.300AAC problem too fast.

I've been working on a sub sonic load for my Blackout. I've tried 6 different loads all of which are supposed to be subs. I'm using the Lee 230 grain cast with powder coating. Accuracy doesn't seem to be a problem since I'm smashing clay birds at 100 yards. The problem that I'm having is that the velocities are too high! I'm using what they describe as absolute minimum loads. Average velocities are running between 1180 and 1250 fps. H110 so far has had the smallest spread. Any ideas on the wisdom of further minor reductions in loadings? So far, ejection has not been an issue. Yes, I am chronographing these loads.

You might have to work down some while watching out for squibs. At 1050 you should not get squibs but if something dramatically lowers more than expected you could end up with one.

Take a peek over at 300blktalk.com, there is a wealth of subsonic data over there.

less amounts of a faster powder.
or more of a too slow powder.
I'm assuming this is an AR so never mind the too little of a too fast powder, and focus on slowing the powder down.
4227 at 10 grs would be right about below the speed of sound.

It is an AR. The last powders that I tried were IMR 4198, IMR 4227, H110, Lil'gun and CFEBLK. I tried what they called minimum loads and all were too fast. Maybe .1 gr reductions? If no joy, the try again? I'll check out 300blktalk.com. Thanks

If you look at Hogdon's website for some of the powders you mention they do not list Minimum loads but Maximum loads. Subsonic loads are a bit different to load, you start high and work down.

A lot of data lists minimum loads in reference to high end supersonic load pressures. Subsonic load data is a whole different ballgame. I don't use H110 as I had other choices, but AA1680 is supposed to be the go to powder for subsonic (220-240) grain loads in the BO. I load somewhere in the 9-10 grain range with AA1680 and a NOE 247 whisper hollowpoint. Of the powders you listed, I would think that H4227 would be your best option. I know some load H110, but I don't have any and have not used any. 4198 may be a bit on the slow side. Not sure on CFE BLK.

If your pulling data out of a manual, you're probably not going to get minimum loads to be subsonic. The general rule is to work down in charge weight until you get in the velocity range you're looking for using an appropriate powder (usually not H110 it doesn't like to be downloaded) That puts you "OFF-BOOK" with your loads. IF you are not comfortable going off-book with your loads, then maybe subsonic is not something to delve into at the moment.

Brad

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Originally Posted by jimb16

It is an AR. The last powders that I tried were IMR 4198, IMR 4227, H110, Lil'gun and CFEBLK. I tried what they called minimum loads and all were too fast. Maybe .1 gr reductions? If no joy, the try again? I'll check out 300blktalk.com. Thanks

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You didn't say what gas system length you are using. In MY AR, I shoot the Lee 309-200-R subsonic with H4198, at below book loads. I has a pistol length gas system. I seriously doubt that H110 can be made to function because of that particular powder's characteristics. Also be aware that heavier bullets will be more easily made to functiom.

Edd

What length gas system and what length barrel? I have a 10.5" with pistol length gas system and so far all published sub loads I have tried stay sub but the same loads in my 16" pistol length gas upper almost all go above subsonic. If you have a longer barrel you may have to play with different powders and if your gas system is longer than pistol length you may have cycling issues with subsonic loads.

Its a 21 inch barrel, 1:8 twist carbine gas system. I load 7 TCU so I'm used to going "out of bounds". CFEBLK is supposed to be made for use in the 300BLK including subsonic loads. I'll continue working with that. AA1680 doesn't seem to be available around here. I'll see what I can do with IMR4227. I'll probably keep working a bit with H110 too, since it had the most consistent velocities and the lowest extreme spread. And as I said at the beginning, I'm working with a 230 gr. cast PC'd bullet.

Quote:

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Originally Posted by jimb16

Its a 21 inch barrel, 1:8 twist carbine gas system. I load 7 TCU so I'm used to going "out of bounds". CFEBLK is supposed to be made for use in the 300BLK including subsonic loads. I'll continue working with that. AA1680 doesn't seem to be available around here. I'll see what I can do with IMR4227. I'll probably keep working a bit with H110 too, since it had the most consistent velocities and the lowest extreme spread. And as I said at the beginning, I'm working with a 230 gr. cast PC'd bullet.

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That is going to be a tough one to run subsonic and still function reliably. If you do find a reliable subsonic load it should be very quite.

I had trouble getting subsonic out of H110 in a bolt Savage .300B, and second the recommendation for AA1680. I haven't been able to try it myself as my powder fund is low and every time I have $ and look for 1680 I can't find it.
BDGR

I'd work with the 4227.
I am thinking you can get close to 8grs with the carbine length tube.

Try around 7.0 grains of little gun

I have a Noveski AR 10.5" shooting the NOE 311-247 HP (weights 225-226 with the HP) with a YHM Suppressor and that load works great for me

below is a target of exact same load in a Ruger american (bolt gun) as well

Attachment 204505

and here is the lee 230 gr load in the 10.5" Noveski AR
At 744 FPS and a suppressor its spooky quiet

Attachment 204506

The reason I switched to the NOE 247 was I could never get a good crimp on the lee bullet where I wanted it

several times I had bullets end up being shoved in the case during trip in chamber during function testing so before I had a bad issue I switched molds

I run subsonic out of a Rem AAC rifle. Standard length barrel, h1680 and a 240 grain lead slug
It doesn't cycle on my 10.5 inch AR SBR. But I have a suppressor I am gonna try on it.

Try AA1680 and RL-7, they are very close in burn rate and give plenty of gas to cycle the AR and stay subsonic. I never had much luck with subs in my AR with W296/H110 but they did ok in my sons AR.