OK gang hoping for some direction here. Working with an Historic Arms semi MKII in .308. I have a .303 bolt in there with a .308 extractor. (casings are a bit "loose" in the bolt face when clipped in by the extractor. ANYWAY been having trouble with failures to extract/eject. Every few rounds having the empty case get stuck in the receiver and mucking up the loading of the next round. We have tried drilling out the gas port in the regulator to match the .15 of the case port in the barrel = no real change. Tried clipping off the recoil spring in the buttstock down to about 1/2 its original length. = shorter we cut the spring, the worse the problem got. With the original spring we could get 5 to 10 rounds at a time and with the lighter spring it jammed every other round or maybe got 2-3 rounds at a time.

Now when I hand cycle the rounds, it functions perfectly. But fails when under gas pressure from being fired. Doesn't change with mag (using ZB 39 (curved) mags from when the gun was originally chambered in 54R)
Also observed that both with hand and operational cycling when fired, some of the rounds "flick" out the bottom with reasonable force while others drop out with very little force. Ideas as to what could be causing this? Ideas to try to fix?

Thanks, feel free to PM me to chat about it.