300 blk case prep from .223 cases

[Marksman829]

This might sound like a dumb question but am I supposed to use RESIZED .223 brass prior to cutting it at the shoulder, or can I just cut a case that's been fired but not resized yet?

I know I obviously have to resize it with a 300 blk die once the shoulders been cut off, but I wasn't sure if the .223 case needed to be resized prior to being cut?

Hope someone who makes their own 300 blk brass can help me out, thank you in advance!

[fast54vw]

I just cut them, then form in the 300 die, trim and load

[Marksman829]

Cool thank you! That's what I figured but can never be too careful... thanks again

[ar15barrels]

Cut them slightly long, form them and then trim to final length.

[Marksman829]

Thx for the advice I'll give it a try

[webcruzzer]

You really should anneal before resizing. It will help minimize splitting shoulders during the reform.

[Marksman829]

You really should anneal before resizing. It will help minimize splitting shoulders during the reform.

I was reading something on that... seems like a real PITA if I had to do that for each case lol. How long do you need to hit each case? Do you just use a torch?

[webcruzzer]

I made a diy case annealer. There are alot of plans online to make one. My cost was just over $100. I had to buy alot of parts. Plus I bought a few proximity sensors for feeding and counting. I put a video on FB. It's towards the bottom of the comments.

https://docs.google.com/document/d/1bb_cm10J8urCM2PtKql8VyHtGlovTeI3RnAj7xa0eX0/mobilebasic

https://m.facebook.com/groups/671545566281534?view=permalink&id=1171928396243246

[Marksman829]

Cool thank you!

[stand125]

Has anyone ever had a split neck from sizing 223 to 300 blk. It barely sizes the neck at all since it is a 30cal bullet.

[2shotjoe]

I cut at the start of the bottle neck, I get plenty of brass to trim after resizing.

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[2shotjoe]

Has anyone ever had a split neck from sizing 223 to 300 blk. It barely sizes the neck at all since it is a 30cal bullet.

Yes, bad brass. Just junk it since 223 is easy to come by.

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[cg&p]

I just cut down and sized/formed about 200 cases from 223 last night and didn't have one case split. I used a lee precision size die to form the cases. No annealing. just FYI for what it's worth...

[divingin]

Has anyone ever had a split neck from sizing 223 to 300 blk. It barely sizes the neck at all since it is a 30cal bullet.

My experience as well. Not forming much of a shoulder at all, so not really a whole lot of brass movement going on. IMO, annealing before forming is a waste of time. Afterward may be a different story.

[mjmagee67]

Cut them slightly long, form them and then trim to final length.

Yea...this.