using an air gun nozzle from a air compressor to pressurize the barrel from the muzzle end. The leak I had was one of the barrel o-rings. However even after fixing that if I increased the pressure beyond 40 PSI I could hear another leak. I suspect it may be the breach o-ring because I lubed it while many say don't do that.


 
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In regards to that clear plastic ring that you found, I know that's not an OEM part, however, I do recall one of the members here (I believe DavidSNG) used one to fix the same problem that you have. I know you said that the breech o-ring looks fine but did you try changing it to a new one. If you have some new o-rings, I would just change it out. Maybe add some silicone to the breech o-ring if you haven't done so. Also check the transfer port o-ring and just replace it. Did you ever remove the barrel? If you have, you might want to replace the barrel sleeve o-rings.

Edit: I had this typed out earlier and didn't post it until now and see others have posted some solutions as well.
 
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Yeah, I did the thin plastic donut thing too at first (R5 / .30). Then, I finally put the brass piece on my lathe and removed some material so that it would seal properly. 

A better hack that I found in between was getting the brass piece nice and sticky with synthetic grease, and sticking a ~14-15 x 1mm o-ring around the breech o-ring. Then I re-installed the bolt housing (sandwiching it in place). That also worked very well.
 
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Okay, I replaced o-rings everywhere, transfer port ,breach,barrel sleeve,and regulator. Hooray the pop and puff is gone. Now my r5m is sending 18.1 JSBs down range at a sizzling 441 FPS . I can’t win. Help!

I only shot three mags,is it possible that the reg needs to adjust to the new o- rings. Maybe the new rings were worse than the old ones?

My Wildcat is now up and shooting after a pellet found its way to the transfer port.

Hey things are good. I grabbed my 300S and a beer this afternoon and shot a clean ten dimes target. At least something works.Happy shooting.
 
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What was wrong with the brass piece? Was it not Square to the bore? Was it finished poorly? Won't cutting it down going to make it possibly too short and limit the compression the O-ring?
Click to expand...

The latter. It was a few thousandths of an inch too long, so tightening down the breech block didn't create a proper seal with the factory 7x3mm o-ring. Removing some of the brass material allowed for the breech housing to be snugged further, allowing the o-ring to do its job.
 
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