300 Blackout subsonic load data for bolt action w/7.5" barrel

[Konocti's Wigwam]

The reason I don’t feel CFE is worth the hassle for supers is that I can use 296/H110, have the same accuracy or better with almost 10% more velocity than CFE with bullets under 150 grains.

I have a couple lbs. of 296 and H110 also, which I was loading for 300 blackout about 6 or 7 years ago. 150 gr is what I would load for 308.

Over 150 grains it’s a similar story with 1680 or Shooters World Blackout.

Looking at the powder, CFEBLK looks identical to Accurate 1680, it is not extruded, but very small spherical. Looks like it would meter well in a progressive, which I don't use anymore. Both have the same mixed color with metalic pieces in it. My gut tells me they could be the same powder, but I have nothing to confirm that. Oh yeah, I also have about 6 lbs. of 1680.

The problem was it burned so dirty that the trigger group failed after about 6 shots.

I've never seen any powder that fires that dirty, but will report back on my next range trip. I have fired 400-500 rounds of 5.56 and the action was still operating just fine. OTOH, if I ever need to shoot 6 shots at a pig, I better get back to the range and practice a bit more. Even 3-4 MOA is gonna put meat in my freezer.

A lot goes into putting together a clean and quiet AR. But it can be done.

I wanna build bolts. ARs are not that challenging. I'd rather build 1911s, they can also be quite challenging.

My experience wth the cartridge includes barrels from 6-24” both bolt action and gas operated. Powder selection and matching it to the bullet is the key.

I've only built 7.5" - 16". I have longer 26" barrels, but on 308, which could be a perfectly fine hunting rifle, just a tad heavy.

 

[Oso]

Dellet - Is always a pleasure reading your write-ups. I agree about CFEBLK being a second choice powder for 300BO. H110 works great in my 8" AR for both supers and subs. VV N110 loads were accurate and extremely clean burning. For supersonic loads H110 generated greater velocity. I decided to dedicate N110 to subsonics.

Unfortunately, I am also running a 300HAM'R with the preferred powder being CFEBLK. I forgot how dirty it was. You are right in that it performs best at full or lightly compressed loads.

 

[Hoser]

I tried some pistol powders like Universal Clays, Bullseye and Red Dot and while accuracy was about 1 MOA, the ES was much higher than I liked. Hollywood quiet though. 1680 and CFEBLK were ok, but much louder and dirtier than anything else I had tried.

Trailboss was a bust. Pretty solid ES but velocity was too low. I couldnt get above 900 fps without pressure.

One thing that is still making me chase my tail is cold and warm bore fliers. First shot from a cold bore is about 3 MOA low. The rest go right into a little group that makes me smile. Even out to 300 yards accuracy is excellent, other than that first shot. Let it sit for 3-5 minutes, same thing. I changed scope, bullets, powder, brass, seating depth, coated and uncoated bullets. All charges weighed on an A&D Fx-120 to within 0.02 gns.

This was a new Brux 8 twist barrel and Thunderbeast Magnus can. Even after putting 450 rounds of supersonic ammo through it, still does it thing. Finally gave up and just accepted that the first shot will always be low.

 

[dellet]

Dellet - Is always a pleasure reading your write-ups. I agree about CFEBLK being a second choice powder for 300BO. H110 works great in my 8" AR for both supers and subs. VV N110 loads were accurate and extremely clean burning. For supersonic loads H110 generated greater velocity. I decided to dedicate N110 to subsonics.

Unfortunately, I am also running a 300HAM'R with the preferred powder being CFEBLK. I forgot how dirty it was. You are right in that it performs best at full or lightly compressed loads.

So far I’ve managed to avoid the 300 Ham’r, tho not without cost. Two other cartridges have caught my attention, one is basically a 300 Ham’r rimmed.


Top to bottom, 300 BLK, 32-30 Remington fire formed in my rifle, 32-30 original cartridge, 30-30 Wesson.

The 32-30 actually used a 125 grain .308 bullet, cases are made from full length 357 Max brass. The difference between the 32-30 Rem and the 30-30 Wesson is the shoulder. The Wesson is a straight taper to a neck and came in either 165 or 185 grain bullets, both grooved and paper patched. I don’t think either cartridge survived past about 1910.

Here’s the 32-30 and rounds formed in a 300 BLK die.





It’s kinda fun when people ask what I’m shooting and I tell them Rimmed 300 Ham’r

 

[oaklandraider76]

Well I got the brass problem resolved and am loading some rounds. Gonna start with Hornady 220 gr ELD-X bullets in front of 8.3 grains of Accurate #9 and ladder down. I am loading on a single stage press and am meticulous when it comes to weighing powder charges. We will see what it clocks in at. Again, thanks for all the help and good advice from members of this forum.

