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98's 300 Blackout wisdom.


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It would be a PITA to split that topic, etc., however...

I can post it again in this thread, and then the whole thread can be moved/pinned in the Reloading Section.  :thumbup:

The steps I take on this stuff is as follows.  It's also subject to change if I can find any other steps that will make other steps easier...

Steps for my 300BLK manufacture:

1.  AR-15s get the $hit shot out of them at the range.  All brass policed up.

2.  All AR-15 brass (.223 Rem and 5.56 NATO) goes into the tumbler once it gets home.

3.  Sort out Lake City 5.56 NATO brass - that's the only stuff I'll turn into Blackout ammo anymore. 

4.  Run the Lake City 5.56 brass through the mini chop saw.  I was cutting it right at the neck, but that leaves ALOT of trimming.  I've been cutting it a little further back now, so I have less final-trimming to do.  I'll get pics next time I chop a batch up.

5.  Chamfer those now-straight-walled cases heavily, with VLD chamfer bits - this is important later, and for the next step. 

6.  Run them through the tumbler for about 15 minutes, to clear out all the brass shavings from chopping them - don't let that stuff tear up your 300BLK dies.

7.  Pull from tumbler, shake 'em out, and lube 'em up on the pad (or whatever you use).  You can hit straight-walled 5.56 cases with some pretty heavy lube, and it won't hurt the brass.  Typically, if you use too much lube, you're gonna dent in the shoulders of brass that you're just resizing.  That's one sign of "too much lube."  You can run this stuff heavy and it won't hurt new-made BLK cases - you're forming a brand new shoulder, where there wasn't one before.  I've yet to have a problem on a heavy-lubed pad, and any shoulder issues when making new BLK brass.

8.  Run 'em through the sizer/deprimer.

9.  Leave the lube on there - don't sweat it.  There's still alot of steps to go here...

10.  Change dies in the press - Run them through the Swager now - get rid of those crazy Lake City primer crimps.  Be aggressive with them in this step, because the new Lake CIty primer crimping is a 4-Corner affair.  Lake CIty wants to make sure you never blow out a primer in their brass, and they're damn good at the primer crimping process.

11.  These things are going in for final-trimming now.  Put them in your trimmer - lube still on them - and cut them back to 1.363" OAL.  I've been cutting them shorter now so I have less to trim.  If you chop them right at the shoulder, they'll be somewhere between 1.900" and 2.000" long when you start trimming - THAT'S ALOT TO HAND-TRIM!!!  I chop under the shoulder now - still experimenting - and my initial length, to start trimming, has beenin the 1.800"-something range.  That's not bad.

12.  You may need to hit them with the VLD chamfer tool (inner and outer) while you're trimming them down.  Measure often - if you have alot to go, chamfer those fuckers.  It makes it easier to trim them down.

13.  Once at final trim-to size, chamfer those bastards again, inner and outer, with the VLD chamfer tool.  This must be done in order to make it easier to get a good, light crimp on them later. 

14.  Once they're all trimmed to 1.363", they go into a small tupperware of hot soapy water.  Run them all around in there, make sure you wash them good.  They've got lube on them, brass shavings, gunk.  The hot soapy water makes that stuff go away fast. 

15.  Toss in a squirt of Real Lemon, right into the soapy water, for the last 10 minutes.  Makes 'em pretty.

16.  Out of the water, into a small collander - hot water bath, right under the faucet, to clear all that soap and lemon juice out.

17.  Onto the paper towels, out into the AZ sun, to dry out.  Takes less than 10 minutes here, in the middle of the day, in the summer...

18.  Into the tumbler again.  Polish 'em up.

19.  Clear them out from the tumbler, take them back inside ('cause it's summer in AZ...).

20.  Prime those bastards up.  I'm running CCI 400 small rifle primers in mine.

21.  Measure/drop powder.  I'm running 150 grain Hornady FMJ BT projectiles, so I'm running 16.1 grains of H110 powder under them.  It's very, very damn close to a compressed load in this small case.

22.  Seat your bullets. 

23. Toss on a light taper-crimp, if your dies don't already do this for you.  I've been using the RCBS AR-Series 300BLK Small Base Die Set.  The seater die has a crimp function built right into it - all in the same motion.  Once you hit that final depth on the seating, it crimps it, too.  No separate action the their AR-Series Dies. All in one.  Saved one step that way...  <lmao>

There you go.  That's the process I take to turn Lake City 5.56 NATO brass into 300BLK ammo.  Might seem excessive, but those steps are there for a reason.

I sure as hell hope I didn't leave a step out - I don't think I did...  <laughs>

Fire off any questions, guys.  If a step I'm doing doesn't make sense, hit me up on it.  I'll either explain why I do it, or change what I'm doing...  <thumbsup>

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This is the mini chop saw that I use to cut down .223/5.56 brass; picked it up for about $25 at Harbor Freight:


This is my preferred VLD chamfer tool - Lyman Case Prep Multi Tool, available all over the place...


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  • shepp pinned this topic
  • 1 month later...

Messed around learning on some S and B brass that was expendable. Now I am doing my Lake City brass and those instructions above are right on the money. Turning out nicely beveled at precisely 1.368".

Edited by Sisco
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For whatever reason the chop saw I got did not have the power to cleanly cut the cases. It messed a bunch of them up. Went to Harbor Freight today, but their current mini chop saw is the same as the one I picked up from Amazon only with a different label. For $10 more I decided to try a 6 inch cut off saw. As brass is non sparking, sparks should not be an issue but I will start outside just to be safe. This is what I got.  Will let everyone know how it works.



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I wonder if you could get a carbid  tooth blade for either of those we switched from the chop sw to that at work for threaded rod strut and copper (which is similar to brass) I bought a makita metal skills saw with a  carbid blade last year it's a metal cutting MF

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  I use my Dremel tool with a cut off disk , it makes short work out of the brass . I have a couple of hundred factory 300 BLK brass now ,(along with my cut LC brass ), thanks to the Range brass picker upper . I will not be cutting any more , besides , I need all the LC for my 25-45 Sharps , which don't need to be cut at all .:thumbup:

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