Fired 60 rounds, three different types of ammo and four magazines. New extractor, ejector and spring, thourough cleaning of entire gas system. Can't cycle 4 rounds in a row.
I called Jame River Armory, very friendly. We went over a lot of items. Diagnosed as either gas piston or gas cylinder. They suggested Sadlak NM with coating. On order. Will update after installing and test firing. It is very accurate, I must say. USA2
Hi Mass Patriot,
Don't waste your time or money getting another piston, that is not it, providing you did get the right small drill bit and clean the tail of all carbon fouling too. It is not your gas cylinder either, unless the rear ring that holds the spindle valve port tight to the barrel is leaking massive amounts of gas and is shaky loose. Which reminds me, make sure your spindle valve screwdriver slot is straight up and down, vertical, when holding the rifle horizontal, not partially sideways or horizontal. In other words, perpendicular to the barrel. 90 degrees, not 75 or 80
That would be easy to spot, either condition above. One because there would be black marks from the gas leaking around the ring, and etching, and the other because it would be rattling loose.
In all the years of inspecting hundreds and hundreds of gas cylinders with ball micrometers and snap gauges, I've only seen one that was worn out from firing....and have never seen a g.i. piston worn out....and I've seen some rough ones.
If you didn't mount a scope and put too long of a machine bolt in and it is not dragging on the left bolt locking lug and robbing gas, and the left helix side wall cuts aren't interfering with bolt travel, there are only two things that can cause this issue.
One, I already covered before is the chamber reaming job being too rough and hanging brass until enough gas is robbed to not allow a complete cycle.
Two, is the receiver bridge cut for firing pin retraction.
You can visibly check the first by looking at the chamber with a good bent neck light with the trigger group and bolt out of the way.
You can check the second by removing the trigger group and taking the action out of the stock and standing it on the flash suppressor, barrel down and heel straight up like a tomato stake. Leave everything else in the action.
With bolt closed in battery, reach under the receiver heel and push the firing pin forward, as if your finger were the hammer hitting it, then hold the heel with that hand and with your other hand, take one finger and pull gently on the op rod handle and watch the firing pin and see if it rotates and will allow the bolt to open. If it takes a lot of force or more than one finger, the cut is wrong or insufficient to allow retraction under normal and violent retraction.
The tail of your firing pin and the bridge will tell the tale and show gouges or bad wear characteristics on it. Read, shiny spots, cuts, scrapes, etc.etc....You can polish them up and it may help. If the cut is wrong, very common by the way, it can be fixed easily.
If it's a rough chamber or too tight a headspace, or combination of both, it will need to be fixed by a professional. Post pics of the receiver bridge from the rear and underneath it, looking forward with the bolt and trigger group out of the way. If it is the problem, I can identify it. So can username Ironworker here. He has an excellent thread in the Gunsmithing sub-forum here that you can compare yours to.
Let me know what you find........rip