Erratic Ejection Pattern

[JoeBobJoe]

I got a midlenth 16" that's got me stumped. It has erratic ejection1:30 to 5:00, & throwing brass lazily only 3 feet or less.. It's has periodic bolt over base malfunctions 2or 3 per mag. After hundreds or rounds through different mags & testing on other carbine lowers & 3 buffers, then tearing down gas system checking for leaks & misaligned gas block which is pinned. I opened gas port it was .063, to.075... test again....to now a huge .093. I know it's over gassed now, but it still ejecting the same erratic ejection 1:30 to 5:00 & only 3 feet.
So today I put it on a standard A2 rifle lower & got a crisp, 3 o'clock ejection pattern throwing brass about 7 feet. BTW the case head looks clean no hard extraction marks, primers are not flattering out or piercing primers.
Why won't it run on a carbine lower with a 4oz T2 buffer or a H1 or standard carbine buffer. It did best with standard before I opened it up but still had weak & erratic ejection and bolt over base ftf.
Im going to try my lower on a friend's midlenth upper, this week. I can't see it being the lower but who knows.
Did I go from under gassed to over gassed with same exact symptoms? Or am I missing something.
My next thing is just try a H3 or 9mm blowback buffer, in my lower.
Any insight will be appreciated, Thank You.

[dmd08]

You've tried ammo, mags, buffers, opening the gas port WAY too big and entirely different lowers. But you haven't given your BCG a look?

[HKGuns]

You've tried ammo, mags, buffers, opening the gas port WAY too big and entirely different lowers. But you haven't given your BCG a look?

Agreed.

I would remove and clean the ejector, replace the ejector spring and replace the extractor. My simple mind can envision no sceneario that involves the lower. That is pretty much all you have left.

[JoeBobJoe]

Agreed.

I would remove and clean the ejector, replace the ejector spring and replace the extractor. My simple mind can envision no sceneario that involves the lower. That is pretty much all you have left.

I forget to mention that I tried 2 different BCG a newer Spikes & older PSA premium, both work in other uppers.
I even removed the O-ring while at the range after I checked the extractor spring & ejector.
I'm stumped but not beat. If I have to I'll put a rifle receiver extension & buffer on the lower.
That's cheaper & easier than a new barrel.

[JoeBobJoe]

You've tried ammo, mags, buffers, opening the gas port WAY too big and entirely different lowers. But you haven't given your BCG a look?

I forget to mention it. Yeah, I tried 2 BCGs that work 100% & checked gas rings, extractor tension, & ejector while at range & home.. The cases look clean &:eject fine with a rifle lower, just not the carbine lower. I even replaced the FCG with a older spare hammer & trigger that I ran before, to make sure it wasn't the hammer out of spec. & slowing the carrier speed.
I only opened gas port because it was a bit tight, then more so out of frustration. The lower has ran other uppers in the past. I started thinking tolerance stacking. I was ready to get another barrel but may just run a rifle buffer tube, It just don't make sense,. A carbine or rifle lower should be interchangeable, on most uppers. Why does it run on a rifle buffer system & not a carbine, that stumped me.

[markm]

Two things.

1. Overgassing won't cause head swipes, so no surprise there. and

2. Do you happen to have one of those God Damned Retarded Springco buffer springs? I tried one of those once and totally effed up a decent running carbine.

last possibility is there's a poorly button rifled barrel that's got tight or overbore spots.. and it just needs to be replaced. pin gauging the bore would tell you if that is possibly and issue.

[1168]

I somehow doubt its the ammo, but what ammo is being used? A faulty or damaged ejector would have been my first thought.

[markm]

I somehow doubt its the ammo, but what ammo is being used? A faulty or damaged ejector would have been my first thought.

Could be ejector too. He was running IMI ammo in the original thread.

[JoeBobJoe]

Two things.

1. Overgassing won't cause head swipes, so no surprise there. and

2. Do you happen to have one of those God Damned Retarded Springco buffer springs? I tried one of those once and totally effed up a decent running carbine.

last possibility is there's a poorly button rifled barrel that's got tight or overbore spots.. and it just needs to be replaced. pin gauging the bore would tell you if that is possibly and issue.

I tried standard PH 17 -7 SS & a Damage Industry enhanced CS buffer spring, 3 buffer weights just not a H3.
The recoil feels sluggish, bolt over base stoppages but it locks back on empty mag every time. IDK.
Thanks for listening.

[JoeBobJoe]

IMI 62 & 55 grain, & 62 grain LC.