300 blackout

[Eastexasrick]

Making 300 blackout out of .556
I have a few .556 range brass. As this is the parent of the 300 Blackout, seems like the right thing to do. Lathe off the shoulder. reform, trim, done.

 

[usmcpmi]

What are you using to reform the neck/ shoulder with?

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[Eastexasrick]

A regular full length sizing die. As the shoulder is so slight, compared to most, I figured it could handle it.
I lube them with the lightest grade cutting oil and work slow to avoid case dents. The attached image, the ones on the right are unsized, left full length sized. I pre trim them to .01 over length before sizing. After pushing the shoulder back they are coming in at .007 over length. All of this is completely based upon SWAG engineering, but they appear to be good.

 

[usmcpmi]

How is the wall thickness of the neck?
Do you have to thin it out because it was the side wall?

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[usmcpmi]

And what is your cut length? Are you using a collet or a standard chuck in the lathe?

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[Eastexasrick]

How is the wall thickness of the neck?
Do you have to thin it out because it was the side wall?

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I wa gsoing to check that against a factory case, but I don't have one. Meeting with a member this coming weekend who has a few> I will check that then.

 

[usmcpmi]

The stock cases I have show .011

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[Eastexasrick]

And what is your cut length? Are you using a collet or a standard chuck in the lathe?

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I am cutting to 1.378. after pushing the shoulder back they are coming it at 1.375

 

[Eastexasrick]

The stock cases I have show .011

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Looking now. .012

 

[Eastexasrick]

I am using the regular 3 jaw chuck, I grab the last .50 of the case, no center, just spinning in the wind. A square carbide cut off tip at 45 degrees to the case.

As your factory case neck is .011 and these all mic to .012, what is your opinion? close enough or turn a .001 off?

 

[usmcpmi]

I think I would load a couple dummy rounds and see how they chamber.

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[FireInTheWire]

I miss my 300blk

 

[cav2108541]

Making 300 blackout out of .556
I have a few .556 range brass. As this is the parent of the 300 Blackout, seems like the right thing to do. Lathe off the shoulder. reform, trim, done.


View attachment 435129

I used to just cut them with a hacksaw, a little longer than required for the finished product, full length resize, trim to final length, ready to go. There are plenty of sources for factory brass today, why bother? Just having fun, or what? In the early 70s I used to cut the crimp off of fired military 5.56 blank brass and trim to correct length after resizing. When the necks eventually cracked, I also used to hacksaw them and resize for 9mm and shoot them some more. Did the same with 7.62x51 and turned them into 45ACP. As a young soldier I made about 300 bucks a month (married), so all that was necessary because brass was expensive and sometimes hard to come by. Not worth the trouble today.

 

[usmcpmi]

So Rick, now you have created a monster!
Dug out some 5.56 brass and went to the shop. Promptly cut down 5 cases. Back to the loading room and trimmed them down. Sized them with a little Royal Purple. Measured and loaded a dummy round. It specs out exactly to some factory loaded rounds.
But I have a hand trimmer...going to be too much work to do any quantity by hand.
Time for a new power trimmer!
Woo Hoo!

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[usmcpmi]

By the way, I measured the mouth of the case after I cut the cases off...mine were .0095. So your cases look to be heavier than mine.

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[Brojon]

gawds - I must have converted over 500 brass this way using a Harbor Freight small chop saw.
I highly suggest a Sheridan gauge to check your parameters.
This is important because the die can not form a clean shoulder and it won't headspace correctly.
I cut all my 223 brass right at the shoulder to case junction which gets you to spittin distance of proper length.
I form using a Hornady die. I used to use a Lee die but it wasn't good concentricity and I was having to turn 90 a give it another pull. Even then they might sit high in the gauge because the shoulder was frankly a little sloppy.
I trim mine to 1.358-1.360 length. Below 1.355 there can be issues.
The reason I suggest the sheridan gauge is it also tests web/rim height. The gauge has two levels and by no means should it be proud of the top.
I find a lot of PRC and some LC brass just won't work - biggest reason is they use thicker brass which results in a neck thickness that "bulges" when you seat a bullet.
Just my 2 centavos - worth less than 2 cents.

300 Blackout Ammunition Gauge

Choose between SLOTTED or NON-SLOTTED. AMMUNITION GAUGES are uniquely designed to check loaded ammunition, giving you the ability to check your factory ammunition or reloads against a spec chamber. The gauge is machined to the SAAMI minimum chamber spec for the 300BLK caliber. This allows…

sheridanengineering.com

 

[usmcpmi]

Just put 150 "modified" cases in the tumbler.

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[deemus]

Similar to Brojon above, I use the Harbor Freight tiny chopsaw. I also bought the jig that’s available in the interwebs. Makes it easier.

Cut it at the shoulder.

Resize using the Lee resizing die

Use the Lee case length trimmer to cut to length.

Debur in and out.

Load em up!

Done hundreds of them that way with not a single problem.

 

[db_tanker]

From experience just as deemus described but I used a Lyman case trim express. I was kind of worried since it seems to index off the shoulder but I was sizing in a Lee and no issues? I didn't go as far as checking wall thickness though and now I feel kind of foolish. I do know that I didn't wrinkle any cases I made (used either Winchester, WCC or LC headstamp for conversion).

The fixture I got was from ebay and I just wish they were able to be adjusted for the cut since there was a massive amount of trimming needed after forming?

D

 

[Eastexasrick]

Loaded and ready to go. Chamber just fine, no wrinkles. In answer to the question as to why, with all the brass available, because ….