Here is a pic showing 2 of the 3 builds I completed last week; M4 using Ameetec lower, BM A3 upper, BM 14.5" M4 barrel, BM lpk, Colt green lable bolt/carrier group and BM A2 stock; 11.5" Commando using 11.5" BM fluted HBar, older BM lower, BM A2 upper, BM lpk w/ M16 fcg, Colt M16 bolt/carrier, no-name carbine collapsable stock, & rdias. Both ran great this past Saturday, with 450 rounds through each at Pop Dean's Range. Both rifles knocked down bowling pins with regularity at 125 yards using white box Winchester 55gr ball ammo (Q3131).
Also recently completed 2 builds using Bushmaster lowers, but won't use them again, as the rear shelf is no longer mil spec height - a rdias won't fit without modification on the new lowers, and the fit/finish just isn't up to par with the new LMT lowers that are available from DSA.
In regards to a higher quality lower that is slightly more expensive, I'm picking up 2-3 of the new LMT lowers that are being marketed by DSA from my dealer this week and would strongly suggest the same for anyone attempting a build who is looking for the highest quality lower available.
They are reported to be of excellent quality, as one would expect of LMT. I'll report back in the AR15 Discussion Forums when I pick them up and again when the builds are complete (have 3 lpk's on the way from BM - they should be here tomorrow).
Since you asked, there have been reported problems with both Stag and recently manufactured Mega lowers - although I used a Mega lower last summer for a build that went ok. The AR15 Discussion Forums have reported that there may be a problem with the mag wells in the newer MEGA lowers and possible problems with a few MEGA & Stag lowers regarding flaking of the finish.
Personally, I would suggest a qualtiy lpk and like BM. Many have had good luck with DPMS - a search on lpk's is advised before you spend your hard earned money and suffer a migraine if modification of any of the lpk's piecies are needed when attempting your build.
I believe that choosing high quality parts is the key to success in a trouble free build.
I ran across this discussion on the FAL Files regarding AR15 lower receivers just a few minutes ago that has some nice pics & infor and felt it pertinent to include:
AR15 Build DiscussionBest of luck on your efforts,
Clay