308 Pistol/SBR

[airtoad]

Currently back overseas, but had an opportunity to get some rounds through my build and collect data while breaking in the barrel, adjusting the gas block, using the magneto speed, and sighting in the Nightforce. Initially was a little skeptical of the CMMG 12.5 barrel as I had read some conflicting reviews, but had no issues. I wanted to use factory ammo to get some baseline velocities with all weights before deciding on a good bullet for reloading for barrel length. In a nut shell I shot 110/125/130/150/165gr Nosler/Hornady and Barnes, all were surprisingly accurate. Sighting in at 25yds I got a normal ladder depending on bullet weight and all groups were under .5". Having set targets at 25/50/100/150/200 all behind one another I was able to see all my bullet drops and compare them to my magneto speed velocity and inputs to a ballistics program, all really close to my predicted velocities. The 110gr Hornady SST bullets have a factory velocity of 3500fps, based on a 15 shot avg over the magneto speed the 12.5" barrel produced 3240fps, I shot three round strings before cleaning the barrel and shot a dry bore At 150yds the 110gr bullet started to deviate from .75" and at 200yds was just barely over 2.5" I assume it's slowing pretty quickly and stability is an issue. Nosler 125gr and Barnes TTSX 130gr both with a stated factory velocity of about 3100fps were hovering around 2810fps and held a consistent .75" to 150yds and 1.5" at 200yds. The Hornady 150gr SST Super performance and Barnes TTSX state velocities were 3000fps and 2820fps respectivly the SST avg over the MS was 2730fps and the TTSX 2690fps great grouping at 200yds of 1.5" Hornady Super Performance inter bond 165gr (probably the heaviest I'll go)  Stated velocity 2840fps yielded a consistant 2580fps and grouped right there with the 150gr. 

I've got the Primary Arms CQB 30 on the muzzle and blast/noise isn't an issue, not an MP-5 SD but not a 12ga breachers shotgun either. I need to get out and do some testing at longer ranges +400yds, I'd expect the groups to remain in the 3" range out to 300yds, the 110gr bullets I'm sure will jump to around 5" looks like a good short range round? I was impressed by the consistency in velocity and I'm sure the shorter barrel contributed a bit to the accuracy. Not too shabby though for 12.5". 

Blackrain billet receivers 

POF BCG and Adjustable gas block

Maxim Defense stock/jpscs

CMMG 12.5" Barrel

Elftmann Trigger

Odin k-mod forend