When I got my m4 it didn't start acting up until right around 200 shots.
Did a bunch of reading about it and what was tried to correct it
Seen people adding nylon and delrin washers to support that o ring.
Problem is when doing so the o ring drags worse
And the warmer it gets from the valve rod drag the worse it gets.
2nd thing was reg creep not to bad but maybe 4-5 bar in 24 hrs.
Contacted a relative who makes o rings from a to z from automotive to high pressure gasses and numatics.
Took the gun apart brought him the valve rod and plenum tube
He put them into a jig in the lab to replicate the gun firing and recorded the o ring surface temp
The rod temp rod speed talk about getting to the root of the issue LOL he is something to watch.
3 days later he came up with the compounds that were in the original o ring which he said wasn't even close according to him.
He had I'd say 200 maybe more maybe less different compound o rings he went through.
Also changed the size of the i think the orig is 5.5x1.5 that changed to 1.87
He also said if I wanted this to work the best it could I'd have to coat the valve rod.
He does coating to these high pressure 22000psi linear solenoid pintle valves
He said there is almost zero co officiant drag I said isn't that going to add to the od
He already had it figured lol.
Anyhow my shot counts are no more than 4 fps apart don't matter hot cold can sit2448 hrs.
Another thing was matching the regulater washer thickness
Matching them polishing them took all the sharp edges off and had him put that coating on them.
I also purchased that plenum tube that a member is having made as that really will do justice with suporting the o ring.
so far after all this r&d the gun shoots really well reg recovers within 4 seconds no more than 2 bar creep wether it sits for day or 2
I have my reg set at 128 shooting 30-32 aea or h&n slugs in the 600mm barrel at 970s
Little heavier in the 700mm but slower fps 930s and they group well at 75 yds nickel to quarter size groups .
Yeah it was some work but I enjoy such a challenge have been a gear head for 40+ yrs.
So tinkering is my thing.
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