I have a bunch of 700x and 180g BT bullets. I also have 150g bullet mold. Anyone shooting subsonic in 300BLK with 700x. IT would be a 16" barrel. Suppressed, pistol length gas, hoping to make it run.
300 blackout subs
- Thread starter supercorndogs
- Start date
I don't want to say it's not possible because it is very possible. That said odds are good that you will have a ton of problems.
Powder shift is definitely a thing so making them function as reliable will be tough.
Plus the ratio of powder charge to velocity is not a 1:1 formula especially as you get into lighter weight bullets.
Out of a bolt action rifle it will be a lot easier to get it done but in a semi auto that is yet another barrier to overcome.
Basically my own testing shows that it might be possible but in a semi auto in regular field conditions it's not really worth it.
The lightest weight bullets I have been able to get reliable function out of are 190 grains. Any lighter and you get exponential problems. In my opinion 190 is about the line and even there the choice of powders is much more narrow.
Powder shift is definitely a thing so making them function as reliable will be tough.
Plus the ratio of powder charge to velocity is not a 1:1 formula especially as you get into lighter weight bullets.
Out of a bolt action rifle it will be a lot easier to get it done but in a semi auto that is yet another barrier to overcome.
Basically my own testing shows that it might be possible but in a semi auto in regular field conditions it's not really worth it.
The lightest weight bullets I have been able to get reliable function out of are 190 grains. Any lighter and you get exponential problems. In my opinion 190 is about the line and even there the choice of powders is much more narrow.
I do a LOT of off label use of powders for the 300 Blackout. Designed and licensed 300 Blackout specific bullets.
I spend hours researching thermal expansion data, burn rates and pressures to get the perfect powder for the project. I choose the powder to give the velocity I want with the lowest possible muzzle pressure. This results in a lot less gas and muzzle pressure your silencer has to mitigate. Powder selection is HUGE when you want the quietest possible load.
I have a load that is as quiet as a slingshot slinging 265g bullets. The 265g is a bullet I designed then licensed. It is perfectly stable in an 8 twist or faster at subsonic velocities. It is also stable in a 10 twist with a velocity above 1,100 fps.
Shoot me a message and I will give you my number so we can talk.
I spend hours researching thermal expansion data, burn rates and pressures to get the perfect powder for the project. I choose the powder to give the velocity I want with the lowest possible muzzle pressure. This results in a lot less gas and muzzle pressure your silencer has to mitigate. Powder selection is HUGE when you want the quietest possible load.
I have a load that is as quiet as a slingshot slinging 265g bullets. The 265g is a bullet I designed then licensed. It is perfectly stable in an 8 twist or faster at subsonic velocities. It is also stable in a 10 twist with a velocity above 1,100 fps.
Shoot me a message and I will give you my number so we can talk.
Pretty interesting thought. Our own little custom XP-100 has always had a serious issue with extreme velocity spread’s running close to 100 FPS. When this amounts to just under 10% of the velocity, hitting steel rams regularly at 200 meters becomes just one little bit harder.
So, in the vane of shooting subsonic, I thought I would try a little test. I purchased a box of Subsonic 300 Blk and fired it along side my handloads using our Labradar to see if my handloads were the issues.
My handloads were a bit fast, running an at an average of 1236FPS (200 grain SMK in front of 10.6 WW296 started with a CCI 450 primer. ). I had thought considering the combination that it might run fast but this was the most accurate combination found. The extreme spread was a massive 98 FPS with an SD of 32.5. The entire string was mired by the second shot our of the XP but the first shot across the chrono being 1178 FPS, and the third being 1276. Take away these two shots and the last five shots showed a spread of only 46FPS.
Not that any of this is really good and that’s why the Custom XP in 7TCU is the money gun and why the 300 is kind of a ”wonder why I spent this much money gun?”
Now the shocker. Factory match loads, same gun, same time, same Labradar.
Extreme spread, 93 FPS, SD 35.5. True, the loads were subsonic with a average FPS of 960.
For particulars, the XP has a 15 inch Shilen barrel 1x7 twist (actually probably a 14.98 inch barrel to remain legal in IHMSA) a Del Taylor Trigger set at 2.5 onces, an HS Precision Stock and a 7X Burris Handgun scope with a dot reticle. Weight is just below six pounds.
So, I keep seeing where folks are getting great accuracy from Blackout/Whisper/300/221 firearms, but for me, its the TCU. It shoots, it takes down rams and I have shot more 40x40 IHMSA scores with it than all the other handguns I own combined. And it is the one firearm I own that I have told my family that if I go first, it is never to be sold.
So, in the vane of shooting subsonic, I thought I would try a little test. I purchased a box of Subsonic 300 Blk and fired it along side my handloads using our Labradar to see if my handloads were the issues.
My handloads were a bit fast, running an at an average of 1236FPS (200 grain SMK in front of 10.6 WW296 started with a CCI 450 primer. ). I had thought considering the combination that it might run fast but this was the most accurate combination found. The extreme spread was a massive 98 FPS with an SD of 32.5. The entire string was mired by the second shot our of the XP but the first shot across the chrono being 1178 FPS, and the third being 1276. Take away these two shots and the last five shots showed a spread of only 46FPS.
Not that any of this is really good and that’s why the Custom XP in 7TCU is the money gun and why the 300 is kind of a ”wonder why I spent this much money gun?”
