Say that fast three times...
Anyways I was in the shoot house today and had my bushmaster fail to feed, I swapped a fellow shooter for his bushmaster BC assy and it failed in his weapon too. Swapped out, Bolts extractors ect. Finally I changed to a old chrome Colt bolt carrier and it functioned flawlessly, anyone have this problem any other Ideas? Should I send the BC back to Bushmaster? HELP

You put your bc in his rifle & it gave the same problem? And/or vice versa? I would've bet on the mag giving the failure to feed prob.

You didn't mention the type of failure you were having, but this sin't the first Bushy BC failure I have heard about here...so, I will just tell you my experience(BTW, I'm hammered so I hope this makes sense).  I had a new Bushy M4 pre ban upper on a Bushy preban lower.  The first time I took the gun out it failed to eject about every 15 rounds.  Specifically, the gun was short stroking.  I figured this was happening because the upper assembly was new and had to brake in.  The next time I shot it, it choked on every round.  Essentially, it was a straight pull bolt gun.  When I stripped it, I noticed the gas key was loose, so the gas pressure was escaping from the area where the gas key meets the bolt carrier.  I guess what I'm trying to say is, check the gas key to see if it is loose.  Wow, all that typing just for the second to last sentence...

Make sure the gas key is STAKED not just screwed in really tight. I replaced the gas key on an AR once when the screws, after working loose, sheared off.

My neighbor had 2 Bushmaster carriers that had to sent back to the factory. He was getting very frustrated. He purchased them both as complete units for guns that he was building. Bushmaster checked them and sent him new ones. We used a bolt carrier from one of my Bushmasters and both his weapons functioned perfectly, that is when he decided to contact Bushmaster and have them checked. Bushmaster gave him good service.

Yes it seems to short stroke. The fired cases barely roll out, and it fails to pick up another round from the Mag. We tried several Mags that we knew were battle worthy. The only thing I could come up with was a bad BC, I am glad (I Guess) to hear this has been a problem with Bushmaster BCs. Does anyone know if Busmaster marks thier bolts MPC like Colt does?

I have to go with Imbroglio, it sounds as if the key could be loose.

Bushmaster seems notorious for not staking the carrier key.  I got a 11.5 complete upper from them for my registered full auto Colt 614 and had the same problem with a loose carrier key.  They also seem to undersize the gas port.  After staking the carrier key and opening up the gas port, mine runs 100% now.

Last Saturday, I went to the range with a buddy from work.  He had just gotten his son a Bushmaster.  He had a similar problem.  He would chamber the first round then fire it and then it would not chamber the next round.  He was using South African PMP .223.  We tried 10rd, 20rd and 30rd mags with the same result.  PMC and USA ammo produced the same result.  The range traded him Winchester .223 for his PMP .223 and then he had no problems.  Meanwhile my Colt Sporter II and Match Hbar had no problems with any of the ammo.  He decided to give the PMP another shot and had the same problem. Any ideas on this one?

Do you have a chrono available to chrono the ammunition?

If the PMP is significantly slower than the other ammo, it may be that there is a gas leak somewhere in the gas system (or the gas port is undersized) and there is not enough gas getting into the system at high enough pressure to run the gun.  Other, slightly hotter ammo's are getting over the threshold.

I'd check the bolt carrier parts first since they are the easiest to get at and check.  Make sure the gas key is firmly in place and the gas rings on the bolt properly misaligned with one another (not that that should be a show stopper).  IF all seems to be well there, you may want an AR armorer to gauge the gas port and see if it is in spec. If not, have it fixed.

ANother Bushmaster problem I've heard tell of is  them installing the wrong buffer springs, especially in CAR buttstocks.  THe buffer assembly in the CAR buttstocks is shorter, including the spring.  IF a full length AR15A2 spring is substituted for the proper length CAR spring, you could get too much resistance to the rearward motion of the buffer and bolt group causing extraction and ejection problems. Possibly just enough over-resistance to inhibit only some, slightly lower powered ammo to properly cycle.

A rough chamber might also grab softer brass more easily and slightly slow extraction and ejection, but you'd probably see some evidence (new wear/abrasion on the cases)

Oversized brass might also cause troubles. Using a cartridge /case gauge to see if the PMP brass is significantly larger/tighter in the chamber than the other brands could be revealing.

so many potential problem spots....

I had a BFI come with a loose carrier key as well.  Bushmaster says to tighten the screws to 35 to 40 inch lbs. and stake them.  Armalite says to tighten them to 55 to 60 inch pounds and stake them.  

Also look at your gas rings to be sure that the slots are staggered.  If even two adjoining rings have the slots close to being aligned you will notice a drop in pressure / reliability.  I have just recently installed an Armalite "continuous coil"gas ring in my M4.  It is one piece and there are no gaps to space. I only ran about 150 rounds on it but it seemed to smooth the cycling out a bit.  

Also as long as you are at it, check the gas tube where it goes into the front site post.  Sometimes they crack where the roll pin goes through and some gas escapes from the system.

Good luck,
Mario