Hello I'm new here, anyway, I recently bought a Daniel Defense Big Hole Upper to use as a second upper on a Colt SP1. As soon as I got it in I removed the original upper and checked the DD for fit. It was a no-go. The rear hole was placed correctly and would allow the pin to lock but the front pin hole (Big Hole) was about 1/8" off center. There was no way it was going to fit. I put the rifle back together and re-packed the new part to ship back. I called the warranty dept. this morning several times...no answer, so I called tech support to try to speak to someone. I spoke with the guy and explained the problem and he responded "oh thats not too good." Well I got it shipped back and am asking for a refund. I hear a lot about how good DD products are but I'm not impressed. Seems to me they have a QC problem. That part should have never shipped. I waited a long time for those uppers to be restocked and when they finally were they were not made correctly. Oh well, I guess I'll just shoot the old Colt as is. If anybody else out there is thinking about buying one of these all I can say is don't waste your money.