An AR in .300 AAC Built Specifically For Heavy Sub-sonic Boolits?

[klcarroll]

In order to stave off boredom, I have decided that I need to build a .300 AAC AR specifically for heavy, sub-sonic, cast boolits.

In searching this site, I have noted that there are a number of people here who are working with this caliber; ……And I would like to hear their opinion of an idea that has occurred to me.

I have noted that CMMG makes a 16” .300 AAC barrel that will allow either a “pistol length” or “carbine length” gas system to be fitted: …..And I am thinking that the “pistol length” gas system would make it easier to achieve reliable cycling with sub-sonic loads. (….Possibly even allowing the use of powders like Unique.)

Thoughts? …..Opinions?? ….Criticism???


Kent

[Artful]

Pistol length does tap the gas from the barrel earlier and when the pressure is higher so works well with subsonic loadings. Only problem with pistol position is that it can overgas with supersonic loadings with slower burning powders dumping gas back into the action much more violently than desired.

[DCM]

Adjustable piston drive system maybe??

[Artful]

You can just put in an adjustable gas block
or you can go as far as this two gas block (pistol and carbine)
with adjustable gas tube from carbine back...
http://img.photobucket.com/albums/v355/rowdyfisk/FAL/bothports.jpg (http://smg.photobucket.com/user/rowdyfisk/media/FAL/bothports.jpg.html)

[fullofdays]

I am building a 9 inch SBR in 300 AAC. DI gas system all the way. It will cycle subsonic and supersonic suppressed and unsuppressed all day long

Sent from my SCH-I510 using Tapatalk 2

[xacex]

I have both a pistol, and a rifle. The rifle is carbine gas, and pistol is pistol gas. From what I have learned with the two is any listed load from powder company's, or AAC will work with both. However, if you intend to use only subs, and experiment with slower powders you may want to try the pistol gas on a carbine. I would hate to be pigeon holed into the adjustable gas block like the 300 fireball guys with the pistol gas however, and myself will stick with what is recommended for 300 blackout.
I love this round, but understand it has it's limit's. If given a choice of gas systems I have chosen the factory recommended gas knowing I can use any slower powder, and It may function as a bolt action, but will still work for subsonic. If you are just into it for the experiment, go for the pistol gas, and an adjustable gas block if you intend on shooting supers in the future. I enjoy both! I think anyway you go you will enjoy the gun!
xacex

[Tank56]

I like that set up that Artful shows. If you are going to use a suppresser (silencer) go to the pistol length gas tube. You can always get an adjustable gas block later if needed, or go to a custom gas system.
What I have found with faster pistol powders is that you can get very good accuracy from them but they have a very small range of weights. For example: 5.8 grain of Unique and my 200 grain boolits tumble, 6.3 grains of Unique with the same boolit and the primers start to flatten. This is with my AR, others may vary.
With a suppressor Unique is very quiet.
(IMR or H) 4227 and blue dot work very well for both sub-sonic and super-sonic loads for me.

[klcarroll]

I really appreciate all the comments.

Since my primary objective is launching heavy cast stuff at subsonic velocities, I think I will try the "pistol length" gas system on a 16" tube.

Here in Illinois, suppressors are forbidden: (......What do you expect from the new East Germany?) .....And it is just not very easy to find a place to plink or "rat shoot" with a rifle because there is always someone who will call the "County Mounties" if they hear a high-power sonic signature. (...And with our Governor trying to ban almost everything that feeds from a magazine, "discretion" has become VERY important!)

......So I am looking for a load/weapon configuration that will be as quiet as possible while still functioning the action.

If someone has some favorite "quiet" cast boolit loads that still function the action, I would like to hear about them.

Kent

[Moonie]

I agree, for sub only use pistol length gas. My son and I have 1 each, we shoot both sub and supersonic so we opted for carbine length. You should be able to shoot faster powders than I can. I find H110/296 sub loads iffy in a carbine length but should be just fine for a pistol length gas.

Come to think of it I might have to build another with pistol length for subs only. Do be careful, AR's are addictive.

[klcarroll]

...........Do be careful, AR's are addictive.


TOO LATE!!! .........This one will be my forth!


(.....And on a serious note, ....Thanks for your information!!!)


Kent

[Moonie]

TOO LATE!!! .........This one will be my forth!


(.....And on a serious note, ....Thanks for your information!!!)


Kent

Interestingly enough I have 2 and neither is 5.56/.223...

[xacex]

I'm looking at building #7. I tried 4 5.56 builds, and just didn't like the round. Sold those, and did 2 blackout's. One pistol, and a rifle with a carbine length gas system. I haven't been happier! Now I am putting together parts for a 50 Beowulf. Thought about the SOCOM, but bullets cost more, and I have got to get a "50" before civilians aren't allowed to purchase them anymore. Just waiting on a barrel. Wish me luck, parts have been slow to come lately.
Since I have got into AR's the bolt actions, and other semi's have only been only pulled out three or four times this year. I have started selling off unused firearms to feed the addiction.
xacex

[jbaldwin]

This is exactly what I'm working on too. I've been intrigued with tinkering with an Adams Arms piston kit I came into on a trade. It's a carbine length kit, so I began with a Green Mountain barrel blank and built an upper. As expected a good clean cycle of a cast Lee TL309-230 is the problem I'm working on trying to solve now. Adjusting loads has got me ALMOST there, so I'm on the brink of getting it to work. I've got to think there is probably a similar "nut-case" like me somewhere doing the same thing: 300 blk, piston, subsonic, heavy cast lead, tumble lubed bullets. Anyone? . . . . Anyone? . . . . . . . Anyone? . . . .