300 BLK suppressed AR Pistol subsonic reloading

[GreyBeardBiker]

Good morning! New to this forum but an old hand at other firearms/reloading forums. I am an experienced reloader having rolled my own ammo for over 20 years. I have loaded 300 BLK subsonic/supersonic for carbine length ARs for five years - with very good results.

Last May I purchased a SIG Sauer Rattler with an 8" barrel. I have only shot the pistol a few times as I was waiting for my tax stamp for a suppressor. After nine months I finally picked up my suppressor last Wednesday. Taking it to the range with 208gr HPBT reloads, which worked for my 16" barreled AR, provided quiet shots, but they are obviously too under-powered to cycle the pistol. I have tons of new reloading guides from Hodgdon, Speer, Hornady and Lyman. Unfortunately, none of the manuals provide a starting point for an 8" AR 300 BLK. Where does one even begin?


The carbine length subsonic recipe for the AR is:
208gr Hornady BTHP
8.1gr Vihta Vuori N110
Remington 5 1/2 small rifle primer
New Starline brass
COAL 2.250"


I also have Hodgdon H110 which works well for the carbine. Accurate 1680 seems to be the most popular powder, but burn rates for the H110/N110 seem similar. Has anyone worked up subsonic loads for 8" 300 BLK with either of the powders I have?

Mike
Clarksville, TN

 

[nobbie333actual]

Did you try adjusting your gas on your MCX

 

[GreyBeardBiker]

Did you try adjusting your gas on your MCX

Yes, but based on several things members have sent me, the dope I was using was way too light for that short of barrel. Thanks!

 

[Dogtown]

8.1gr of N110 is getting close to the danger zone with a 70% case fill. That's even slightly lower than VV's starting load.

For reference, I'm shooting 200gr bullets with 14gr of TAC - similar load as yours but closer to 97% case fill.

EDIT: here's AA2460

 

[GreyBeardBiker]

8.1gr of N110 is getting close to the danger zone with a 70% case fill. That's even slightly lower than VV's starting load.

For reference, I'm shooting 200gr bullets with 14gr of TAC - similar load as yours but closer to 97% case fill.

The 8.1 N110 did work well on my 16" AR - even being near the starting load. I was pointed to a thread on the 300BLK forum using 9.8gr of N110.

 

[M4orturnate]

Try a heavier bullet if your gun is picky. Coated 220g work great in my 6". H110 is a great powder but lil gun is my favorite. Definitely the queitest ive tested

 

[GreyBeardBiker]

Try a heavier bullet if your gun is picky. Coated 220g work great in my 6". H110 is a great powder but lil gun is my favorite. Definitely the queitest ive tested

I appreciate it. I am going to load a spread of 9 to 9.5gr of H110 with my 200s. I'm guessing that will do the trick. Should be no risk other than going supersonic.

 

[redbullitt]

Hopefully that works out for you. If not, 1680 and cfeblk have run EVERYTHING picky ive dealt with very well. They are noisy, but also super gassy. Lil gun may work and 4227 could be worth a try depending on what you can get.

I agree with the suggestion of a heavier bullet. Should give more wiggle room for charge weight. 208 amax has been noticeably more picky on powder to run reliably than the 220s.

Hell, ive seen a daniel defense 7inch or maybe it was 8? barrel 300blk, 250g cast coated running clear down under 700fps with cfeblk. It has its downsides, but reliability on short guns hasnt been one ive seen fwiw.

 

[alamo5000]

I have a bunch of 300BLK powders and lately I've been using some shooter's world powders. The Blackout powder and the SOCOM powder are both excellent choices. The SOCOM requires just a small amount less powder to get similar results. That means back off .1 grain and you are right there.

I have a bunch of 190 grain bullets that I bought a long time ago. That light of a grain weight is super tricky to get a reliable subsonic round that still cycles the rifle like it's supposed to. A 208 grain bullet would be a lot easier to work with. That said with 300BLK there are essentially two areas that can be tricky to navigate. One is really short barrel lengths. The dwell time from the port to when the bullet exits the barrel can be really short so this can create complications. There are however good powders out there, albeit not ALL common Blackout powders would work given the circumstances. The second tricky issue is bullet weight. Any traditionally constructed bullet (not copper solids) that are sub 200 grains can also create a problem. I've found that the 200 grain or below bullet weight requires a lot more trial and error for powder choices. Anything above 200 grains generally speaking opens up a whole lot more good powder options.

