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

[oaklandraider76]

Well. I just measured the headspace of the rounds that didn't fire and they are 11 thousandths below zero (=1 on the Wilson Case Gauge Micrometer). Wow. Then checked the unfired Hornady brass and the same. No wonder the light primer strikes. Amazing that these rounds run in the gas gun without any hiccups. Well, I feel more than a bit stupid but another lesson learned.

 

[oaklandraider76]

Forgot to say that the formed (= fired) cases mike at about -0.004, so the shoulder has moved forward by about 0.007".

 

[dellet]

Forgot to say that the formed (= fired) cases mike at about -0.004, so the shoulder has moved forward by about 0.007".

That’s not necessarily true. Since they fired, they might not have been as short. You’ll need to check some before and after to know for sure.

Sounds like loading so the bullet is touching the lands. Headspacing off the bullet is probably in your future.

If you haven’t already, you might get the loaded ones to fire with repeated strikes, or just fire them in your AR and don’t allow the shoulder to touch when sizing.

 

[oaklandraider76]

Good point(s). I will do that. As for powders on hand I have Accurate #9 and Lil'Gun. Not much else that will work with the 300 BLK. Again, thanks for all the advice.

 

[oaklandraider76]

I also have a lot of blue dot which I use to load 10 mm. But I have not seen anyone that uses that powder for 300 blackout loads.

 

[6Creed73]

I also have a lot of blue dot which I use to load 10 mm. But I have not seen anyone that uses that powder for 300 blackout loads.

Blue dot is quite a bit faster than CFE-BLK, so it could possibly be a decently quiet load. Like I mentioned earlier, a bolt gun opens new possibilities with 300BLK.

People use a lot of different powders that typically aren't used with 300BLK. Just make sure you work down with your ladders so you don't stick a bullet. Also, when experimenting with powders that don't have published data, remove the can during initial testing to make sure the bullet is stable. A baffle strike would suck.

 

[dellet]

Ok Good point(s). I will do that. As for powders on hand I have Accurate #9 and Lil'Gun. Not much else that will work with the 300 BLK. Again, thanks for all the advice.

You might surprised what works well for subs when you don’t have to worry about cycling.

Blue dot is quite a bit faster than CFE-BLK, so it could possibly be a decently quiet load. Like I mentioned earlier, a bolt gun opens new possibilities with 300BLK.

People use a lot of different powders that typically aren't used with 300BLK. Just make sure you work down with your ladders so you don't stick a bullet. Also, when experimenting with powders that don't have published data, remove the can during initial testing to make sure the bullet is stable. A baffle strike would suck.

When you get into really fast powders and the unknown, it’s better to work up your load. Blue dot falls into that category. There is a bit of information out there of people using it. Mostly with 175 grain and lighter bullets.

You need to weigh the possibility of a stuck bullet verse 90.000 psi. In a short barrel of 7.5”, the probability of a stuck bullet is pretty low. The possibility of a popped primer is probably greater.

This is where something like quickload is really needed to get some kind of idea what pressures are.

 

[6Creed73]

You might surprised what works well for subs when you don’t have to worry about cycling.

When you get into really fast powders and the unknown, it’s better to work up your load. Blue dot falls into that category. There is a bit of information out there of people using it. Mostly with 175 grain and lighter bullets.

You need to weigh the possibility of a stuck bullet verse 90.000 psi. In a short barrel of 7.5”, the probability of a stuck bullet is pretty low. The possibility of a popped primer is probably greater.

This is where something like quickload is really needed to get some kind of idea what pressures are.

That's a good point, I've always worked down when developing subs, but am just now getting into the faster pistol powders. I use GRT to make sure the pressures are safe. My bolt gun is a 16" barrel...I'll probably work down like I typically do for subs, using GRT to make sure pressures are good to go. Working down just feels safer to me.

 

[oaklandraider76]

That's a good point, I've always worked down when developing subs, but am just now getting into the faster pistol powders. I use GRT to make sure the pressures are safe. My bolt gun is a 16" barrel...I'll probably work down like I typically do for subs, using GRT to make sure pressures are good to go. Working down just feels safe

You might surprised what works well for subs when you don’t have to worry about cycling.

When you get into really fast powders and the unknown, it’s better to work up your load. Blue dot falls into that category. There is a bit of information out there of people using it. Mostly with 175 grain and lighter bullets.

You need to weigh the possibility of a stuck bullet verse 90.000 psi. In a short barrel of 7.5”, the probability of a stuck bullet is pretty low. The possibility of a popped primer is probably greater.

