As some of you may remember I wrote a few weeks ago about the trouble I was having with an upper receiver that I bought from Model 1 Sales. The rounds were getting stuck on the feed ramps. Well I sent it back to them and they said they polished the ramps and tried the upper on  Colt, Bushmaster, and Rock River lower and it worked perfectly. however when I got it back today and tried it, the rounds STILL get stuck, but only on the left side. I thought I saw a post a while back that was exactly the same thing. Can anyone point out the post and/or help me with this problem? I am at my wits end. is there ANYTHING I can do or should I send it back again and ask for a refund???

Quoted: If its only having probs with the rounds comming off the left side, check for burrs or lip prob on the mags, I had a couple do me that way. After stonning them a little they worked fine hope it helps

Do you think this will help? I have tried Sanchez, Center Industries, Colt, and Bushmaster. They all do the same thing.

Use the search feature.

Really check the left feed ramp. Since the right one works maybe they didn't do a very good job on the left feed ramp. Use a fine round file first then rubbing compound on a q-tip. Can make the ramp smoother than monkey s#!t. Just look at it real closely with a flashlight and operate the action real slow and see if you can pick up the problem.