I did. He had it all.
BUT - i think i found the culprit!
After spending some quality time with both BCG's after dinner, I noticed the original colt bolt has chamfers on three sides of the lug teeth (closest to carrier). The new bolt is chamfered only on the tops, and the sides (where the other chamfers should be) are very sharp.
MPI brand lug (bolt?) - no idea, haven't look them up yet.
Otherwise, after thorough cleaning/drying the only wear i see on the new BCG is very light scuffing on the sides of the base of the gas tube fitting - even on both sides. The old BCG is the same. -assuming there's wiggle room here.
As the seizure occurred real close to full lockup - much (almost exactly) like Picton describes, I'm thinking those hard edges just don't slide nice against the face of the lugs in the barrel.
I'd assume, if i could see the fronts of those barrel lugs, i'd see a little marring...if in fact this is the issue. But, I see no shavings or filings.
Seeing as enbloc brought up power tools
, I'm not sure I see any harm in stroking a super fine flat diamond hone on those sharp edges to ease them out?
It also seems as though the channel that supports the cam pin could use a little breaking in compared to the old one but, my finger still moves the lug in easily.
Thoughts?
ETA: made some edits as I pick up the terminologies.