OK, update, think I will put it all here, sorry Marcel_01.
So, no the BCG is not doing dbl duty, this lower has been it’s home for several years, just wanted to change the 3 AR in the family to a 300 (the other two being my first build, abit with a complete upper from PSA, the second being my wife’s - which I am forbidden from touching). While not eliminating the possibility a new BCG is needed, I have too much $ in this one-off build at this point, I will have to wait.
This was a new 300 upper from PSA.
SO I broken the gun down, for a good cleaning. I checked the BCG for possible ring leakage, along the verifying the gas system, it passed. Then broke down the BCG for thorough cleaning, reassembled, tested the rings again, still good (test the rings, stand the assembled BCG on end, if the rings are not holding then it will compress under it’s own weight, least according to Brownells). Dbl-checked the ejector as well as looked for any corrosion, it was good.
Checked the alignment of the gas tube end, checked for wear (not sure I would see anything after just 100 rounds, but checked anyway. Inserted the BCG & CH, ran it back and forth checking that it seeded correctly, all looked good.
I did not break-down the upper to examine the gas block, a time and tools thing, and not comfortable with the upper disassembly and reassembly, yet. So kind of trusting PSA that the GB is aligned properly.
As far as the Magpul 300 mags, I think they are good for me, did not seem to have any issues when I cycled through them on the range. Forgot to mention I also used a 10-rd 5.56 msg while I was zeroing the gun, no problems there either. The one failure to feed was due to stuck casing in the ejection port when the bolt came forward. I have several 5.56 (Magpul) mags I can test out next range trip.
I still don’t know if I am under-gassed or over-gassed as I did not note where the casings were landing on my range trip.
I tried to check PSA web site to read the specs on my upper gas block, because I do not remember it being adjustable but the web link is no longer valid (which I also find unusual since it was ordered in January this year, oh well).
The 300 is now reassembled in same condition as when I experienced the ejection issue with exception of an added H2 buffer. And I made a mistake in my original post, the buffer spring and buffer were from a B5 Stock I had on hand (new one) because I wanted the QD mount which the Magpul didn’t have ability for (old Magpul, sling slots not QD).
Next time on range will note:
- where casings are landing
- will try a mix of Msgpul 300 and Magpul 5.56 mags
- will pay attention to being “gassed” (blowback I guess)
- still usonmg supersonic ammo, this time S&B 124gr 300 (ran out of AAC 125gr)