It's definitely easy to go down a lot of rabbit holes with 300BLK, but suffice it to say that H110 should give you good results as will AA1680. With that bullet you should have about 25-30 viable powder choices to make things work.

My host is a suppressed 9" AR.

 

[GreyBeardBiker]

I appreciate all of the advice. I am going to work up some dopes with the H110 today and head to the range in the morning!

 

[creekside]

Hell, ive seen a daniel defense 7inch or maybe it was 8? barrel 300blk, 250g cast coated running clear down under 700fps with cfeblk. It has its downsides, but reliability on short guns hasnt been one ive seen fwiw.

Agreed. CFE black works well for me with 200/220 gr Berrys. Will try it - and other powders - with 190 gr sub-X now, just got a couple of boxes last week.

 

[creekside]

I appreciate all of the advice. I am going to work up some dopes with the H110 today and head to the range in the morning!

I'm also about to work up some loads with N110 and perhaps H110 for my 8.5" SBR. I have both powders for 30 carbine and I'm eager to try them in 300 for 190, 200, and 220 gr. subsonic loads.

 

[GreyBeardBiker]

I look forward to learning about the loads both of you work up!

 

[GreyBeardBiker]

Good morning! New to this forum but an old hand at other firearms/reloading forums. I am an experienced reloader having rolled my own ammo for over 20 years. I have loaded 300 BLK subsonic/supersonic for carbine length ARs for five years - with very good results.

Last May I purchased a SIG Sauer Rattler with an 8" barrel. I have only shot the pistol a few times as I was waiting for my tax stamp for a suppressor. After nine months I finally picked up my suppressor last Wednesday. Taking it to the range with 208gr HPBT reloads, which worked for my 16" barreled AR, provided quiet shots, but they are obviously too under-powered to cycle the pistol. I have tons of new reloading guides from Hodgdon, Speer, Hornady and Lyman. Unfortunately, none of the manuals provide a starting point for an 8" AR 300 BLK. Where does one even begin?


The carbine length subsonic recipe for the AR is:
208gr Hornady BTHP
8.1gr Vihta Vuori N110
Remington 5 1/2 small rifle primer
New Starline brass
COAL 2.250"


I also have Hodgdon H110 which works well for the carbine. Accurate 1680 seems to be the most popular powder, but burn rates for the H110/N110 seem similar. Has anyone worked up subsonic loads for 8" 300 BLK with either of the powders I have?

Mike
Clarksville, TN

*UPDATE*

I worked up the following load with the N110:
Brass: Starline (new)
Primer: Remington small rifle
Bullet: 208gr Hornady BTHP Match
Powder: 9.7gr N110
COAL: 2.240"

This load did not work with the gas valve in the normal setting, but did when I turned it to the alternate gas valve setting. This was very quiet suppressed and definitely was not supersonic. The indoor range I went to did not allow me to bring my chronograph, so I do not have velocity information for it. Any suggestions on what might prevent the rifle from cycling in the standard gas position? I am assuming this would be an indication that the load is still a bit under-powered? I am considering a slightly deeper bullet depth, but I am very pleased with the accuracy and consistency the way it is. The other option, would be to bring the powder charge up a couple of tenths. Thanks!

GBB

 

[creekside]

Since you're in load development, not getting velocities at the indoor range is a bummer, but you can infer that it may be underpowered. I prefer to immediately test a few on chrono out back when I'm able, but if I'm shooting something unsuppressed, I'll go to the range. In that case, I'll step my charges within data range and see what works best. So you still won't have velocity but if you had a loads .2,.4,.6 gr. etc. heavier, you may learn what cycles your rifle.

I much prefer to stamp a few out and shoot 'em because the above is a bit tedious. Chrono at the club is a pain and can slow the line down a bit when I'm trying to get it adjusted right so I don't shoot it. Once I get a load dialed in I really just want to crank them out

I haven't loaded 300 AAC with N110 but I did load 100 M1-30 Carbine this AM and it meters well. I just took a chance on those after making similar load with H110. I don't usually make 100 and then go see how they shoot.

