I been around for a while, built the first AR15 in 1977, and have found that some bolt carrier, upper receiver, barrel, lower combinations simply won't work together. Today i had a LMT upper on a EA arms lower, with an ICE arms M16 bolt carrier. Jammed every other round. Took a DPMS semi-auto bolt carrier from another AR and ran perfect.  Placed the ICE bolt carrier in the other AR (Superior lower) and functioned perfect. Mags are high quality and not the cause of the jamming. I have had this happen a couple of times lately. Anyone else had this problem?

Where did you get the lower & parts in 1977?

Functional problems, no.
Fitting problems between uppers and lowers, yes
With range of tolerances and quality we are seeing nothing would be a surprise.

I have been making parts rifles since the early 1980's a general rule of thumb has always been that not all combinations of parts work in all rifles. I've had a lot of different scenarios where a build just will not cycle properly. They just don't. Find the right combination of parts and you're good. -W

Wow, you built the first AR15??

Got locked out of the site for several days. Couldn't recall e-mail from several years ago. In answer to your question, B&H Service (Old Sarge) in Natalia, Texas had plenty of M16 parts. I was in Austin, TX at the time drove down to his place to check it out. You could build a CAR15 for about $300.00.  Was able to hang out there for a while. They had a huge crate of de-milled M60 machine guns, wish I had picked up a parts kit. Other than that gunshows were about the only other source. Vaughn Jonson (EA Lowers) was first attempting to machine AR15 receivers in Krotsprings, Louisiana. Aftermarket lowers were just becoming available.

Woops that did not come out right. No, my first AR15. Which was a CAR15 with a 11 inch barrel with welded 5 1/2 inch flash hider.

Well, now you're immortalized:

http://www.feinsteinproject.org/misc/shortHistoryOfFeinsteinProject.html