This is where something like quickload is really needed to get some kind of idea what pressures are.

I just measured 40 new from the box Hornady cases with the Wilson gauge and all of them fell between -0.009 and -0.011”. Hmmm. It is no wonder I’m getting so many light primer strikes with the bolt gun.

 

[dellet]

Took me awhile to find this.
Years ago on 300blktalk we compared factory brass base to datum measurements. It was flawed in the sense that multiple people with multiple tools did the measuring, but when you look at the variation the same people got using their tool it’s no wonder factory ammo sucks.

Some rounds close to .010” under minimum.

Handloading Basic and Advanced Chapter 2 » 300BlkTalk

 

[mic2377]

The absolute quietest loads are a light bullet and a very fast burning powder. Two of my favorite loads are 3.9-4.0 gr of Red Dot under a 110 gr Vmax, or 5.2 gr under a 150 gr Speer. As quiet as a 22 subsonic!

The problem with loads with these powders is that there is no real published load data. They are very fast burning and do pose a very significant safety hazard if double charged (like guaranteed to explode your weapon).

I have also experimented with N340 and Bullseye too.

I also agree your case shoulder is off as the potential reason for your light strikes

 

[XTR]

If you’re having brass sizing issues do what wildcatters do blowing the shoulder out. Run some full power (not max power) at a hard jam to fire form.

with low power loads you can try shooting with a light coat of Imperial on the cases. It will keep them from gripping the chamber and might get you fully formed to the chamber. I wouldn’t do that with full power cases, it’ll increase bolt thrust.

 

[6Creed73]

Here is a load I'm currently working on with a 150gr bullet and N320. Even with N320 being a fast powder GRT shows well below pressure max, so I'll definitely be working this ladder down. I'm thinking I'll probably end up somewhere around 5gr.

I don't have access to Quickloads, but would be curious to see if GRT and Quickloads are pretty close with their pressure estimates.

My only real concern is around case fill. @dellet, do you use any case filler like poly fill with loads like this?

 

[oaklandraider76]

I appreciate all the good info you guys are providing and your willingness to share. As soon as I get the head space issue worked out I will be diving into the load data. I'm sure glad I put my finger on the problem before I called Christensen tech support to complain about the rifle. Well, I guess this is what makes it fun.

 

[dellet]

Here is a load I'm currently working on with a 150gr bullet and N320. Even with N320 being a fast powder GRT shows well below pressure max, so I'll definitely be working this ladder down. I'm thinking I'll probably end up somewhere around 5gr.

I don't have access to Quickloads, but would be curious to see if GRT and Quickloads are pretty close with their pressure estimates.

My only real concern is around case fill. @dellet, do you use any case filler like poly fill with loads like this?

I never have fooled around with fillers, shooting suppressed that seem like a good way to fill it up with crap that won’t burn out.

What will do is compare load data and powders. A good example would be 296/H110. There used to be prominent warnings all over load data that you should never down load those powders. Reduced loads were “known to go kaboom”. Now it seems the problem was more of a revolver dynamic where the bullet started, stopped at the forcing cone and spiked pressure. No more warnings.

There are bikers I shoot in the blackout that jump more than 1/4”, how’s that different than a revolver?



So you’re looking at N320. What are the favorite loads in cartridges that is actually designed for?

What’s the case fill ratio?

You might find that the powder excels with a 50% density. I would start my load somewhere around there.

Accurate #2 is a low load density designed powder. Works great for hand fed blackout subs. Clean, quiet, and over 1000 rounds to a pound.

As long as peak pressure is under 60.000, I’m more concerned with muzzle pressure. The lower the muzzle pressure, the quieter the shot will be. Short barrels this is the key. This is why subs out of an AR are very disappointing the first time
You hear one. Slow powders that will reliably cycle, are loud, dirty, and blow smoke in your face. H110/296 are pretty good, but by the time you get to something like #9 it completely changes the game. That’s when an AR is quieter than a nail gun, and can push rimfire noise levels.

That’s why GRT and quickload are almost a must if you are a serious subsonic shooter. You have to be able understand and map pressure curves. When you can change seated depth and change muzzle pressure 500 psi. It makes a huge difference at the ear, and may mean the difference if the load cycles a gas gun.

 

[6Creed73]

I never have fooled around with fillers, shooting suppressed that seem like a good way to fill it up with crap that won’t burn out.

