"Best" is mostly a matter of opinion, but.....
Not long ago the answer would've been "Stick to the ABC's" (Armalite, Bushmaster, and Colt).
These days, with over 40 manufacturers making AR15's, M-4's, or simply lower receivers, it's very hard to say who makes "the best" AR anymore.
The "ABC's" are still a save bet, but many companies are cranking out exceptionally high quality AR's.
(Mark) LaRue makes an incredibly well-built receiver that's CNC machined out of solid 7075 aluminum. The trouble is - you have to pay a large premium,.. IF you can find one.
There are still Diamonds around (machined out of billet stainless steel). They're very precise, very strong, very expensive, and very hard to find though.
Someone else is still making a SS AR, but I can't remember who it is right now (DPMS maybe,.. not sure. I'll post when I find out).
JP Precision makes a complete AR now (made only precision replacement and competition parts until recently). Everything they make is top of the line stuff!
There are other high-end AR's out there (like MagPull), and the numbers are growing every day.
pof-USA hands down
From 2013-2015 it has been the AR15.
7.62x25 is the Tokarev pistol cartridge. No manufacturer currently makes an upper for that cartridge.
Try AR15.com Try AR15.com
If it is one of the recent Colt .22LR AR15 rifles, then the answer is no - they are completely different internally.
1959
Yes
The US Army presently uses the M4 carbine, a shorter and much modified version of the Armalite AR15.
Colt has not offered a AR15 in 308
By it's serial number. Go to www.proofhouse.com and under 'long rifles' listing look for AR15 Sporter
@ 40 inches.
Yes