300 Blackout Subsonic Results and Questions

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n2omike

n2omike

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Decided to try the 300 Blackout, so I got a 10.5" PSA 300 BO upper to try on my 5.56 AR 15.

I tested with Winchester 296 (H110) and Berry's 220 Copper Plated bullets.

I loaded up 9.5, 10.0, 10.5, 11.0, 11.5 and 12.0 grain loads all at 2.150" overall length and took the chrono with me to find a good subsonic powder charge.

First trip to the range, about 10 seconds after turning the chrono on, the display said 'BAT', which means 'dead battery'. Great. lol I went ahead and shot few each of 9.5 to 10.5 and didn't hear any sonic booms... then went home to get a new battery.

The lower powder charges were very inconsistent. Total range of velocity was close to 100 fps. At 10.5 grains it ranged from around 1040 to 1150, with one going supersonic. The higher the charge weight, the more consistent things got, and up at 12.0 grains, it was within around 20 fps.

Here's the kicker... You may have noticed that I didn't mention primers yet... as that is a little embarrassing. lol I have a lot going on this weekend, and in my quest to get this stuff tested before evening, I grabbed CCI Small PISTOL primers by mistake. At these light loads, they showed no signs of pressure, so I didn't catch it at first. My main question... Are small rifle primers hotter than pistol primers? Would using small rifle primers help make the lower charges more consistent?

The gun shot great. Not a single misfire or failure to cycle in any of the 80 rounds fired, and at 33 yards, most of the bullet holes at the higher charge weights were touching each other. Zero issues with the Berry's Bullets at the 1 in 8 rifling of the PSA barrel. All I did was stick on my existing lower.

Below is the upper:
https://palmettostatearmory.com/psa...eight-m-lok-upper-with-bcg-ch-5165448418.html

Thanks!
 
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H110 and w296 are very inconsistent and you would be better served with almost any other mag pistol powder. Unless you have a near perfect load it sucks. Try 1680 or cfe black.
 
I have plenty of W296/H110, 2400, BCL2, Ramshot TAC, 4227 and CFE BLK. I have no 1680 or Reloader 7. I would like to have some 1680 to try, as that seems like a neat powder for this sort of application. CFE BLK seems like it would be well suited to lighter, supersonic bullets. Most doing subsonic 300 Blackout seem to use the H110. For me (with the pistol primers) it seemed to get really happy once the powder charge went supersonic. I'll probably try the rifle primers and see what happens. If it is still inconsistent at low charges, I'll explore other options... maybe small rifle magnum primers if I can find them, or a different powder.

At least, this is where my mind is at the current time.... All input is still appreciated!
Thanks!
 
Do not use small pistol primers in 300 BO. Long columns of ball powder or more than 10% air space with ball powders could cause it to get pressure spikes. Those spikes are hard on rifle primers I wouldn’t dare chance it on a pistol primer. 1680, CFE BLK would be much better choices and definitely with rifle primers. In this environment you will be in a trade positive situation trading those pistol primers for rifle primers.
 
I have only loaded subs. Before I began, I read up on what I could find on the subject of 300 Blk loading. For the AR-15 platform, it seemed to be unanimous that the faster powders, handgun magnum rates, were not always consistent on cycling at subsonic. But most were good for supersonics. Bolt-action rifles are a whole different story.

At that time CFE Blk wasn't out yet. AA1680 and IIRC, IMR-4198, was mostly what I was seeing reliable data for. Reloder 7 was the only powder I could get my hands on at the time, in the same burn rate.
 
n2omike said:
I have plenty of W296/H110, 2400, BCL2, Ramshot TAC, 4227 and CFE BLK. I have no 1680 or Reloader 7. I would like to have some 1680 to try, as that seems like a neat powder for this sort of application. CFE BLK seems like it would be well suited to lighter, supersonic bullets. Most doing subsonic 300 Blackout seem to use the H110. For me (with the pistol primers) it seemed to get really happy once the powder charge went supersonic. I'll probably try the rifle primers and see what happens. If it is still inconsistent at low charges, I'll explore other options... maybe small rifle magnum primers if I can find them, or a different powder.

At least, this is where my mind is at the current time.... All input is still appreciated!
Thanks!
Click to expand...
That 4227 should be high on your list to test. A mag primer to get the lincon logs started and your off to the races. It would be waaaaay safer and at worst you will get an incomplete burn.
 
I'm thinking about seating the bullets a little deeper... Right now they are at 2.150". Thoughts about going to 2.090" to 2.100"?
The powder worked great at higher loads, and have twenty loaded with10.5 grains of W296/H110 sitting there. Was thinking about seating them a little deeper.

My initial thoughts... If it does work, it will probably make them go supersonic. lol Thoughts?
 
I am loading 10.1 gr of 4227 under that 220gr Berry Bullet at OAL of 2.19. I am getting 1040 fps from a 16 inch barrel and 980 fps from a 9-inch barrel. 4227 is noticeably quieter than H110 in my SDN-6 suppressor. I am using Accurate 1680 to push Maker Rex 220 gr all copper bullets. The 4227 would not cycle when pushing the Maker Rex bullets.
 
I decided to leave the 10.5 grain H110 as-is, as they are truly fun to shoot subsonic... even if they aren't that consistent. lol Gun cycled 100% all the way from 9.5 to 12.0 grains, and after a total of 80 rounds, looked extremely clean.

