After what seemed like forever I finaly got my gun today. It is a Bushmaster 16", phantom supresor, A3, M4. I put the Aimpoint Comp ML XD with a carry handle mount. I love it. I shot 40 rds of winchester Q3131. The first 20 went great. The second 20 started to not feed. It looked like the bolt was not coming back far enough to let the next round come up all the way. Has this happened to anyone else and if so what is the fix. Could it be the ammo. I also used 2 different mags. or does it just need to be fired more to break it in? Also I would like to thank everyone on this board for the help on questions. It made a great differance to me for my purchase.

Congrats!  [beer]

d....3  Sounds just what I went through with my bushmaster.   I got rid of the ten round mag for one.   I then clean the gun and got rids of the factory oils and lubes.  I clean with a good CLP cleaner and used a law Enforcement stamp 30 Rd Mag. Shots like a dream. I was not to sure of the gun at first tell I cleaned it and fired about 500 rounds through it.  I can't wait for sunny days to shot it now.   Now if I could get used to the AK Brake.  Damn its loud but I guess thats why they make ear plugs.

When I had to wait for the Feds to approve the sale to me they never did answer so as to the law it was mine,
 No problems though , mines a colt.
 Good luck I'd take it back ASAP.

Congrats on your purchase.  I have the 16 inch A3 Bushy and love it. [beer]  

As for the malfunctions.  Did you breakdown the gun clean and lube it before firing.  Also, were the magazines the same brand? I recently learned a lesson on cheap USA Brand Mags and experienced similar problems to what you described.  It seemed that the rounds were being ridden over and not stripped from the mag or I had the opposite with the round popping up into the receiver when it was in full recoil.  Turned out to be the mags in both cases.  I think it might be more likely that your bolt is going all the way back but stops as it rides on the round.  Are there any creases in the rounds made from the bolt?  

Make sure you clean it and try some Thermolds, Orlites or USGI's.

Clean it reall good . Bolt and all. Probably has alot of thick packing oil on it.

The AR-15 is a fun gun, Kind of like a grown up .22.
It does require good maintenance however. I spend more time cleaning and lubing it than any other firearm I have. (Although the M1A ia a close second)
[sniper]

Congratulations on your Bushy. [^] [^]
My transfer agent called late yesterday afternoon to tell me that the 2 Bushmaster A3 carbines my brother and I ordered came in. We're going over this evening for the paperwork. Should be able to pick them up Friday night. IN TIME FOR THE WEEKEND!
I'm soooooo excited! [:D]

[beer] [beer]

Congratulations!!!  I remember the exhilarating experience of buying my AR-15.... ah the memories.... I’m going to go and fondle it after I send this message. [:)]

Make sure that it is Q3131[b]A[/b] ammo (note the A).  The Q3131 may be from a bad lot that caused the problems you described.  When I first got my 20" Bushmaster, I put 200 rounds of Winchester Q3131 (not Q3131A) through it.  I was very disappointed.  It was having the same problem you describe.

The fix:
1) LUBRICATE the gun.  It's new and needs to be especially slippery until it breaks in.

2) Try different ammo.

3) Use USGI or US made Thermold magazines.  My factory magazine worked ok, but stay away from after market brands like USA.

I forgot to say that the mags are 30 round and apear to be the same mfg as the one 30 rounder that came with it. (they have the bushmaster snake on them and are stamped metal) I did not clean it before I shot it. My bad. I couldn't wait. I cleaned it realy good when I got home and found that the oil that was in it looked thick so that may have been the problem. I also learned that I need to have my ear plugs with me when I shoot. I was so excited that I didn't take any of my range stuff with me. I still cant hardly hear anything. I guess that's what happens when you get a new member in the family.[:D]

Your problem may be a loose gas key.  This is the little tubey thing bolted to the top of the bolt carrier.  My Armalite's got loose and I had exactly the same prob . . . it was a 850$ single shot.  Just torque it down to 35-40 inch/pounds and restake or loctite. Ditto to everyone on lubrication.  The AR is NOT meant to be run almost dry.  Some CLP/Tetra/(insert your favorite lube) on the bolt carrier may help.  When I first got my AR my only experience was with AK's . . . I had lots of problems until a wise AR15.com member reminded me to use more lube than I did on my AK's.  Since then, the only probs I have had have been due to blown primers in Spanish SS109 ammo - now that's a pain in the a$$!!

Ballsy

Thanks for the reminder, guys.  I'll be sure to clean and lube my Dissipator and new V-MATCH upper BEFORE I go to the range.
And, I can't wait to try those "most favored" USA brand magazines I put green followers in...
Got some USGI 30's to try, too.  Then there's the Pro-Mag 20's.  And, the Eagle-30 polymers, and that outrageous 120-rd. Chinese drum.  TESTING will be fun, to say the least.   I wonder if a green follower will fit the drum?  HA!