Cutting .223 / 5.56 brass for .300 AAC

[NavyVet1959]

Well, now that my dies have finally come in, I decided to experiment around with forming some .300 AAC brass from .223 / 5.56. I had a piece of brass with a bent neck, so I started with it and just my Wilson case trimmer to see how long it would take and to get the first piece of brass to the right length to use it as a pattern for subsequent pieces.

It took awhile and would have definitely been quicker if I had the mounting stand instead of just having it loosely sitting on the edge of the table, but it did work. When I got it to the specified length, I then ran it through the dies and it did not have a problem (even though I forgot to lube the case). I then ran it through the case trimmer again to trim down any length it had gained by resizing.

Since that looked good, I decided to try a couple of options to see how well they might do to cut reduce the amount of trimming was necessary (i.e. rough cuts). First attempt was with a piece of 5.56 crimped blank brass that I had picked up from an Army firing range a year or so ago. I used a bench grinder to trim the crimped portion off and noticed rather quickly that it got rather warm. I stopped after just the crimped mouth was ground off, but it was definitely warm enough that I didn't want to continue holding it without gloves.

I then broke out my wet tile saw to see how it worked on brass. I just fed the brass though by hand along the shoulder line and it worked out pretty good. It wasn't perfectly perpendicular since I was just freehanding it, but it did work and considering how easy it went through, I doubt that it damaged the blade. The next cartridge that I tried also worked out easily, but upon further examination, it turned out that it was steel instead of brass.

I don't know if this is better than the Harbor Freight 2" chop saw, but it seems to work well and I didn't end up with yet another single use tool in my shop.

[NavyVet1959]

Tried a couple of loads today to see if they would cycle the action on the AR. Using the 230 gr Lee mold. Tried 6.1 gr and 6.9 gr of Red Dot with pistol primers. Primers flattened, but brass would not eject. Tried 6.1 gr of Red Dot with rifle primer. Primer looked more normal, but still the brass did not eject.

Probably need to try a published load to verify that I didn't mix up something on the build and accidentally created a single-shot firearm.

[Artful]

You need a slower powder 5744 to 1680 is the range I use in my carbine tube AR, you can use faster powders with Pistol length AR gas tube...

http://www.300blktalk.com/forum/

[StratsMan]

Ditto on the fast rifle powder... 5744 and 1680 are about as common as hen's teeth these days, so you might try some magnum pistol powder with smaller boolits... 135 - 155 grain should be easy to find a recipe that uses 296 or 2400...

[NavyVet1959]

You need a slower powder 5744 to 1680 is the range I use in my carbine tube AR, you can use faster powders with Pistol length AR gas tube...

http://www.300blktalk.com/forum/

It's a 6-5/8" gas tube.

[wordsmith]

Artful and StratsMan are correct on the powders. AA 1680 or in the same ballpark will do the trick. The faster powders haven't given me good cycling performance in heavy subsonic AR's.

I've tried quite a few ways to cut 300 BLK brass, and ended up back at the 2" HF cut off saw. Does a great job with a nice clean edge that I use straight in the sizing die, no cleanup required. I made a jig by drilling a just barely larger than OFB hole in a small block of wood that I use in the built in clamp to hold the brass. I use another block to push on the brass neck while cutting the brass. I can probably cut about 350 / hr when I get in the groove.

My brass grows about 0.010" when sized, so I shoot for a rough cut length of 1.355" +/-, which gives me a clean trim on all pieces in my Giraud to 1.358".

[fcvan]

I cut down the brass using a Harbor Freight mini chop saw. Then I form, and then I trim/chamfer. It is working rather well for me.

[Moonie]

For that size boolit try AA1680 or RL-7, they will cycle the action. I've used H4895 but the SD was very high, about 100fps.