I did have 18 cases left over with the Small Pistol Primers, so I loaded them up with 9.5, 10.0, 10.5 and 11.0 grains of 4227 to see how that works. Everything still at 2.150". Will probably not get to test this weekend, but it will be waiting for when the time/weather agrees. Would still like to acquire some 1680 to see how that works.

Thanks for the input!
 
n2omike said:
I decided to leave the 10.5 grain H110 as-is, as they are truly fun to shoot subsonic... even if they aren't that consistent. lol Gun cycled 100% all the way from 9.5 to 12.0 grains, and after a total of 80 rounds, looked extremely clean.

I did have 18 cases left over with the Small Pistol Primers, so I loaded them up with 9.5, 10.0, 10.5 and 11.0 grains of 4227 to see how that works. Everything still at 2.150". Will probably not get to test this weekend, but it will be waiting for when the time/weather agrees. Would still like to acquire some 1680 to see how that works.

Thanks for the input!
Click to expand...
Most magnum powders will give you more consistency with mag primers. I got the best results in 357 at the max load and mag primers before it really started to clean up.
 
Thanks for the replies. I must say, this gun is extremely fun to shoot! With the muffler, it's extremely quiet and no hearing protection is needed at all. I have an old steel air cylinder that is around 2 ft tall... and when that 220 grain copper plated bullet strikes that thing, the impact is LOUD! It's fun to hang up... then make it dance! lol Solid hits put nice dents in the thing, but don't penetrate... so it should last a long time. If you have a 300 AAC with a muffler and have not done this... I HIGHLY recommend it! Word of warning... You will not go home with any ammo, so don't take any more than you plan to shoot. :)

The Berry's Bullets 220 grain copper plated bullets are fairly inexpensive... for a copper plated 220 grain projectile... and shoot great. They are also available at most places right now.
 
Steel Valley Casting's 220 grn Hi-Tek coated cast bullets are cheaper than Berry's, at 17 cpr, if you haven't discovered them for volume shooting yet. My personal load for those is 12.6 grns of CFE Blk with Win small std RIFLE primers, lol, set to 2.155" COAL. That gets me to 1,089 fps with a 10.3" DD heavy barrel (AR-15), and 2.25 MOA (5 shots) with a red dot. I've been meaning to swap the red dot out with a decent scope to further precision test and suspect that load may hover around 1 to 1.5 MOA when I do. If I wanted to squeeze velocity towards the subsonic boundary, 12.8 grns gets me to 1,110 fps, but there's a big jump in noise with those additional 0.2 grns, even with a can, which isn't worth it to me.

https://www.steelvalleycasting.com/product/300-blk-hi-tek-220grn-bullet/
 
Gone Hiking said:
Steel Valley Casting's 220 grn Hi-Tek coated cast bullets are cheaper than Berry's, at 17 cpr, if you haven't discovered them for volume shooting yet. My personal load for those is 12.6 grns of CFE Blk with Win small std RIFLE primers, lol, set to 2.155" COAL. That gets me to 1,089 fps with a 10.3" DD heavy barrel (AR-15), and 2.25 MOA (5 shots) with a red dot. I've been meaning to swap the red dot out with a decent scope to further precision test and suspect that load may hover around 1 to 1.5 MOA when I do. If I wanted to squeeze velocity towards the subsonic boundary, 12.8 grns gets me to 1,110 fps, but there's a big jump in noise with those additional 0.2 grns, even with a can, which isn't worth it to me.

https://www.steelvalleycasting.com/product/300-blk-hi-tek-220grn-bullet/
Click to expand...

Yours might be some of the best info yet. I have a 10.5" barrel, so your load data compares pretty well... plus that link shows people having good luck with the CFE BLK. Might develop a load close to yours... and maybe even try out some of those coated bullets. Plain lead bullets leave a MESS... and the copper plated Berrys are absolutely clean. Are these nice and clean as well? Thanks!
 
kcofohio said:
At $40.50 per 250, Missouri's 245 gr. Hi-Tek coated bullet is the lowest price I have found, and clean also.
https://missouribullet.com/details.php?prodId=347&category=6&secondary=36&keywords=
Click to expand...

Good bullets for bolt guns, but unfortunately, many with a 300 Blk in an AR configuration have trouble with those feeding, myself included. The blunt nose doesn't play well with the feed ramps. I tried various seating depths and two buffer springs. Switching to 300 Blk - specific Lancer mags helped somewhat, but I finally gave up on them. I still have two or three hundred to practice malfunction drills. :eek:

Since some do have success with them, I believe the difference is likely in the geometry of the feed ramps between different guns. Of course, there's only one way of finding out if they'll function in your gun. I'd just advise against making an initial purchase of say, 500 or more. ;)
 
Gone Hiking said:
Good bullets for bolt guns, but unfortunately, many with a 300 Blk in an AR configuration have trouble with those feeding, myself included. The blunt nose doesn't play well with the feed ramps. I tried various seating depths and two buffer springs. Switching to 300 Blk - specific Lancer mags helped somewhat, but I finally gave up on them. I still have two or three hundred to practice malfunction drills. :eek:

Since some do have success with them, I believe the difference is likely in the geometry of the feed ramps between different guns. Of course, there's only one way of finding out if they'll function in your gun. I'd just advise against making an initial purchase of say, 500 or more. ;)
Click to expand...

Good thing nobody told me that beforehand. ;)

I've ran them through 2 different pistol uppers with no problems. Maybe I got lucky. :)

BTW, I seat the Missouri bullet to 2.100" OAL.
 
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