Cutting .223 brass?

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Rusty Shackelford
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Cutting .223 brass?

Post by Rusty Shackelford » Mon Dec 10, 2018 2:31 pm

I've been exploring the web for info on cutting 223 brass to make .300blk and I found minimum measurements anywhere form 1.360" to 1.368". So, what's a good starting point?

Also, is it important to anneal the brass after re-forming? No one mentions it but it seems to me it might be necessary since that portion of the .223 case would probably not have been annealed before. There's a lot of work involved in cutting, trimming and resizing, I'd hate to do all that and have them split after only one or two reloadings.
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Re: Cutting .223 brass?

Post by SwampDog_13 » Mon Dec 10, 2018 2:51 pm

I would recommend getting a jig and then cutting down your .223/5.56 brass to right behind the shoulder or the trim to length for blackout(1.358-1.368"), nothing needs to be exact here it'll just change how much final trimming you have to do. Remember when you reform the brass into blackout it will grow and then need to be trimmed down to your desired trim to length.

I don't make my own blackout brass and some more knowledgeable than I may disagree but I wouldn't anneal until after fireforming the brass just to save a step. It certainly wouldn't hurt anything if you annealed right out of the gate though.

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Re: Cutting .223 brass?

Post by golfindia » Mon Dec 10, 2018 2:58 pm

I don't anneal them. I don't have an annealing setup, so It's easier to just make new brass.

Never had a split neck on a 300blk.

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Re: Cutting .223 brass?

Post by Jcalloway » Sun Jan 06, 2019 5:06 am

I cut all of mine to 1.365 and then when I size them they grow about .010. I then final trim to 1.360 and they are good to go. I haven’t anealed any brass yet, but I haven’t had problems either.

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