Small Base Resizing Dies vs. Standard

[skydiver]

Chime in with your thoughts and experiences with small base dies vs. standard full length on semi-auto rifles.

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[Darkker]

Remember that not all full length dies, actually size to the same specs.
I have built, or owned over 8 different AR rifles. Only ever used my Lee full length dies, and never had an issue.
My f/l RCBS dies didn't always size to a spec that chambered properly, maybe why they are the ones selling small base dies..... Just a thought.

 

[usagi]

i need to use a small base die for my 300 blackout when resizing 223/556, since the brass dimensions seem to be all over the place. small base die gets them all in spec.

 

[eganx]

So I prepped 1000 machine gun fired 7.62x51 cases. I sized them with a lee FL die. They wouldn't chamber reliably. I bought a lyman headspace/case length gauge. I sized them again with minimal sucess. I bought an RCBS small base die set. sized them again and never looked back. I have never again used the small base die set. I have loaded for my FAL with the Lee FL die with no trouble except when using machine gun fired brass.

The M240, like most machine guns, has a generous chamber. So the brass expands to fit the chamber when fired, taking a little more effort to get to size.

 

[alphapygmy]

For my AR's I use a standard die for plinking or target ammo. On the other hand for my shtf ammo I only use a small base die. With AR's having a DI gas system I worry less about a filthy chamber causing a stoppage with small base sized brass. I gladly give up a little accuracy and brass life for increased reliability. Several times I abused my first AR to prove to myself they could be reliable by going over 2000 rounds between cleanings and didn't have a single stoppage.

 

[filsonhand]

So I am curious how much brass life is shortened using small base dies as opposed to fl dies

 

[alphapygmy]

I'm not sure how much, but sizing the base smaller works the brass more in the general area where case head separations happen. Head separation=stoppage. Yeah, it's unlikely to happen but my life may depend on that ammo. God forbid shtf I don't have the resources to train so much as to smoothly and calmly figure out what's happening and clear it while under fire. Just being a realist on my training and skill levels, but I do my best to insure when I pull the trigger my tools go bang.

 

[usagi]

So I am curious how much brass life is shortened using small base dies as opposed to fl dies

zero?

case lengthening and stretching is what gets you. or neck splits. not working the brass at the base.

 

[bballer182]

zero?

case lengthening and stretching is what gets you. or neck splits. not working the brass at the base.

Wrong. Work hardening the base by excessively sizing then firing in a chamber that is quite a bit bigger is what gets you. I'll take a neck split (not that big a deal) shortening or lengthening over a case head separation any day. Case head separation will ruin your day, probably permanently.

 

[AMProducts]

In my experience, small base vs full length has very little impact on your brass (necks usually split well before you get base expansion) life when shot in a semi-auto. OTOH if you're shooting it through a bolt action rifle, your brass life will be noticeably shorter compared to using a neck sizing die. I did quite a bit of comparison work some years ago on my competition loads for my bolt action guns, small base sizing guarantees chambering without having to use your foot to close the bolt on a bolt action gun (happens when you neck size only and accidentally switch guns). After quite a bit of testing, I found I could get about 9 good reloads before most of my .308 cases started developing neck splits. On the lot that was small base sized it was almost indistinguishable in terms of failure rate, the actual failure rates was about 8.3 for neck sized, and about 7.6 for small base sized. I also havn't really notice appreciable increases in accuracy going with neck size vs small base, the more important factor was all the brass being of similar weight, and similar age.

As a consequence of my studies, I small base size all of my brass... both that I use for plinking, hunting, "SHTF" stockpile, and competition loads. The more important issue is since most of my guns like similar loads, I don't have to spend a lot of time picking through and making sure I grabbed the right gun, and the right ammo before going out to the range.

 

[usagi]

Wrong. Work hardening the base by excessively sizing then firing in a chamber that is quite a bit bigger is what gets you. I'll take a neck split (not that big a deal) shortening or lengthening over a case head separation any day. Case head separation will ruin your day, probably permanently.

it's not work hardening that causes case head separation. it's stretching the brass.

if it really was just work hardening, then you could correct the problem with annealing. then you'd effectively have brass that could last _forever_.

but you cannot, because it's not work hardening at fault. it's case stretching. you can only shoot and trim until you run out of brass to stretch.

improper headspace often lead to excessive stretching, there are many reasons why headspace may be excessive. usually this is due to bumping the shoulder too far back.

 

[Benihaus]

I have a BAR in 7 RemMag and I have to SB size any brass that has been shot out of a different weapon. Once I have fired it through my rifle though I can go back to FL sizing.

 

[gemihur]

Per manufacturer re: SB dies
*Small base sizer dies are usually required for reloading ammunition to be used in automatic, semi-automatic, pump, slide and some lever-action rifles.
*These dies size the case somewhat smaller in diamter and also set the shoulder back slightly more than a Full-Length sizer die to ensure poper functioning in the actions of these rifles.
***NOT RECOMMENDED FOR AMMUNITION IN BOLT-ACTION RIFLES.
so there you have it straight from the horse's mouth!

 

[cookie]

Wrong. Work hardening the base by excessively sizing then firing in a chamber that is quite a bit bigger is what gets you. I'll take a neck split (not that big a deal) shortening or lengthening over a case head separation any day. Case head separation will ruin your day, probably permanently.

You want to watch for incipient case head separation I had a case separate in an AR No biggie ou just have to learn to get the broken case out of the chamber. A fired case works well.