I just received an upper from a guy on the boards. RRA 16in A2 preban type. I put it on a RRA lower I have with 200 rounds fired. Has worked great with no problems with a bushy upper(not one problem). The mag was a almost new Parsons 30 round that has worked 100% in three other rifles. I fired one round with the newer upper and got a partial feed. The fired case ejected but the bolt caught the next round about half way in. Oh yes, the ammo was  ball from Ga. xxxxx over in Villa Rica. What do you guys suggest my fix is??????????? The stock is a RRA 6-pos.

Put it back on the bushy.

Is there any resistance when you work the charging handle? Any burrs on the carrier?

I'm guessing it is the magazine.

If the new upper has a carrier with the milled out ramp I would check the firing pin collar size and the hammer in the lower for proper clearence.

WOW....I see there's alot that can go wrong with these. Believe it or not I have owned  six of these and never had any problems with any of them. Of course except for a Colt SP1 I had back in the late 70's, I haven't fired more than 200 rounds thru any of them. This upper I just bought did not come with a b/bc/ch ,so I used the newest one I had (RRA). I bought the b/bc/ch for the bushy about six months ago. If any of you have noticed the EE I have sold three of them in the last 7 or 8 months. Armalite, RRA varmint and RRA 16in SS A2. I thank each of YOU for your help and will start checking out each of your suggestions in the morning.

What everyone else said.  Let us know.

If your mags don't number in the triple digits, your collection is severely lacking.

 I will have to go count and see if I am even in the double digits.

Quoted: Check your carrier key.  Make sure it is not loose.(nope) Check the gas tube and make sure it is pinned in place.(not sure what you mean, but not loose) Check to see if the gas tube is rubbing on the carrier key at all.(nope) Put one round in the magazine and fire the rifle.  Does the bolt hold back?(yeap) Is the upper cleaned and lubbed correctly?(yeap) Have you tried other ammo?(nope) What kind of buffer are you using?  Just curious.(came in new RRA 6-pos) Have you tried a different magazine?  I read what you wrote, but it wouldn't hurt to try.  And don't give me any crap about not having more magazines.  If your mags don't number in the triple digits, your collection is severely lacking.  [:D](well low and behold....worked great with another mag. Or a least for three straight rounds..boom.boom.boom. I felt like 5 rounds total was about all my neighborhood would stand at 8:00am) Looks like that one mag will work in everthing else but not this one.  Go figure!!! I own 8 Parsons,2 Centers and 1 unknown MAGS. Thanks for all the input . I'll know better whats going on as soon as I can find time to go to Redlands.

Quoted: WOW....I see there's alot that can go wrong with these. Believe it or not I have owned  six of these and never had any problems with any of them. Of course except for a Colt SP1 I had back in the late 70's, I haven't fired more than 200 rounds thru any of them. This upper I just bought did not come with a b/bc/ch ,so I used the newest one I had (RRA). I bought the b/bc/ch for the bushy about six months ago. If any of you have noticed the EE I have sold three of them in the last 7 or 8 months. Armalite, RRA varmint and RRA 16in SS A2. I thank each of YOU for your help and will start checking out each of your suggestions in the morning.hr

I seem to recall something about that he

I'm glad that you are enjoying your AR....I might have been better off keeping it. The upper I bought will be ok, I think. I just paniced when it  jamed  after every shot. I can't believe that the mag I was using had worked in everyother rifle I used it in. YOU can tell from the AR I sold you that it was not used much and that I was careful with it.
ANYWAY, enjoy and keep safe.(moleman)