 

[oaklandraider76]

So far I’ve managed to avoid the 300 Ham’r, tho not without cost. Two other cartridges have caught my attention, one is basically a 300 Ham’r rimmed.
View attachment 1504833

Top to bottom, 300 BLK, 32-30 Remington fire formed in my rifle, 32-30 original cartridge, 30-30 Wesson.

The 32-30 actually used a 125 grain .308 bullet, cases are made from full length 357 Max brass. The difference between the 32-30 Rem and the 30-30 Wesson is the shoulder. The Wesson is a straight taper to a neck and came in either 165 or 185 grain bullets, both grooved and paper patched. I don’t think either cartridge survived past about 1910.

Here’s the 32-30 and rounds formed in a 300 BLK die.

View attachment 1504838

View attachment 1504839

It’s kinda fun when people ask what I’m shooting and I tell them Rimmed 300 Ham’r

That is a beautiful rifle!

 

[oaklandraider76]

Results from first range trip.

300 Blackout
220 gr Hornady ELD-X
Accurate #9
COAL 2.255”
CCI 400 primers
n=5 rounds

8.5 gr, mean velocity 1107 fps, ES=20, SD=7

8.3 gr, mean velocity 1089 fps,
ES=17, SD=6

8.1 gr, mean velocity 1064 fps, ES=41, SD=15

 

[dellet]

Results from first range trip.

300 Blackout
220 gr Hornady ELD-X
Accurate #9
COAL 2.255”
CCI 400 primers
n=5 rounds

8.5 gr, mean velocity 1107 fps, ES=20, SD=7

8.3 gr, mean velocity 1089 fps,
ES=17, SD=6

8.1 gr, mean velocity 1064 fps, ES=41, SD=15

Now. Figure out how much bullet you have in the case, and seat the 190 close to the same depth if possible. I don’t remember what length it will be at the cannelure, but that will have less bullet in the case, lower load density. I think the bullet length difference is about .300”, but the -90 will jam pretty short compared to the ELD.

What will happen is the lower load density will drop velocity due to a lower pressure curve or burn rate of the powder. This will help balance out the higher velocity due to the lighter bullet. It’s very interesting to watch those number. This is why I say I fine tune velocity with seated depth.

A normal load you look for accuracy nodes and except the velocity. With subs you have a velocity window and to a certain extent accept accuracy. That’s why people struggle with accuracy in a gas gun, you have the third factor of needing to cycle the action.

If you start to see the patterns of manipulating the burn rate of the powder with seated depth, you can maintain the velocity while compensating for jump and also maintain muzzle pressure for cycling.

Forgot to ask.
What did you think of the sound difference using #9 in short barrel vs the other powders in a 16”?

 

[oaklandraider76]

Now. Figure out how much bullet you have in the case, and seat the 190 close to the same depth if possible. I don’t remember what length it will be at the cannelure, but that will have less bullet in the case, lower load density. I think the bullet length difference is about .300”, but the -90 will jam pretty short compared to the ELD.

What will happen is the lower load density will drop velocity due to a lower pressure curve or burn rate of the powder. This will help balance out the higher velocity due to the lighter bullet. It’s very interesting to watch those number. This is why I say I fine tune velocity with seated depth.

A normal load you look for accuracy nodes and except the velocity. With subs you have a velocity window and to a certain extent accept accuracy. That’s why people struggle with accuracy in a gas gun, you have the third factor of needing to cycle the action.

If you start to see the patterns of manipulating the burn rate of the powder with seated depth, you can maintain the velocity while compensating for jump and also maintain muzzle pressure for cycling.

Forgot to ask.
What did you think of the sound difference using #9 in short barrel vs the other powders in a 16”?

Again, thanks for the good dope. As for the #9 it is quiet and "snappy". I like it. Also MUCH cleaner than the CFE BLK.

 

[oaklandraider76]

Well, I'm settled in on a favorite load for now. 8.0 grains Accurate #9 pushing 220 grain Hornady ELD-X bullets. Consistent sub-sonic velocities and very accurate.

 

[Stugots]

I tried some pistol powders like Universal Clays, Bullseye and Red Dot and while accuracy was about 1 MOA, the ES was much higher than I liked. Hollywood quiet though. 1680 and CFEBLK were ok, but much louder and dirtier than anything else I had tried.

Trailboss was a bust. Pretty solid ES but velocity was too low. I couldnt get above 900 fps without pressure.

One thing that is still making me chase my tail is cold and warm bore fliers. First shot from a cold bore is about 3 MOA low. The rest go right into a little group that makes me smile. Even out to 300 yards accuracy is excellent, other than that first shot. Let it sit for 3-5 minutes, same thing. I changed scope, bullets, powder, brass, seating depth, coated and uncoated bullets. All charges weighed on an A&D Fx-120 to within 0.02 gns.

This was a new Brux 8 twist barrel and Thunderbeast Magnus can. Even after putting 450 rounds of supersonic ammo through it, still does it thing. Finally gave up and just accepted that the first shot will always be low.

Beautiful Rifle! Can you tell me more about it?