Hmmm...
Tough call....
I recently had a bad experience with 2 Bushmaster uppers...
A Pre-ban 11.5" HBAR w/ 5.5" pinned flash hider, and a Post-ban 14.5" HBAR w/pinned 1.5" AK brake...
The 11.5" barrel NEVER ran right...
It was sent back to BM, and still didn't work right...
I called BM & spoke to a 'smith, and he said the 11.5" guns either work, or they don't, and he said the gas systems are VERY fussy.
I asked him if I should send it back & swap it for a 16" barrel, and he said "That would probably be a good idea"
So instead, I traded the gun on a FAL...
The 14.5" upper gave me hell right away...
The chamber was WAY too tight, and shells were getting stuck in the chamber...
I sent it back to BM, and they "Polished" the chamber...
Got it back and it worked about 80% It was 'kinda fussy, and never ran 100%...
This gun got traded too...
The BEST Pre-ban upper I've tried was a 16" DPMS Flat-top with an M4 barrel and a birdcage flash hider...
This upper ran 100% right out of the box....
There was a NOTICEABLE difference in quality between the Bushmaster and DPMS barrels...
On both of the BM's barrel extensions, it looked like they were old, used, rusty parts that had been glassbeaded...
You could see the rust pit marks in the metal...
On the other hand, the DPMS barrel extension looked like it was brand new and highly polished...
VERY nice stuff...
I GUARANTEE YOU my next upper WILL be from DPMS !!!
P.S.- Stick with a 16" barrel, the gas curve is much better for cycling reliability...