here's what i can tell you from my experience....i own a G3 style rifle with a Freedom Arms reciever (i don't know who made the guts for it). keeping in mind that this is a carbine style with a brake on the end of it (the barrel is approx 16"-18" long) i get roughly 4 to 5 MOA with it. i haven't been able to do an extreme amount of testing with it, but so far machine gun ammo (which is 147gr FMJBT) grouped the best (closer to 2.5 MOA). other ammo that i've tried so far only included the heavier bullet weights, so i'm not sure how well she'd do with lighter weight hunting bullets. i had an issue with the sights on mine (ran out of elevation adjustment) so i removed the rear sight and put a scope on the integral rail. the brake makes it louder than a sunofagun, but all in all its a fun rifle. something to take to the range and blow some rounds off. definitely not a 300 yard deer rifle. as far as reliability goes, i have had a failure to fire a couple of times. these appeared to have been struck by the firing pin, but didn't go off. it was cheap surplus ammo, and it was only during one session in particular, so i'm guessing that it is the culprit. other than that i haven't had any problems with it other than the brass hitting the guys shooting between me and the far right lane. it tosses them WAY out there.
How the HK91 shoots I don't know much about. But one of the military G3s I've been issued with in the past shot around 2-2,5MOA with 146gr NATO ammo. That was probably the exception, though...as the majority of these rifles make more commotion than the average train.
All I know about the HK91s is that they're A LOT tighter than our G3s.. and in theory, you should be able to get sub 2MOA out of them with the right ammo.
Keep in mind that many G-3's were slapped together for infantry line troops and werent made with the highest regard. Now, H&K-91's in .308 shoot pretty dang good even in the short barreled variant. From what i know and remember, the H&K-91's i have fired allways out shot G-3's i have fired. However, the G-3's i have fired were normally old worn out rifles not worthy of accuracy testing.
Holy crap, 1.5-4 MOA, what the hell?? :roll: I shot a G3 already but didnt really pay attention to groups as me and a man I shot with every now and then were letting lose with one at full auto at 75 yards on an old oil drum. These HK rifles are kinda pricey and I would think they could bang out some better groups then that. Whats the deal on why they shoot soo poorly??