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???