Finally got around to staring my load development for my little suppressed 300 shorty. Has an 8 inch barrel. Started with a plethora of mixed cases. Sized and deprimed, trimmed all to 2.355-2.360. Pried them up and loaded a test run with 8.0 grains H108, they wouldn’t quite cycle the bolt, bumped the charge up to 8.8 grains and we are in the money now. Bolt cycles and locks, suppressed or not, and they are going down range at what I think is about 1000-1050 FPS I’ll verify this on another day. It’s like standing in a sauna here today. 100% humidity, you can see the steam in the air, anyway. I shot a test batch of 25 rounds this afternoon 10 for function and 15 for accuracy tests. A beer can at 20 yards is child’s play free handed.
So the rifle is a built by me 300 blackout, it is stamped as an SBR and the suppressor is also stamped, but due to my own judgement I won’t post a pic of it. It is built off of a Anderson lower and upper it has a magpul grip and stock, the lower has a 3.5 pound CMC trigger in it which actually breaks at 3. It has a Aero precision hand surf and I went with an 8” CMMG barrel pistol length gas system of course. The bolt carrier group is a spikes tactical. It is topped off with a bushnell red dot and a set of magpul flip up irons and an inforce 800 lumen light. The suppressor is a silencerco hybrid, used as a direct thread. It is an armadillo eradicating machine.
The load worked out to this.
Case: mixed
primer: Win SR
Powder: H108 surplus
Bullet: Lee 309-230 powder coated and sized to .309
Charge weight 8.8gr.
COAL 2.200-2.210 probably powder thickness on nose for the variation.
The H108 is some of the best metering powder I have ever used. They drop from 8.0-8.08 in the Honrnady AP.
I was on a nit so stable rest and the sun has fell to my front and I lost my cheek weld on the left group. The right group I believe the flyer was the 5th round off the follower of the mag. I have noticed the last round in the mag always has a different point of impact out of any AR style rifle I have. Guess it’s the difference in the drag of the follower in the mag than a brass case.
All in all I am happy with the load, going to load 225 five or take more and we will see what they do at 50 yards.
So the rifle is a built by me 300 blackout, it is stamped as an SBR and the suppressor is also stamped, but due to my own judgement I won’t post a pic of it. It is built off of a Anderson lower and upper it has a magpul grip and stock, the lower has a 3.5 pound CMC trigger in it which actually breaks at 3. It has a Aero precision hand surf and I went with an 8” CMMG barrel pistol length gas system of course. The bolt carrier group is a spikes tactical. It is topped off with a bushnell red dot and a set of magpul flip up irons and an inforce 800 lumen light. The suppressor is a silencerco hybrid, used as a direct thread. It is an armadillo eradicating machine.
The load worked out to this.
Case: mixed
primer: Win SR
Powder: H108 surplus
Bullet: Lee 309-230 powder coated and sized to .309
Charge weight 8.8gr.
COAL 2.200-2.210 probably powder thickness on nose for the variation.
The H108 is some of the best metering powder I have ever used. They drop from 8.0-8.08 in the Honrnady AP.
I was on a nit so stable rest and the sun has fell to my front and I lost my cheek weld on the left group. The right group I believe the flyer was the 5th round off the follower of the mag. I have noticed the last round in the mag always has a different point of impact out of any AR style rifle I have. Guess it’s the difference in the drag of the follower in the mag than a brass case.
All in all I am happy with the load, going to load 225 five or take more and we will see what they do at 50 yards.
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