What will do is compare load data and powders. A good example would be 296/H110. There used to be prominent warnings all over load data that you should never down load those powders. Reduced loads were “known to go kaboom”. Now it seems the problem was more of a revolver dynamic where the bullet started, stopped at the forcing cone and spiked pressure. No more warnings.

There are bikers I shoot in the blackout that jump more than 1/4”, how’s that different than a revolver?



So you’re looking at N320. What are the favorite loads in cartridges that is actually designed for?

What’s the case fill ratio?

You might find that the powder excels with a 50% density. I would start my load somewhere around there.

Accurate #2 is a low load density designed powder. Works great for hand fed blackout subs. Clean, quiet, and over 1000 rounds to a pound.

As long as peak pressure is under 60.000, I’m more concerned with muzzle pressure. The lower the muzzle pressure, the quieter the shot will be. Short barrels this is the key. This is why subs out of an AR are very disappointing the first time
You hear one. Slow powders that will reliably cycle, are loud, dirty, and blow smoke in your face. H110/296 are pretty good, but by the time you get to something like #9 it completely changes the game. That’s when an AR is quieter than a nail gun, and can push rimfire noise levels.

That’s why GRT and quickload are almost a must if you are a serious subsonic shooter. You have to be able understand and map pressure curves. When you can change seated depth and change muzzle pressure 500 psi. It makes a huge difference at the ear, and may mean the difference if the load cycles a gas gun.

Thanks, as usual you're a wealth of knowledge on this unique cartridge.

I agree with you 100% about the use of GRT/Quickload...300BLK is what got me started with using GRT.

 

[Konocti's Wigwam]

Well, I took the Christensen MPP 300BLK to the range today and about 20% of the rounds chambered failed to detonate due to light primer strikes. Hmmm.

This data is from the Hodgdon site for CFEBLK. I don't have any complaints with CFEBLK so far. It is almost identical to Accurate 1680, which has long been the standard for BLK, it is available which is a HUGE plus, and it only costs $38/lb at my local Sportsman's Wharehouse. I have 5 lbs. of it and it works ok so far. I'm not shooting subsonic though, I'm shooting 110gr and 120gr Barnes TTSX, using their load data as a reference. Aside from any load data, I think EVERYONE needs to test fps in their own rifle. There are too many variances.

Twist: 1:8.000"
Barrel Length: 16.000"
Trim Length: 1.363"
Bullet: 208 GR. HDY A-MAX
Diameter: 0.308"
Case: Hornady
Primer: Remington 7 1/2, Small Rifle Magnum
COL: 2.260"
Max load: 11.6 gr

FWIW, I would check your seating depth on the light primer strikes. Quite honestly I think the Hornady brass sucks, but what do I know...

KW

 

[dellet]

This data is from the Hodgdon site for CFEBLK. I don't have any complaints with CFEBLK so far. It is almost identical to Accurate 1680, which has long been the standard for BLK, it is available which is a HUGE plus, and it only costs $38/lb at my local Sportsman's Wharehouse. I have 5 lbs. of it and it works ok so far. I'm not shooting subsonic though, I'm shooting 110gr and 120gr Barnes TTSX, using their load data as a reference. Aside from any load data, I think EVERYONE needs to test fps in their own rifle. There are too many variances.

Twist: 1:8.000"
Barrel Length: 16.000"
Trim Length: 1.363"
Bullet: 208 GR. HDY A-MAX
Diameter: 0.308"
Case: Hornady
Primer: Remington 7 1/2, Small Rifle Magnum
COL: 2.260"
Max load: 11.6 gr

FWIW, I would check your seating depth on the light primer strikes. Quite honestly I think the Hornady brass sucks, but what do I know...

KW

In post 17 I shared two targets. The first with vertical stringing and horizontal scattered from hell to breakfast was Hodgdons exact data you posted using two different rifles.

The second target data is listed. Basically just seated the bullet down until it was .020” into the powder. CFE like compression, you can do that easy with supers. You lose 100-150 fps compared to say 296/H110. It can be very accurate, but it’s velocity challenged in an already low velocity cartridge.

The other data and scattered group on the second target was typical of low density loads. Note the ES of 350 and SD of 135. Didn’t matter sub or super.

But the more you compress it, the tighter the groups and numbers get. It never loses the qualities of loud, Smokey and dirty. If I want that I’ll shoot Blackpowder.

 

[Konocti's Wigwam]

In post 17 I shared two targets. The first with vertical stringing and horizontal scattered from hell to breakfast was Hodgdons exact data you posted using two different rifles.

