Is .223 or 5.56 better for making 300 blackout cases?

For the most part both cases are exactly the same but for the head stamp. I would use the brass your rifle likes best. It will probably perform just as well when the neck is expanded as when it was still used for .223/5.56mm ammo.

I don't know if that's a good reason but it's as good as any other if you don't like removing the crimps.

BUT, if you like 5.56 brass you can always buy new Lake City Match brass which would have no crimp in the crimp.

One fired 5.56 brass is readily available free or cheaper than .223. Removing the primer crimp isn't a major issue. It's a one time operation and all you need is a $10 primer pocket reamer.

lharrell79 said:

Is one better than the other for cutting and sizing your own 300 Blackout cases? Is one case able to handle higher pressures?

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Before you start this, you need to look at page 93 of the latest American Rifleman. The cartridge, whether labeled Whisper or Blackout, is based on opening up the neck of the .221 Fireball, which is going to end up thinning the walls of the case neck. Cutting down a .223 to length then necking it down is going end up with thicker neck walls, which could get you in trouble with finished cartridges that won't chamber, if you are lucky. If you are not lucky, the rounds may chamber but the oversize neck will run the pressures way up (see the comments on chambers and throat dimensions in the rest of this article).
I tried being a wise guy years ago by cutting down .30-06 brass to make 8x57 cases for my cousin's Mauser 98 sporter: the finished rounds worked in my wartime military rifle, but wouldn't chamber in his tighter pre-war rifle. So much for my reputation as a reloading expert...
I think the savings in using .223 or 5.56 brass are going to be offset by needing to neck-turn every converted case to get the correct neck dimensions. Of course, it's your gun, so you can take your chances...
IMHO

Id choose witch ever you can get the most of, but i have heard lc brass has a higher case capacity compared to other similar brass

Edarnold said:

I think the savings in using .223 or 5.56 brass are going to be offset by needing to neck-turn every converted case to get the correct neck dimensions. Of course, it's your gun, so you can take your chances...
IMHO

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Have you priced 221 Remington Fireball lately? Even if you neck turned reformed 223 Remington cases, it would still be a substantial savings over 221 Remington Fireball.

221 Remington Fireball cases are too dear for me to use in anything other than my 221 Remington rifles.

I have formed 1500 300 BLK cases from 223 Remington cases and neck turning has not been needed, at least with the cases that I used (new and once fired R-P 223 Remington cases). The outside diameter of the case mouth of formed and sized cases is the same between 300 BLK cases and reformed 223 Remington cases.

Maybe other brands might be different.

Either 223 Remington cases or 5.56 NATO cases could be used to form 300 BLK cases.

(P.S. I did read the "American Rifleman" article).

I read that the 300 Blackout was designed to use a cutdown 223 and had allowances for the thicker neck.

I am a master typist, my Kindle fire goes out of its way to make me look bad.

joustin said:

I read that the 300 Blackout was designed to use a cutdown 223 and had allowances for the thicker neck.

I am a master typist, my Kindle fire goes out of its way to make me look bad.

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Don't know what the source was for what you read; the Rifleman article quotes the people that designed the cartridges. Who you going to believe?
IMHO

I've researched the making of blkout cases, and I've never seen anyone use 221 or anything else other than 223/5.56. There must be lots of people doing it wrong. I've also casually noticed a seller of blkout cases trying to source LC 5.56 brass by the truckload on this very forum.

lharrell79 said:

Do you have a link to the article?

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The article is in the printed magazine. I could not find a link to it online. It maybe in an NRA members only area.

I am still old fashion and like "touchy-feely" magazines.

www.americanrifleman.org/ArticlePage.aspx?id=1368&cid=31 isn't the article in question is it? it's from 2009 though soo...

An old friend of mine is a commercial ammo manufacturer. .300 Blackout is one of his specialies. He cuts down .223 or 5.56 cases, and doesn't do any neck-turning. So far, his ammo has performed just great with no blow-ups. With due deference to the American Rifleman article, if I were forming .300 Blackout brass, I'd cut .4" off of .223/5.56 brass and NOT worry about the brass thickness at the neck. Just a wild guess, but I'd opine that 99.999999% of folks making .300 Blackout brass from .223/5.56 brass don't turn the necks.

Look at the SAAMI drawings and measure the neck. The article I read was from one of the people that developed the round, I think they gave more room around the neck over the Whisper that didn't have as much room for thicker brass. I will try to find it tonight.

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I've made 2 or 3 thousand cases made from both commercial and military brass and found little if any difference from the factory 300 BLK cases. You could make them from 17 Rem Fireball as well but it would mean an extra expander ball. I made my cases by running the 223/5.56 brass thru a file and trim die and cut off the excess with a sawsall,used the file and trim die to clean up the clean up the length.