Couple of months ago I gought a new Colt  SP1 upper, bolt, & BC from a forum member. Excellent deal, everything fine. Im using a preban SP2 lower, both are large pin. Problem is the SP1 upper won't feed and chamber reliably. Went out again yesterday with both. Ran fifty rounds of my reloads through the SP2 set up, was flawless. (55g fmj military pulled w/surplus 4895)Tried the same rounds/load in the SP1 and either it would not strip rounds off the nagazine completely or the bolt would not lock completely. Have tried different magazines. If I insert round in chamber and release bolt it locks up fine. Tried ten rounds of Winchester SP through the SP2, again, recoil ws a little harder but functioned fine. Tried ten through the SP1 upper, it functioned but not as smoothly as the SP2 upper. Have tried different Colt magazines. Suggestions?  Thanks

Rk

Quoted: it functioned but not as smoothly as the SP2 upper. Rk

can you elaborate on that a bit?

It just didn't feel right. Not as smooth. But then it could be that its new. The SP2 is like silk. Its a GS model and is an excellent shooter. I'm just wondering if the SP1 upper just has to be shot a lot more to smooth it out. Hell, I don't know.

rk