Would you say it is crappy magazines? I'm shooting an LMT lower, BM 16" upper, LMT BCG, and SOPMOD stock. After I shoot a mag and put a new one and hit the bolt release, I'd day 75% of the time the round won't feed. What could be my problem?

Make sure you really slap the bottom of the mag!!! That extra push may be exactly what's needed...

My guess ... weak buffer spring.

It may be a combination of a tight mag (meaning bullets are packed in tight because of a full mag) and a weak buffer spring. Hence the bolt is unable to strip the top round off completely when the BC is released.

Note that it only happens with the first round. That is beacuse it is still tightly packed. Once that is stripped, then the other rounds are easier for the bolt to strip off.

IMO.

ETA: What mags are you using? Did you change followers or put in Magpul Ranger Plates? When fully loaded at 30 rounds. Does it still have "play" when you press the bullets down the mag?

Quoted: My guess ... weak buffer spring. It may be a combination of a tight mag (meaning bullets are packed in tight because of a full mag) and a weak buffer spring. Hence unable to strip the top round off completely. The reason it only happens with the first round is because once that is stripped, then the other rounds are not packed as tightly as the first and thus easier for the bolt to strip off. IMO.

Any recommendations on a better buffer spring?

+1 on the unseated mag.  Make sure you give it a good slap to ensure proper seating.  Also, tighten your mag catch a time or two.  I was having problems with this and tightening the mag catch solved the problem.  Try that before you drop coin on a new buffer spring.

Doc

Check out my additional comments first to be sure it's not just a mag problem.

If your answers are all "no" to the question of changes to aftermarket plates and followers AND "yes" to the play, then it may indeed be weak buffer springs. .....

In that case, lets wait for what the other members would recommend. I am from another country and do not know what are available there.

OR as they said - it may just simply be an unseated mag .... check that out too.