ok, specs:
Fulton Armory a2 upper
Windham Weaponry 20" barrel kit
range Tool "no rollmark" lower w A2 stock/tube and rifle spring-buffer
PSA BCG

built and checked headspace ok

first fire with one round in a brownells 20 round mag- fired as normal and held back open bolt as normal

loaded a ASC GI style 30 round mag and fired about 8-10 rounds [ my brother] then he handed rifle to me and I continued to fire, and after another 5 rounds or, so it failed to feed.
I found the bolt against the round and the bullet tip at the bottom of the upper, the round was on the left side of the mag.  dropped the mag, and picked up a Magpul mag and inserted it, it loaded the first round, but again FTF the "next" left side round, again with the tip against the upper just below the feed ramp.
examination shows that "maybe" the barrel extension is m4 while the upper is definitely rifle but according to the pic with the 4 examples this should be "OK" though not optimal.
tried loading about 10 rounds in the 20 round brownells mag, but same scenario, when the round on the left is trying to load, the bullet tip ends up contacting the upper right below the barrel extension feed ramp.  So not sure what is happening yet.

If I put pressure on the mag to "tilt" it so the front is higher, then the left round loads just fine, so I am wondering if the lower could have an issue with where the mag is locking in or?.

I just got in, and have some other commitments and probably wont be back online till later tonight/tomorrow, so i will take pictures tomorrow when im free, showing the upper/barrel extension relationship, and anything else I can see to photo.
thinking of putting the upper on another lower and seeing how it feeds with the different mags, and plus any info you guys can offer

ok, just now had a few minutes, was busy last night and today with other things....
the mag releases fine/locks in fine and I did clean it after assembly to remove any excess 33ms assembly grease and any manufacturing leftovers in the barrel/barrel extension.
but I will clean it again, just to have a clean slate moving forward.

of course im not sure, but this is my 4th ar type, it doesn't seem to be an issue with the BCG etc, when it loads it will fire and eject flawlessly, it was just not "tilting" [for lack of a better term] the round and it was hitting just below the barrel extension feedramps and basically stopping.  I have the BCG decently wet with CLP when I first test them out.

now I couldn't get to the range to test any more, but in the garage I loaded a couple rounds in the mag and it cycled those just fine except for one of those big 40 round promag things I picked up at a gun show a long time ago, and the second ASC metal GI type mag had been loaded for a long time in my closet, and at first it wouldn't even pic up a round from it, but after I removed several rounds and pushed the follower up and down, then reloaded the rounds, it would load/eject those rounds with the charge handle.

and it did still hold the bolt open on the last few rounds fired when we put "forward" pressure on the mag and ran those last rounds out, but I will be testing that again with a couple mags loaded with one only just to verify the different mags are not the issue.....and here is a pic of the mag release button where the catch assembly threads into it:

Try diff mags and try screw in your mag catch one more turn.

I don't remember asc mags being the tits....so get a new usgi Al mag and give it a go.

THANKS, I will def try this, I planned on it this weekend as I wasn't going to be able to get to the range, but life kinda got in the way.....so im hoping for some shooting time next weekend and will get these mags cleaned and tested before Saturday,

thanks again

I can do that, screw in the mag catch assembly another turn, and yea I was leery of the ASC mags too......hell, I don't even remember picking these up, but I will disassemble and clean them and retest etc...and of course stalk the local spots looking for some usgi mags as well........

thanks again