 

[GreyBeardBiker]

Since you're in load development, not getting velocities at the indoor range is a bummer, but you can infer that it may be underpowered. I prefer to immediately test a few on chrono out back when I'm able, but if I'm shooting something unsuppressed, I'll go to the range. In that case, I'll step my charges within data range and see what works best. So you still won't have velocity but if you had a loads .2,.4,.6 gr. etc. heavier, you may learn what cycles your rifle.

I much prefer to stamp a few out and shoot 'em because the above is a bit tedious. Chrono at the club is a pain and can slow the line down a bit when I'm trying to get it adjusted right so I don't shoot it. Once I get a load dialed in I really just want to crank them out

I haven't loaded 300 AAC with N110 but I did load 100 M1-30 Carbine this AM and it meters well. I just took a chance on those after making similar load with H110. I don't usually make 100 and then go see how they shoot.

It is definitely nice to come up with a consistent load and just load up a couple of hundred. I am definitely not there yet. Thanks for your feedback!

 

[oso1]

I load with H 110 and CFE Black, 190 sub x and 220 plated, I keep velocity at 990 fps. I tried some coated bullets but I found too much lead in suppressor at shooting the coated bullets so I just stick with plated or jacketed.

 

[creekside]

I look forward to learning about the loads both of you work up!

Just following up on load development.

I loaded 8.3 gr N110 with Berrys 200 gr, reliable sub and cycling.

Switched to IMR 4227, using 10 gr behind Berry's 200 gr, reliable sub and cycling.

Also loaded IMR 4227 with 190 gr Sub-X, had to back it down to 9.4 gr to keep it sub out of 8" barrel.

IMR 4227 is now my favorite powder for 300 AAC subs. It meters well, cycles well, seems clean. I need to go back to the N110 to compare; it works just fine, perhaps equally well. Just need to spend some more time with it.

Berry's 220 gr also work with 10 gr. 4227. Keeps it simple and I can affect velocity by choosing either my bolt gun or the AR pistol.

 

[bigpeddler]

I load with H 110 and CFE Black, 190 sub x and 220 plated, I keep velocity at 990 fps. I tried some coated bullets but I found too much lead in suppressor at shooting the coated bullets so I just stick with plated or jacketed.

Will you share your 190 sub / CFE BLK recipe? What length barrel?

 

[laflaone]

Good morning! New to this forum but an old hand at other firearms/reloading forums. I am an experienced reloader having rolled my own ammo for over 20 years. I have loaded 300 BLK subsonic/supersonic for carbine length ARs for five years - with very good results.

Last May I purchased a SIG Sauer Rattler with an 8" barrel. I have only shot the pistol a few times as I was waiting for my tax stamp for a suppressor. After nine months I finally picked up my suppressor last Wednesday. Taking it to the range with 208gr HPBT reloads, which worked for my 16" barreled AR, provided quiet shots, but they are obviously too under-powered to cycle the pistol. I have tons of new reloading guides from Hodgdon, Speer, Hornady and Lyman. Unfortunately, none of the manuals provide a starting point for an 8" AR 300 BLK. Where does one even begin?


The carbine length subsonic recipe for the AR is:
208gr Hornady BTHP
8.1gr Vihta Vuori N110
Remington 5 1/2 small rifle primer
New Starline brass
COAL 2.250"


I also have Hodgdon H110 which works well for the carbine. Accurate 1680 seems to be the most popular powder, but burn rates for the H110/N110 seem similar. Has anyone worked up subsonic loads for 8" 300 BLK with either of the powders I have?

Mike
Clarksville, TN

I use 11.5 gn Accurate 1680 for a 200 gn FMJ bullet in my Adams Arms 300 blk 8" piston AR pistol, and my IMI X95 Tavor in 300 blk. No issues. I like the 1680.

 

[Bobby Ball]

I've been doing 11.3 of cfe blk with 175 sub-x, cci sr , 2.005 coal.

 

[NCHillbilly]

I'm also using 11.5 grs of 1680 under a 208 gr hornady hpbt, with LC cases and cci 34 primers. 7.5" bbl, fixed gas block. Runs about 1050 fps, functions flawlessly suppressed or not. Plenty accurate for what the weapon was built for.
I recently got some 190 sub-x's to try, but haven't shot them yet.