I was thinking on buying a .45 upper. I no longer have any ars left but have had many in 223 and 1 in 9mm. The one I am looking at is an Olympic 16 in w/threaded barrel and comes with 3 mags,buffer, bolt etc. Any one have any feedback on reliability of these in .45? I plan on building a lower probly DPMS with a different trigger for it. Will the upper work on any lower or will I need different hammer like the 9mm.