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Old January 4, 2020, 03:31 PM   #1
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300 blackout die recommendation

Hey all,

I'm going to be getting into reloading 300 blackout, and I'm in the process of assembling a 300 blackout AR pistol. I'd appreciate a recommendation for reloading dies. This will be out of a 10.5" Ballistic Advantage Barrel, looking to shoot 220 grain subsonics. I don't need bench rest accuracy. I don't know if I need neck sizing, full length sizing, or both. I have an RCBS rock crusher supreme, and a Lee Loadmaster. This will be my first rifle caliber. I've used Lee dies before and that would be my default, but I'm wondering if there is a gem of a die that is a must-have or very useful, kind of like the Lee Factory Crimp die was for 9mm.

I appreciate your input.

edit: spelling, was in a rush

Last edited by dyl; January 4, 2020 at 11:09 PM.
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Old January 4, 2020, 04:02 PM   #2
T. O'Heir
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RCBS kit comes with a life time, no questions asked, warrantee. However, the brand of die makes no difference. Neither does the brand of press.
Read the rifle how-to chapter in your manual.
Any semi-auto requires FL resizing, every time. Semi's also require paying attention to the case length(SAAMI says 1.368" -0.020". That's the 1.368 minus 20 thou or 1.348" is the absolute minimum case length. Trim-to is 1.363". The whole thing is a lot less complicated than it sounds.) and OAL length(SAAMI says 2.260" is MAX OAL. Using the Max every time with any bullet weight saves a lot of mucking around.)
You will need to check case lengths every time, but you trim, chamfer and deburr, as required(if they're shorter than the Max OA case length given in your manual, they're fine.) only. BNIB brass requires all that before loading. The chamfering of the case mouth replaces the wee flare you put on pistol cases.
No neck sizing only, ever.
Crimping rifle ammo usually isn't necessary except for hot loads and ammo used in a lever action. Haven't ever crimped any ammo I've ever used in my M1 or M14. No fuss and better accuracy.
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Old January 4, 2020, 06:19 PM   #3
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If you’re not looking for benchrest accuracy, Lee dies are hard to beat. They’ve worked well for me.

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Old January 4, 2020, 06:43 PM   #4
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I have both RCBS and Hornady 300 BLK die sets. I would highly recommend them both. Both sizing dies will push shoulders of cut off .223 cases back to the required dimension and a little past. The Hornady seating die with sliding alignment sleeve has the die body a little short which only gives a few threads in the press but it seats straight bullets. Get the sets with roll crimp seaters unless you shoot all or a lot of lead bullets, then I'd get the RCBS set with a taper crimp seating die. Only one set, I'd pick RCBS.
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Old January 4, 2020, 07:00 PM   #5
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There have been lots of complaints from guys making 300blk brass and using Lee dies.

If you are looking to make your own brass out of 223 brass, id get the RCBS fl dies.

Check out as a resource. Lots of GREAT loading info on that site.
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Old January 4, 2020, 08:04 PM   #6
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I have the Lee die set and also the Lee FCD-it is the only set I have used.
I have only reloaded already formed casings which the Lee works good on.
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Old January 4, 2020, 08:44 PM   #7
Ralph Allen
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For an AR, get RCBS small base sizing die set.
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Old January 6, 2020, 05:31 PM   #8
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I've been using the Hornady set with no issue forming or resizing. bonus free bullets with purchase.
Just a dude with stuff.
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Old January 6, 2020, 08:05 PM   #9
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I can't believe I have been reloading 300 blackout for 9 year now. It does not seem like it has been that long. I use Redding Competition Dies. Yes they are way more expensive BUT I have used Lee and Hornady and in testing the Redding does provide less runout. I have documented my entire blackout journey here

11 pages long (plenty of pictures) so grab a beer or a coke I do believe it is very informative. I even explain how you can take a 221 fireball case and neck it out to 30cal to the exact dimensions of the 300 blackout. I call it my self proclaimed largest 300 blackout data site on the net. I have tested a lot of factory ammo and reloads in 7 different rifles across the chronograph and on target. I publish all of this data there. I often add to it as new manufacturers come out with new loads or I develop a new handload. it has been a blast and continues to be very fun.

Good luck if I can be of help let me know.
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