Questions Reloading sub-sonic 300 Blackout

[Spacehog 2,218]

I am looking at an AAC rifle in .300 Blackout and just finished my trust paperwork for an AAC can that I can use on my .308s and .223s. The appeal of the 300 Blackout for me is the ability to load subsonics and get really quiet. My questions are for those who are reloading subsonics. What are you using ( i.e. powder, bullet weights, etc), that will still cycle the action. Hornady's reloading manual singles out H1680 in this regard. Also I know that the .300 black out is basically a shortened .223 that is slightly necked down to accept a .30 cal bullet. Will the .300 dies properly neck down the .223 brass if it is trimmed to proper length or is a special step required for that. I have plenty of .223/5.56 brass that I could begin reloading with. Any suggestions are greatly appreciated.

[gunfun 3,931]

I suggest you PM member Dolomite Supafly.

 

He knows a lot about the subject.

[Spacehog 2,218]

Will do. Appreciate it GunFun.

[filthygovemploye 64]

google what you are lookin for

 

i am castin lee 230 gr blk boolits.

 

300blk forum says either 11.5 or 10.5 of 1680 or h110 respectively

[gunfun 3,931]

I've heard mixed things about that mold. Lots of people think the boattail was a bad idea for cast. How has it worked out for you?

 

I've shot one loaded from the NEI mold, and have been hooked on the idea ever since.

[netpackrat 566]

There is a guy who makes a jig that allows you to trim .223 cases for forming very rapidly using a harbor fright mini chop saw. He's on the gunco.net forum under the name "vz58" and other places I think also. He made me a shorter version of that jig for making 7.62x25 out of .223 and it works very well.

[gunfun 3,931]

Those looked pretty easy to make. There are a couple youtube videos on the topic.

 

I think using a lee quick trim for the precise trim and modding it for use with a drill on a progressive press would be very efficient.

[FORKLIFT352 63]

Harbor Freight mini saw

JB weld ( to form with 223 brass)(oil the brass first)

Then cut just below neck.

Resize

Trim

[gunfun 3,931]

That is a cleaner method.

 

Praise will be given to the first person to devise a good way of connecting a drill to a Lee quick trim cutter.

[RedChallenger 149]

There is a guy on the Blackout forum that I got a jig from that works great. It's designed to work with the HF cutoff saw. I am shooting my reloads through a 10.5 barrel, pistol length gas tube, and AAC 762-SDN-6.

I'm reloading using 220gr Sierra BT and 10gr of IMR 4227.

Edited September 1, 2013 by RedChallenger

[Spacehog 2,218]

Thanks Red. After cutting down the brass and resizing to 300 BLK have you seen any issues with neck strength on the new cartridge? I have read that you may only get 1-2 reloads on reformed brass due to the section of the brass that forms the new neck not being annealed. I am not sure this makes sense since many commercial cartridges do not have annealed necks like military brass, and I still get 4-5 reloads out of them easily. Also thanks for the powder recommendation. It doesn't look like I am going to get my hands on AA1680 anytime soon.

 

Also nice to see the suppressor you are using. That is the model I am getting.

Edited September 5, 2013 by Spacehog

[XD45 7,124]

One possible explanation for case failures is work hardening of the brass during the necking down process. It's always a good idea to anneal after necking down.

[gunfun 3,931]

Re: annealing- ditto to the above questions.

 

Another thought. I know the subsonic loads are often comparable in pressure and powder charges to 45 ACP. Is annealing really needed for such low pressure rounds? Or maybe just annealing after forming down the first time.

 

It looks fairly time consuming without an expensive rotary annealing rig.