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Breaking in the 300 BLK


shibiwan

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Took it to the range today for the virgin shoot.

 

Tried to shoot a mag of a buddy's reloads (220gr subs) and performance was inconsistent. Short cycling.

 

Switched to Rem UMC 220gr subs and it was better but still hiccups. The bolt carrier is on the tight side in the upper receiver bore. I figure it will take some breaking in..... still, I had expected more stoppages when firing subs unsuppressed.

 

....and then while cleaning the barrel between rounds, got the stupid OTIS patch+ eyelet stuck in the $!$@#%$@% chamber and couldn't push it out with the obstruction remover. So much for breaking it in. 20+ rounds and it's stuck in there. Good news is it popped right out when I got home and used my conventional cleaning rod.

 

Overall, pretty happy. Recoil is like a peashooter. This is gonna be fun when I get the bugs worked out.

 

Back to the range on Sunday then.

Edited by shibiwan
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Part Two

Finished up the rest of the 300AAC subs I had, a little over 100 rounds. Hiccups worked themselves out after the 1st mag today, kept everything oiled and everything ran like clockwork (except the 20 rounds of crappy reloads from my buddy). I think there's something to be said about using the pistol length gas system that allowed it to fire subs unsuppressed using the 14.5" barrel.

 

Pretty happy with the MAS Defense barrel for what I paid for it; groupings were tight and consistent (averaging around 1.5" at 100 yds). This is probably the easiest gun that I've shot ever.

 

Next

time for my own reloads. Scored some 208gr A-Max yesterday at sportsman's. Gonna see how they do with the recommended AA1680 powder..... I so need to get a chrono.

 

-S

Edited by shibiwan
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Sounds like youve got a fun little toy there, congratulations.  That sucks with the otis eyelet! Ive never really liked the idea of a  cable or boresnake setup and now I really wont try them after hearing that.   Are you running an adj gas block?

 

I love the otis cable... wish we had them while I was in the military. Makes cleaning a breeze, especially when breaking in. You don't need to takedown the rifle, pull the BCG etc, to insert the cable and simply pull straight through between shots. This is the first time I got my eyelet caught... never seen it before so I assume it was a freak occurrence.

 

The beauty of the 300 AAC Blackout system is the rifle fires both subs and supers equally well WITHOUT the need to adjust the gas flow, so no adjustable gas block is needed, suppressed OR unsuppressed. :D

 

The research I did before I started on the project showed other shooters had various different results with the 300 AAC, most of them was the inability to cycle subsonic rounds when unsuppressed. Since that is the "most problematic" conditions for the rifle to shoot reliably, I set that as my goal in this build.  I believe the magic is finding the right combination of gas tube length, barrel length, BCG, buffer weight, and buffer spring rate. Right now my formula is:

 

- 14.5" Barrel

- Pistol-length gas system

- 0.098" 0.075" gas port

- Cheapie BCG from PSA

- Std carbine spring

- Std weight buffer

 

I spent a lot of time to make sure everything was assembled correctly and smoothly before the first shots were taken. Seeing that the charge in the AAC is limited, especially on subs, I wanted to make sure there was minimal resistance in the action and maximize the energy from the gas return to cycle properly.

 

Upcoming Part Three: CNC'ing my own lower for the 300 AAC upper and maybe a suppressor while I'm at it.

Edited by shibiwan
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I could technically do it off the radar. Mostly it's paperwork.

 

Still waiting on my FFL (07) but once I have that in hand I have to pay the SOT-2 tax and I'm good to go to make them. Technically I will be able to shoot them under manufacturer testing but I can't own one until I get my NFA stamp, so it'll belong to the shop as "inventory".

Edited by shibiwan
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How do you like that MFT minimalist stock? I'm thinking about one of those for my wife's patrol rifle.

Her rifle is going to break me.

 

I picked that up because of the price and the unique look. The UBR (FDE) is on the way too. Just realized I'm an idiot and wasted money on the Troy PGRSA because I don't think it fits with the UBR. Anyway, it fits well, but a hair loose (not as loose as a standard carbine stock). Perhaps I'm being too picky for $49.99. Like how the rifle feels more compact, and how it could double up as a walking stick if I hold it with the "L" end of the rifle in my hand.

 

Going to strip the anodizing on the upper/lower tomorrow before either painting it or cerakoting it (stupid friend is lagging on the cerakote oven)

Edited by shibiwan
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  • 2 weeks later...

Part Two

Finished up the rest of the 300AAC subs I had, a little over 100 rounds. Hiccups worked themselves out after the 1st mag today, kept everything oiled and everything ran like clockwork (except the 20 rounds of crappy reloads from my buddy). I think there's something to be said about using the pistol length gas system that allowed it to fire subs unsuppressed using the 14.5" barrel.

 

Pretty happy with the MAS Defense barrel for what I paid for it; groupings were tight and consistent (averaging around 1.5" at 100 yds). This is probably the easiest gun that I've shot ever.

 

Next

time for my own reloads. Scored some 208gr A-Max yesterday at sportsman's. Gonna see how they do with the recommended AA1680 powder..... I so need to get a chrono.

 

-S

(Tom posting)  Brother, you haven't been listening to me from the beginning.  Here's what's to be said for pistol gas and subs, unsuppressed:

post-14435-0-35680200-1396239864_thumb.j

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