300 Blackout RCBS dies

Atrox88 · Jul 29, 2020

I was looking to buy some RCBS 300blk dies. Midway has two listed and I can't figure out the difference except on says "RCBS AR Series Small Base 2-Die Set with Taper Crimp" and the other says "RCBS 2-Die Set." I love that crap. I'm trying to figure out if either will work or there is a specific one I should be using.

https://www.midwayusa.com/product/1011278027?pid=614779

https://www.midwayusa.com/product/1011284542?pid=261325

Uncle Duke · Jul 29, 2020

Atrox88 said:
I was looking to buy some RCBS 300blk dies. Midway has two listed and I can't figure out the difference except on says "RCBS AR Series Small Base 2-Die Set with Taper Crimp" and the other says "RCBS 2-Die Set." I love that crap. I'm trying to figure out if either will work or there is a specific one I should be using.

https://www.midwayusa.com/product/1011278027?pid=614779

https://www.midwayusa.com/product/1011284542?pid=261325

RCBS makes and markets small base dies specifically for semi-automatic and lever action rifles. They will size cartridge cases a tad smaller in size, as well as bump a shoulder a bit more, for the purpose of ensuring ease of chambering, in firearms that don't have the powerful camming action of a bolt action rifle.

You will get a lot of mixed opinions regarding whether or not small base dies are "necessary." The tradeoff to chambering ease is that the more you work brass, the shorter its life. In practical terms IMO, the question becomes, shorter than what exactly? The answer becomes, shorter than it might otherwise be.

Speaking strictly for myself, I'm much more concerned with functionality than I am with brass life, and for that reason I use small base dies for the AR platform. That's just my preference. Could I get away with not using them? Probably. I'd be less certain if I were forming BO cases from .223 brass that wasn't originally fired in my rifle.
But for me, if I'm going to err, it'll always be on the side of doing what I can to maximize function.

j8064 · Jul 29, 2020

Thee main difference is small base dies will resize case bases to a slightly smaller diameter than regular dies to mitigate chambering issues in some AR's. I've found a couple of my rifles prefer SB rounds. In others, any full length sized case feeds and chambers fine. I have both die sets.

If you do not know what case style your 300 AAC platform likes best and if you're hung up on RCBS quality, go for the small base set. It will work your brass and shorten its life, but there are a zillion free .223/556 range cases around that can be reformed into 300 AAC.

For actual reloading (and as a better and cheaper alternative) you might consider a Lee die set. The FL sizing die and the FCD die work well vs. trying to adjust a taper crimp on other brands of dies. I've been using this set for several years and it loads very accurate ammo for me. YMMV.

https://www.midwayusa.com/product/101774921?pid=934234

Good luck.

:thumbsup:

kstone803 · Jul 29, 2020

Uncle Duke said:
RCBS makes and markets small base dies specifically for semi-automatic and lever action rifles. They will size cartridge cases a tad smaller in size, as well as bump a shoulder a bit more, for the purpose of ensuring ease of chambering, in firearms that don't have the powerful camming action of a bolt action rifle.

You will get a lot of mixed opinions regarding whether or not small base dies are "necessary." The tradeoff to chambering ease is that the more you work brass, the shorter its life. In practical terms IMO, the question becomes, shorter than what exactly? The answer becomes, shorter than it might otherwise be.

Speaking strictly for myself, I'm much more concerned with functionality than I am with brass life, and for that reason I use small base dies for the AR platform. That's just my preference. Could I get away with not using them? Probably. I'd be less certain if I were forming cases from .223 brass that wasn't originally fired in my rifle.
But for me, if I'm going to err, it'll always be on the side of doing what I can to maximize function.

This. I run the small base dies for my AR calibers. Never had an issue. And I haven't had any issues with brass life, mostly because I lose it before that becomes an issue.

Pinecone · Jul 30, 2020

I use normal dies, and the only issue I have ever had was one rifle that needed the shoulder bumped a bit more than I was doing.

IMO, Small Base dies are for IF you have a problem, then get and use them. Otherwise, normal dies are fine.

My normal die reloaded ammo gauges perfectly. So they meet SAAMI standards.

erwos · Jul 30, 2020

I use SB dies by default at this point. Had too many rounds that wouldn't chamber even after passing gauges. SB seems to fix that. I'm not going to toss my old dies out, but if I'm having chambering issues, SB sizer die is pretty high on the list of things I'm going to try.

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