You're going to have a hard time getting a good suggestion when the problem description is "not good results". Honestly, other than possibly the fixturing of the upper, this is not a really firearm specific operation so I'd suggest asking in the general section to get a broader input potential. You are popping a 1" hole 8" or so deep in xxxx material. And describe the problem/results in detail or everyone will be shooting in the dark as they are here. I probably couldn't answer your question even if I had all the facts but I know enough to know there isn't enough information here to make any kind of targeted suggestion.