Dies, etc, for 300 AAC Blackout on AR platform?

[leam]

I haven't done any rifle cartridge reloading yet, just straight walled pistol brass. My plan is to load 300 AAC Blackout for an AR platform using RCBS dies in my Rock Chucker. I see two different die sets: Full Length and Taper Crimp. Which one do I need? Both? Something else? Is a case trimmer recommended? I assume bullet lubing is required.

 

Thanks!

 

Leam

[HoMiE]

I’ve had better luck with the small base/taper crimp dies in ARs. Full length die may not set the shoulder back far enough if you are using brass that wasn’t fired from your rifle. Are you planning on cutting down .223/5.56 cases to reload 300bo or are you using 300 bo once fired brass? You will definitely need to cut down 5.56 brass. 

[cvincent]

It looks like the taper crimp set is a small base sizing die. The full length is not. Small base sizes full length as well, but a thousandth or 2 smaller than standard dies. Looks like the seaters are a seating/crimp combination die. I've never used a combo seating die. So can't comment. I use a Dillion
trim/size die for sizing. Lee seating and FCD for crimp.
You don't need both sets. I would probably get the Lee set. That's just me though. You will likely need a trimmer, since you're loading on a single stage, assuming not a large quantity. you could just use a Lee trimmer chucked in a drill.

Lube is required. I like the Dillon lube or homemade lanolin/alcohol lube.


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[leam]

6 hours ago, HoMiE said:

I’ve had better luck with the small base/taper crimp dies in ARs. Full length die may not set the shoulder back far enough if you are using brass that wasn’t fired from your rifle. Are you planning on cutting down .223/5.56 cases to reload 300bo or are you using 300 bo once fired brass? You will definitely need to cut down 5.56 brass. 

 

My thought was to get some once fired already shaped brass since I''m new to this. Brownells' s has some. Right now there are a lot of moving parts; brass, bullet choice, powder selection, load workup, etc. Sort of determines what my Christmas season will be. 

[leam]

6 hours ago, cvincent said:

It looks like the taper crimp set is a small base sizing die. The full length is not. Small base sizes full length as well, but a thousandth or 2 smaller than standard dies. Looks like the seaters are a seating/crimp combination die. I've never used a combo seating die. So can't comment. I use a Dillion
trim/size die for sizing. Lee seating and FCD for crimp.
You don't need both sets. I would probably get the Lee set. That's just me though. You will likely need a trimmer, since you're loading on a single stage, assuming not a large quantity. you could just use a Lee trimmer chucked in a drill.

Lube is required. I like the Dillon lube or homemade lanolin/alcohol lube.

 

Thanks! Trimmer, lube. taper crimp die. I've been with RCBS products for a while and their customer service keeps me pretty loyal. Doesn't stop me from lusting after some of those big blue things though. 

 

First load will be for 100 yard accuracy and reliably cycling the action. We'll see where it goes from there. Not doing anything super hot.

[bigedp51]

I buy bulk once fired Lake City 5.56 and 7.62 brass and use my small base dies at least once to size the cases back to minimum SAAMI dimension.

Also if you pickup any range pickup brass it good to size these cases with a small base die because they were fired in so many different chambers.

Chambers and dies vary in size, as a example I have a standard Lee 223 die that will size the cases smaller in diameter and push the shoulder back more than my RCBS small base die.

 

Bottom line I have no problem using small base dies as long as the shoulder is not pushed back excessively. A small base die will reduce case diameter and push the case shoulder back more than a standard die. I keep my shoulder bump to .003 on my AR15 rifles using Redding Competition shell holders.

 

A good gauge to have is a Hornady cartridge case headspace gauge to measure your "fired" cases and set your dies to the correct amount of shoulder bump.

 

On a semi-auto the case should be .003 to .005 smaller in diameter than its fired diameter. This smaller diameter allows the case to spring back from the chamber walls and extract reliably. And shoulder bump on a semi-auto should be .003 to .006. I only bump my shoulders .003 to help reduce the chance of case stretching and case head separations. And a over gassed AR15 can have the bolt to start moving to the rear when the case is still gripping the chamber walls.

 

The RCBS AR series small base dies I have reduce the case diameter less than .002 more than the average normal full length die. And its excessive shoulder bump that causes case head separations. 

Edited November 12, 2017 by bigedp51

[OrondoShooter]

The small base RCBS dies work the best.