Yes, I noted that. You had only .1 grain difference.

The second target data is listed. Basically just seated the bullet down until it was .020” into the powder. CFE like compression, you can do that easy with supers. You lose 100-150 fps compared to say 296/H110. It can be very accurate, but it’s velocity challenged in an already low velocity cartridge.

This is an interesting point. I haven't had enough time to get back to the range and gather data. As I have mentioned, I believe that everyone needs to test velocity for themsleves on their own firearms, even though the data is most likely reliable. I loaded up with data per the Hornady phone app for 300 AAC blackout. They had data to seat 2.210, but I was having a hard time seating to 2.235 as it was so compressed.

That is the one factor that could make a huge difference.

The other data and scattered group on the second target was typical of low density loads. Note the ES of 350 and SD of 135. Didn’t matter sub or super.

So, are you saying that by relaxing the load and moving the bullet out farther is what helped get those groups? I have rarely found my best groups at max load, so I tend to air for 0.5gr-1.0gr less.

But the more you compress it, the tighter the groups and numbers get. It never loses the qualities of loud, Smokey and dirty. If I want that I’ll shoot Blackpowder.

I can't run a suppressor, yet. Lots of regulation is under scrutiny. That's mainly why I haven't been interested in subsonic very much. I wish I could. However, it still doesn't discount 300bo or 8.6bo with supersonic.

In general I want a small light rifle to use for hunting. My 300bo is the smallest of all of them. It is also the least deadly. Oh, I do have a bunch of subsonics I will use for home defense which have 210 gr SMKs, but I can't hunt with those in California as they are lead. The next lightest is a 12" 6.5 Grendel. And finally the heaviest is my 8.6 blackouts.

 

[dellet]

Yes, I noted that. You had only .1 grain difference.



This is an interesting point. I haven't had enough time to get back to the range and gather data. As I have mentioned, I believe that everyone needs to test velocity for themsleves on their own firearms, even though the data is most likely reliable. I loaded up with data per the Hornady phone app for 300 AAC blackout. They had data to seat 2.210, but I was having a hard time seating to 2.235 as it was so compressed.

That is the one factor that could make a huge difference.



So, are you saying that by relaxing the load and moving the bullet out farther is what helped get those groups? I have rarely found my best groups at max load, so I tend to air for 0.5gr-1.0gr less.



I can't run a suppressor, yet. Lots of regulation is under scrutiny. That's mainly why I haven't been interested in subsonic very much. I wish I could. However, it still doesn't discount 300bo or 8.6bo with supersonic.

In general I want a small light rifle to use for hunting. My 300bo is the smallest of all of them. It is also the least deadly. Oh, I do have a bunch of subsonics I will use for home defense which have 210 gr SMKs, but I can't hunt with those in California as they are lead. The next lightest is a 12" 6.5 Grendel. And finally the heaviest is my 8.6 blackouts.

There is a lot there to sort out. Probably best is to link to where I tested the powder, and some others experiences with the same, more than 6 years ago. That way I’m not taxing my memory.

CFE 300 BLK first thoughts update 1/28/17 » 300BlkTalk

With CFE BLK a more dense load seems to lead to tighter groups and lower ES/SD numbers. Moving the bullet out creates the opposite. Less density, higher numbers. You’ll see that in my targets.

I use a drop tube for all my loading and a slow pour. This maximizes case capacity. In a small case like 300 Blackout, you can pick up more than a grain, or close to 5% more powder.

Suppressed ARs do not have to be dirty, or loud or Smokey. It takes careful load work up, a well tuned rifle for that load and being willing to spend the time to match the powder to the bullet weight.

It’s simple math when you look at the numbers generated with Quickload. If you have an 8 grain load that burns 100% in 7” of barrel, vs a 12 grain load that only burns 85%. One of those loads will leave 2+ grains of powder in your face and trigger group. One Will have less muzzle flash and less pressure pushing gas past the charging handle and out the ejection port. The faster powder will have less noise for the suppressor to mitigate.

The same applies to a suppressed bolt action. If you can’t hear the sound of your firing pin spring vibrating, if it doesn’t sound like a dry fire, your load sucks.

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

What CFE has going for it is that anyone can slap together an AR with all kinds of questionable components and put a load together that will cycle the action. I used it to prove a point. 110 grain bullets, full function, subsonic with carbine gas. The problem was it burned so dirty that the trigger group failed after about 6 shots.

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

Building a bolt action and using the same loud and dirty powders needed to cycle an AR is a recipe for disappointment.

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.