300BLK Range Report

flashpan · Apr 11, 2020

I posted this in a rifle build thread but thought it better in ammo/reloading.

Well I promised to share a 300BLK range report ... this could put some folks to sleep but here goes.
The goal: Develop a handload for only subsonic, suppressed with accuracy of 2 MOA for AR pistol with low cost bullets. No intention of hunting except night coyotes so energy is not important...soft recoil and quiet are priorities.
The pistol: Home built side charge upper, Andersen lower, 71/2" 1:8, SBA3, primary arms 1-6 scope. photo
Testing: April 9, TCGC, 65d, 5mph, all 50 yrds, all suppressed, Magneto Speed 3 chronograph. All 4 shot groups.
6 loads tested...3 handloads, 3 factory loads. Handloads = Fed brass, CCI 450, AA1680 Velocity and Accuracy Results:
I hesitate to share actual charge data!!! PLEASE BE CAREFUL. Loading 300BLK is not like most cartridges...most folks work charges down to a load that functions well...TOO LOW you can stick a bullet in your barrel. DOUBLE CHARGE like a pistol cartridge...disaster!

Round	Bullet	Load	Ave Vel	Accuracy
Handload	208 Amax	11/1680	1033	.46 wow photo
Handload	208 Amax	11.5/1680	1096	.96
Handload	200 Accubond 2nd	11/1680	998	1.9 kehole? photo
Handload	200 Accubond 2nd	11.5/1680	1044	1.2
Handload	200 Berrys Plated	11/1680	874	3.9
Handload	200 Berrys Plated	11.5/1680	934	not measured, poor
Remington	220 FB	Factory	845	3.5"
Herters	200 Open Tip	Factory	1001	.560 wow
Sig	220 Pointed	Factory	997	1.3 3 touch

Notes, Observations, Results

Testing was time consuming but went well after fitting and adj sensitivity on chronograph (on suppressor)
All loads functioned well, all shot single shot, bolt lock back on all. Seems maybe overgassed, dirty brass as expected, ejecting to 2 o'clock, but with side charging bolt not sure what that means.
Several handloads obviously went supersonic...a bit surprised at high velocity from this 7 1/2" barrel.
Clearly the Amax load exceeds accuracy hopes, will cut back the charge. 1000 fps is prefered. photo
Do not understand, but looks like accubonds keyhole? Bearing surface could be too long for barrels 1:8 twist?
Berrys test confirms previous testing with coated and plated bullets, this barrel hates them...I give up after testing 4 diff bullets and two powders. I have shotguns that pattern better. And flaring case mouths and recrimping is a PITA anyway.
Remington factory velocity surprisingly low...tested before...high ES and SD ...wont group
Herters WOW ... who knew...maybe forget all this reloading stuff and buy this ammo.

Summary: I am happy with the build and now very close to a go to load with 208 AMAX at 1000 fps. Pleasantly surprised at how well this generic short barrel shoots these jacketed bullets. Rather not try another barrel to find accuracy with coated or plated...not sure anyone has found 2-3 MOA with costed/plated. Missed one goal for a low cost bullet.
I hope someone finds this useful. I got hooked on 300BLK this first time I shot a suppressed round. I'll put the finishing touches on the AMAX load and go find the first coyote ... maybe in the country near you? But you will never hear it.

RainMan_PNW · Apr 12, 2020

Nice. Any concerns with long term availability since Hornady has discontinued the 208 AMax?
I'm looking at trying to work something up with their Sub-X pills using the powder samples you are sending my way.

flashpan · Apr 12, 2020

Good catch...yes it figures a discontinued bullet is the one. It started when I bought some factory ammo with the 208 AMAX...shot pretty well, then pulled some of the bullets, handloaded and great results. Well I have a line on about 400-600...just waiting for a price. If I run out, I may try ELD's and would consider the Sub X for sure. What are you going to try? We can trade bullets for testing if you like.
The powder will be on the porch tomorrow...Enough to load 50 rounds of each powder.

DizzyJ · Apr 13, 2020

Thanks for the writeup! Sounds like you've got a couple of winning combinations there!

flashpan · Apr 13, 2020

Thank You
I did score 300 of the 208 Amax bullets on Accurate Shooter. If someone wants to try/test them, give me a shout.

John Gault · Apr 13, 2020

I'm having really good luck with the Hornady 208 grain JHPs in my Blackout..
Expensive to shoot vs 223 but that sound ..
Also looking for another backup bullet. Was hoping Berrys would be it...
Maybe not..

flashpan · Apr 14, 2020

Yes...I paid 30 cents for the 208's I found...a decent price on a discontinued bullet, but still expensive.
Berrys will send you sample packs in case you did not know...for 200 and 220 grn. I really did not give the Berrys 200grn a fair shake, only tried the one powder, one seating depth.
Have Fun!

osprey · Apr 14, 2020

If you are ejecting at 2 o'clock with suppressor on you are probably fine on gas. Side charging bolt has no impact on it and should work just as a non side charging bolt. That is odd the accubonds keyholed, were they the lr version? I would encourage you to test all new loads without suppressor to check for stability first. This will prevent possible baffle strikes. It looks like you found some good combos to work with, nice job!

flashpan · Apr 14, 2020

Thanks Osprey ... I was not sure about ejection being the same. The noslers were not LR, they were 2nd's and the worst seconds I ever saw. Tips gone or bent, bad surface blemishes. I only loaded ones that looked good. Not sure how it affected accuracy. Glad my suppressor survived it!

flashpan · Apr 27, 2020

Ran one more test before starting some volume loading. Did not add this to the first post yet. Lowered the 1680 charge in search vel right at 1000fps.

10.5grns ave 1,001
10.7grns ave 1,014

Guess I'm done. She is soft and quiet now!!

osprey · Apr 27, 2020

Interesting, I had to go to 11.7 grs of 1680 to get 1000fps out of my 9" blackout with 208 amax. Different lot of powder, slight case capacity differences, different seating depth, who knows but shows why you never take someone else's load data as the gospel.