Talk me out of buying a small base sizing die

[SWThomas]

So I'm getting my feet wet loading 308 for my AR-10. I posted a thread a week or so ago and a member mentioned using a small based sizing die. I'm currently using Dillon dies and have loaded 50 rounds with them. All rounds fired perfectly in my AR-10. But the comment about the die got me worried that I may be doing something wrong. What would be the benefit of switching to a small based sizing die, and what problems could arise if I don't?

Do any of you guys use regular dies to size 308 for an AR-10, and if so, have you experienced any problems?

[MontePR]

I was under the impression that Dillon dies were small base

[HackerF15E]

If it shoots fine out of the rifle you are loading it for, there is no point in getting a new die (even though they're not that expensive anyway).

Small Based dies are to increase the reliability out of autoloaders. If it weren't working with your current dies, you'd know it by now.

[NWcityguy2]

Small base dies will resize the brass to exact SAAMI dimensions. Normal full length resizing dies will get you close to that but not quiet. A small base die can give you increased reliability with a tight chamber but you will need to trim the brass more and it might cause head separation faster. If you aren't having any reliability problems then all you are doing is creating more work and wearing you brass out faster. If you throw your brass away after 4-5 uses then you are just creating more work.

I couldn't say if all Dillon FLR dies are small base dies or not.

Edit: The people to ask about small base dies are M-14/M1A reloaders. They are very popular with them.

[bigedp51]

I have small base dies for all my autoloaders, I use them when I buy once fired Lake City brass to resize them back to minimum dimensions. Remember brass tries to spring back to its fired size and a standard full length resizing die might not size the brass small enough that was fired in a machine gun chamber. Also remember to pause when the press cams over for a three count when using the small base die, this will minimize brass spring back in diameter and cartridge headspace.

After I use the small base die on once fired brass I use a standard die there after. As you can see below the military 7.62 chamber is .0025 larger in diameter so a standard full length die is already a small base die.

http://i122.photobucket.com/albums/o254/bigedp51/183911_zps5aff5dc9.jpg

Right now I'm using a small base die on "some" once fired .223/5.56 cases, some being a five gallon bucket full of brass. I'm giving my arm a break posting this, then its back to the press and my small base die. I have a bolt action .223 and two AR15 rifles that need feeding.

I'm not going to talk you out of a small base die, your going to need to buy them all. ;)

http://i122.photobucket.com/albums/o254/bigedp51/223dies002_zps4596712d.jpg

[NWPilgrim]

If it shoots fine out of the rifle you are loading it for, there is no point in getting a new die (even though they're not that expensive anyway).

Small Based dies are to increase the reliability out of autoloaders. If it weren't working with your current dies, you'd know it by now.

Exactly! If regualr Fl dies are working for you then don't bother getting SB dies. Those will be a bit harder on the brass (work it more).

I shoot .308 out of a PTR91, .30-06 out of 3 Garands, and .223 out of 4 AR15s and do not own a single small base die. If you had chambering issues then sure go for the SB die, that's what it is made for. But having success with regular FL dies means you already have what you need. Read the Sierra bullets article on case sizing for autoloaders: http://www.exteriorballistics.com/reloadbasics/resize.cfm (http://www.exteriorballistics.com/reloadbasics/resize.cfm)


In most instances, full length sizing will reduce the case dimensions enough to allow it to be used interchangeably in several different rifles chambered for the same cartridge. Contrary to popular opinion, full length resizing is commonly used by the vast majority of competitive shooters, especially in those disciplines where rapid-fire is involved. It should be clearly understood that full length sizing does not reduce a fired case to its original, unfired dimensions. The goal here is to bring the case dimensions down far enough to allow the reloaded case to be chambered without difficulty.

And about small base sizing dies specifically (my emphasis):

As we have noted, most conventional full length sizing dies reduce a case’s fired dimensions enough to allow the case to be easily rechambered, without bringing it down to its original, unfired dimensions. In some instances, this will not quite be sufficient to assure positive operation and functioning. This most often occurs in firearms that lack the camming power of a bolt action, such as semi-autos, pumps, and lever actions. Sierra has worked with a large number of these types of firearms that functioned perfectly well with conventional full length dies, and suggest resorting to small base dies only if they prove to be necessary. They do work the brass more, and will usually result in reduced case life.

[Djstorm100]

please excuse my lack of knowledge but what exactly is small base sizing design to do other than be more reliable. I guess what I'm asking is now do I know i have a small base sizing die and how does it differ from full sizing die?

[wahoo95]

please excuse my lack of knowledge but what exactly is small base sizing design to do other than be more reliable. I guess what I'm asking is now do I know i have a small base sizing die and how does it differ from full sizing die?

RCBS makes a small base sizing die which is designed to slightly undersize the case upon sizing. The benefit is increased reliability in semi autos and sometimes it elimnates the need for further trimming. I've never felt a need since a properly set up standard die works just fine.

[markm]

I was under the impression that Dillon dies were small base

Someone is paying attention!

[MontePR]

Yeah I believe it was discussed in one of your threads.

[markm]

Yeah I believe it was discussed in one of your threads.

It came up. I'm guessing the .308 is the same... but Someone posted the specs on the .223 die, and it was indeed small base. I never really gave it thought since I'd been using the die since day one.

[okie john]

please excuse my lack of knowledge but what exactly is small base sizing design to do other than be more reliable. I guess what I'm asking is now do I know i have a small base sizing die and how does it differ from full sizing die?

A small-base die sizes the lower portion of the case (just forward of the pressure ring) slightly more than a normal sizing die. They're advised when reloading for rifles that are chambered for high-pressure rimless cartridges AND that lack the camming power of a Mauser-type bolt. Examples include the Browning BLR, the various Remington pump and semi-auto models, the Savage 99, the Winchester 88 and 100, etc. The reason they exist is that some people insist on trying to match bolt-action ballistics in other action types. These actions can flex more in firing than a bolt action, which can let cases stretch, which can lead to stuck cases. That's why most sources that recommend SB dies also recommend not shooting max loads through non-bolt-action rifles and/or reducing loads for those rifles 1-2 grains from max.

The extractor in a bolt gun based on the Mauser is huge and rugged. The bolt also has integral camming surfaces specifically to help open the action in the event of a stuck case. You can literally hammer the bolt open (or stick a piece of pipe over the bolt handle and lever the action open) to remove a stuck case if needed. Then, once you get the case out, you can resume using the rifle normally. Other designs have smaller, more delicate extractors, and nothing to pound on when a case gets stuck. It's much harder to get the action open and you're much more likely to break the extractor, so you end up taking it to a gunsmith.

All of this mattered a lot more back when ammo metallurgy was cruder than it is today, but problems still do arise so SB dies are still a good idea.

Small-base dies are normally marked "SB" somewhere, usually as part of the caliber marking, but unmarked SB dies could exist.


Okie John