Now the shocker. Factory match loads, same gun, same time, same Labradar.
Extreme spread, 93 FPS, SD 35.5. True, the loads were subsonic with a average FPS of 960.
For particulars, the XP has a 15 inch Shilen barrel 1x7 twist (actually probably a 14.98 inch barrel to remain legal in IHMSA) a Del Taylor Trigger set at 2.5 onces, an HS Precision Stock and a 7X Burris Handgun scope with a dot reticle. Weight is just below six pounds.
So, I keep seeing where folks are getting great accuracy from Blackout/Whisper/300/221 firearms, but for me, its the TCU. It shoots, it takes down rams and I have shot more 40x40 IHMSA scores with it than all the other handguns I own combined. And it is the one firearm I own that I have told my family that if I go first, it is never to be sold.
The biggest detriment to an accurate 300 Blackout is Lake City brass. It is what everyone wants but it is the most inconsistent brass on the planet. I was getting 100+ fps spreads that I could duplicate. Started using quality brass and I consistently get single digit SDs.
I was looking at 100 dollar barrels and sub 300 dollar uppers. I was just looking for something quiet to bang away on for cheap.
What about the Lee mold that makes a 230g bullet, can I powder coat them and shoo them through a suppressor?
The Lee mold may work, but I believe they are a bit skinnier than I like em...
Spend a little more and get a good mold. Cleaning lead out of the bore from an undersized bullet SUCKS. Noe makes some excellent blackout molds. Run them fat, likely .310 sized after coating. Thats worked well in every 300blk ive used it in. Good powder coating will hold up being fired for sure. Make one, hammer it flat and see what your coating does.
Better yet, fire and recover a few to see what its doing. I've seen poor coatings fail and flake off with a thumb nail before ever even going in the brass.Don't do that and you should be golden.
A Lyman m die will let you expand the case to not fuck up your nice fat bullet and pretty coating.
If you're going for quiet plinking, as was said above, powder choice matters. Very good info there. A lighter bullet in the 125 or 150 or less range will use less powder, make less noise, and allow use of trail boss and tin star too. The little xtp bullet is sweet in this role if you can swing jacketed. Brass quality matters too as was said. You will likely have to work, lots of testing to get real good accuracy, say better than 3 moa in most cases. It can be done though.
All that said, from an AR, non manual cycle and or non custom gas system, you're using the wrong tool, though it can be done. Single shot etc will be best of you aren't gonna throw much cash at it I think. Better bang for the buck etc.
Spend a little more and get a good mold. Cleaning lead out of the bore from an undersized bullet SUCKS. Noe makes some excellent blackout molds. Run them fat, likely .310 sized after coating. Thats worked well in every 300blk ive used it in. Good powder coating will hold up being fired for sure. Make one, hammer it flat and see what your coating does.
Better yet, fire and recover a few to see what its doing. I've seen poor coatings fail and flake off with a thumb nail before ever even going in the brass.Don't do that and you should be golden.
A Lyman m die will let you expand the case to not fuck up your nice fat bullet and pretty coating.
If you're going for quiet plinking, as was said above, powder choice matters. Very good info there. A lighter bullet in the 125 or 150 or less range will use less powder, make less noise, and allow use of trail boss and tin star too. The little xtp bullet is sweet in this role if you can swing jacketed. Brass quality matters too as was said. You will likely have to work, lots of testing to get real good accuracy, say better than 3 moa in most cases. It can be done though.
All that said, from an AR, non manual cycle and or non custom gas system, you're using the wrong tool, though it can be done. Single shot etc will be best of you aren't gonna throw much cash at it I think. Better bang for the buck etc.
I have used a bunch of different brass successfully. Brand isn’t as important as making sure they are the same.
Currently I am using MagTech brass. It is very consistent brass. I also match prep ALL my brass. Uniform and debur the flash holes and I nspect them visually using a scope. I used to sort the bullets by weight as well as by bearing surface length.
A buddy was connecting at over 600 yards shooting subs out of my 6” 300 Blackout. 99.9% of everything I do is with subsonics. I spend hours researching powder specs and using programs like QuickLoad to find the powder best suited fit the barrel length. I match powder to the barrel length so the subs are quieter with a silencer. I rarely use published data anymore for anything subsonic related.
Most people cut the boat tail out or shorten that mold. Powder coating does help but some powders are awful with cast, even if coated. That particular bullet never really worked well. I have owned three of their molds trying to get it to work, never could.
If I were to get back into casting I would buy a 245g mold from Accurate. They have been proven for over a decade now.
There is also a 265g cast bullet available from ACME Bullet Company. I designed it so if you have any questions ask. The biggest question, yes it is stable in an 8 twist or fact at subsonic velocities. Stability has to do with length more than anything and cast bullets are short and stubby compared to jacketed.
For a single shot forget 296, it isn't that great as a sub powder anyways.
What barrel length? I have done a LOT of testing on single shot guns with SHORT barrels. I use Red Dot for 99% of my shorter barrel heavy loads. VV3N38 also works well on single shot shorter barrels with heavy bullets.
I will gladly help anyone I can with specialized loads for non semi auto. I am shooting subs past 500 yards regularly.
When you load lighter loads with certain powders they do not seal properly and cause staining on the case mouth. Using faster powders will help seal the case to the chamber.
