Originally posted by Raptor937:
Come on throw in a range report

MG don't mind me asking, is it possible to use a 9mm heavy buffer spring for shooting 5.56mm?
Any 9mm builds?
Huh? Range report? What's there to report? I pulled the trigger, the rifle went BANG, the bullet hit the paper, I was happy!

Okay, here's a brief RR:
Since this was a new rifle, I needed to perform that wretched "barrel break-in" routine (shoot 10 rounds, pausing between each shot to clean the bore, then shoot 100 rounds, pausing every 10 rounds to clean the bore). I was shooting my tried-and-tested 55 gr. handloads that I normally use in my ARs with 1-in-9 twist barrels (my 24" varmint AR has a 1-in-8" twist barrel, and gets fed a different diet of handloads).
I also managed to zero the regular iron sights during the break-in. Very little windage correction was needed on the rear sight, indicating that the barrel was indexed correctly into the upper receiver, with no inadvertent offset to tilt the front sight base. Some other ARs, particulary the Bushmasters, have their barrels overtorqued into the upper receiver at the factory, resulting in a tilted front sight base and requiring massive amounts of left windage correction in the rear sight to properly zero.
No misfeeds or jams were encountered during the break-in, and the rifle was consistently holding sub-4" groups at 100 yards with the iron sights towards the end of the break-in. I was initially worried that the modifications I made to lighten the trigger pull of the 2-stage match trigger might cause the rifle to "double" or even go full auto, but that didn't happen.
After the break-in, I mounted the red dot sight and zeroed it. It's a cheap unit and I consider it disposable, but it held its zero surprisingly well through repeated double and triple taps. I planning on replacing it with a Hakko TacPoint red dot sight eventually.
A heavier buffer spring has the effect of mitigating the
felt recoil somewhat, but can potentially lead to misfeeds if it prevents the bolt carrier from cycling completely, especially if a cartridge with less-than-normal powder is encountered.
Using a heavier buffer (not spring) like the H-buffer intended for the 9mm version also has the effect of mitigating felt recoil
and reducing the cyclic rate in full-auto fire.
MG