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Old April 9, 2013, 10:19 AM   #1
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Cartridge Resizing .223 to 300 Blackout/300 Whisper

Getting in to the 300 Blackout/300 Whisper (300 B/W) on my AR-15 platform and I was wondering about converting a barrel of 5.56 once fired to the 300 B/W so I can have more fun. Also, with all the crap coming out of Washington, I want to put in a store of brass and 5.56 is the most prevalent once-fired brass available.

I expect that it takes four procedures, anneal, trim, form, and trim to length. I assume this because the 7.62mm bullets are a lot longer than are the .223/5.56 bullets.

I have also read where the 300 Whisper for the TC was originally made from .221 brass. Since one of the selling points of the 300 Blackout is that the standard BCG for the 5.56mm is usable without modification, I assume that I can use the 5.56 brass as easily.
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Old April 9, 2013, 11:41 AM   #2
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Looks like you have the process down.

Two things.

As I re-formed my 'junk' brass collected over the years. I don't/didn't anneal right off. It was just junk brass being reclaimed. I think it would be a good thing to do, I just never did it. I do anneal about every 5th loading (most all bottle necked brass). A 'chop saw', like one from Harbor Freight, makes the cuts quickly.

Second item, I understand that some are having problems with 'thick' body brass and are needing to ream the new necks. All of my re-formed brass worked fine. It was Lake City (LC) with a few Twin Cities (TW). My advise is to look at the neck thickness. Your brass could need thinning.

I only loaded super sonics and was getting 25 and more loads from a single case. Seating depths have a greater effect with the BlackOut than I have encountered with other loads. Keep this in mind.
It is a fun round and does very well in its nitch. Wish I hadn't sold mine

Load safe and have fun,

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Old April 9, 2013, 11:57 AM   #3
Join Date: October 20, 2012
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Re: Cartridge Resizing .223 to 300 Blackout/300 Whisper

My process for going from 223 to 300blk goes like this

1) cut case at neck of 223 (leaving next to no neck left) using a mini chop saw from harbor freight (30 bucks)

2) lube and size/deprime bases

3) trim to size using trimmer of choice (I use rcbs one)

After that its just normal prime, Bell mouth, seat bullet, crimp of desired.

I haven't annealed myself but know people who do. I do my processing in batches so do all cutting one night, then sizing the next, ect.
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Old April 9, 2013, 12:01 PM   #4
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There is a copy cat afoot. Is it me or 'velillen'?


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Old April 9, 2013, 12:06 PM   #5
Join Date: October 20, 2012
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Re: Cartridge Resizing .223 to 300 Blackout/300 Whisper

Originally Posted by oldpapps View Post
There is a copy cat afoot. Is it me or 'velillen'?


Lol I'm sure there are tons of copy cats! I know I got the process off another forum and it just worked for me! There's more than one way to skin a cat, but this method fits my reloading style the best. I'm a do 1 step at a time in large batches type guy vs doing everything at once in just what ya need
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Old April 9, 2013, 12:34 PM   #6
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Oh, darn!
I was thinking of charging for the use of the wheel. Guess I didn't invent that either.

We all learn from one another, some times only a little and other times a great deal.

I would have to say that the only independent contribution to the .300 AAC BlackOut is my work using Olin WW630 powder. And that is only because few have ever seen any of it and I have several pounds that I wanted to make use of. It like making a right handed locking hillside washer nut. Who cares?

Forums like this one are the great resource of mankind. Information is exchanged in second that would have taken months if not years to disseminate a few years ago. That's good. The bad slice is not everything is valid. And you and I concurring on the general process of the conversion of brass is only one more plus in the process. I never take one source as 'Gospel', I don't even trust my data until I have checked it, twice.

Enjoy, learn, live well,

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Old April 9, 2013, 07:49 PM   #7
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Something I did when doing the initial resize was to run it through the resizing die twice, one cycle, turn the case 1/3 to a 1/2 a turn and give it another pull. I found sometimes just doing it once didn't seem to set the shoulder back far enough, or just didn't get a good form on it and the bolt wouldn't close. But after the double resize, never a problem.
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Old April 9, 2013, 10:25 PM   #8
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same as velillen also. Made a jig for the chop saw and eventually got it down to where I don't even trim after sizing although I do check the trim.
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Old April 10, 2013, 12:02 PM   #9
A pause for the COZ
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I was going to buy one of those small chop saws from Harbor freight.
But I noticed I already had a full size chop saw.
Will it work?

Sure does, Made a quick Jig for it.
The only thing I have changes, I put a 7 inch blade I had with a fine tooth profile.

Knocks out a few hundred in no time at all.

Just use a peice of scrap with a notch cut to hold down the brass while cutting. ( not putting my hands any where near that spinning stuff)

Works good.
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Old April 13, 2013, 10:50 PM   #10
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I just started loading 300 BLK also I made my first batch from some reclaimed 223/556 I got from one of the public ranges. I bought a 6" cutoff saw from Harbor Freight for $49.99 made a jig with a piece of 2x2. My process is similar it goes like this.
  1. Cut 223/556 brass right at the shoulder.
  2. Chamer & Deburr
  3. Lube cases.
  4. Deprime, resize.
  5. Trim to proper length.
  6. Chamer & Deburr Again
  7. Prime
  8. Charge
  9. Seat Bullet
  10. Wonder why I didnt buy some already made, oh yea bcause 300 BLK is has hard to find has hen's teeth right
“The problem with socialism is that you eventually run out of other people's money.”

-Margaret Thatcher-
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300 blackout , 300 whisper , blackout , resize , whisper

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