I've been using that setup for well over a year now.
I'm running a factory stock 20" HBAR upper from my postban Bushmaster XM15E2S, on a preban Eagle Arms lower with collapsible Fiberlite stock, and carbine H-Buffer and spring. (New York AWB compliant of course
The 20" hbar barrel has a 1/9 twist, A2 front sight base, no compensator, flash suppressor, or bayo lug. The upper is a factory assembled Bushmaster unit taken off a compelte rifle that I purchsed new in late '00. No add ons, or mods were done.
There were absolutely zero malfunctions to report while using this setup. Shooting details
In the last year, I have taken this weapon to the range six times and averaged 200 rounds per outing.
We fired this AR15 in all stages of fire, from very slow, deliberate fire, to controlled rapid fire with magazine change drills, and some all out heavy fire with the intent to lay down as much firepower on a target as the weapon could manage. Lot's of good hearty shooting!Ammo and magazine details
Throughout the year I used over a case of ammo, and a mixed group of 20 USGI magazines, all 30 rounders;
Ammo used was mainly Federal XM193, 55gr; 1,000 rounds fired. Various lots. I shoot this ammo almost exclusively through my AR15's because it is the most reliable ammo I have found.
Throw in 5 -6 boxes, 100-120 rounds of Tracer ammo from Talon mfg. Used on the occasional low light firing conditions. Mixed with XM193, 4-1 ratio with 3 tracers on the bottom of magazine. A nice visual for the spectators an other shooters.
Also fired were 80-100 rounds of USGI Lake City M855, 62gr. Green tip, military surplus ammo. These were already loaded on strippers and came in pocketed bandoleers. Nice ammo but that was the last of my supply.
The USGI magazines were from FN, Okay, Adventure Line, and Colt; All were
Ten magazines had new springs intalled along with green anti-tilt followers from a magazine refurb kit.
Ten magazines kept thier original black followers and springs... Kit was only good for ten mags.
Everyone who fired this setup was pleased with it's performance. The weapon was completely flawless in function, but I would like to see some minor adjustments that would make this setup even better.
First I would want to see an A2 style Flash suppresor/Comp on the barrel of this setup.
A flat-top upper would also be a great choice for this setup.
I think a M16A2 style barrel, turned down under the handguards, would be the best for this combo. The HBAR feels a little too nose heavy/front heavy for the setup, especially when firing offhand on a homemade tactical course.
After 1K+ rounds downrange you will get used to any weapon, but there was a definite room for improvement over the HBAR.
The balance and feel would be greatly improved with the lighter USGI barrel replacing the HBAR.
I hope this helps answer your question.