Small base die for semi-autos?

Only time I needed it was when shooting once fired military stuff.

Your rifle will tell you if you need an SB die. I have never needed one, and that's loading for 3 different .308 rifles, including my M1a, or, for that matter, something like my M1 Garand or my AR's. Maybe I'm lucky, dunno.

I've never needed a SB die in my 40+ yrs of hand loading, including loading for BAR's which are known to be tight.

If the FL die doesn't size brass down enough then try the SB die.

You (may) need it for (potential) prior-military-use brass.
But only once -- thereafter normal sizing.
(IME)

When using LC brass for 308, I had problems with my M14 chambering brass. My 700 milspec had hard bolt closing. SB fixed that. Like it was said earlier, if you have the problem, you’ll know soon enough.

If you are reloading military once-fired brass, and want 100% reliable functioning, SB dies are essential. I use only SB dies for semi autos. You might lose one or two reloadings from each piece of brass, but that's a trade off I am willing to make. YMMV.

frogfurr said:

This is getting a little complicated. If I purchase once fired Lake City brass due to it's reputation for longer brass life I will then have to buy a small base die and shorten the brass life of the Lake City brass? Wouldn't I be better off staying away from the military brass altogether?

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The best answer is to spend your hard earned greenbacks on imi or ppu brass for a semiautomatic. A die trying to fix an out of spec case will never be better than a new one fired in your gun. You may even check starline I hear there rifle trends to the military thickness.

AJC1 said:

The best answer is to spend your hard earned greenbacks on imi or ppu brass for a semiautomatic. A die trying to fix an out of spec case will never be better than a new one fired in your gun. You may even check starline I hear there rifle trends to the military thickness.

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What makes those 2 companys better? Thickness?

Yankee1986 said:

What makes those 2 companys better? Thickness?

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Ppu and imi are well respected military brass that handle semi abuse. My plug for starline was based on JRBs testing. I'm 100 on the first two an 80 on the third.

For cases fired in your rifle, you should not need a small base sizing die.

But, if you use cases fired in another rifle, you may need a small base die sizing die. The operative word is “may”.


Once fired military cases were probably fired in a machine gun these days and suck for reloading. I had many case head separations with the first and only batch of military once fired cases when fired in my M1A. Make sure you know what kind of gun once fired cases were fired in before buying.

As a normal thing, I small base size all cases used in my semi-auto rifles if a small base sizing die is available. I find no loss in case life versus a standard die and it is cheap insurance against chambering problems.

For instance, cases fired in my Colt Match Target then sized with a standard sizing die will not chamber in my Compass Lake Service Rifle AR-15. It is a bitch to get a jam in the middle of a match

If I small base size the cases they chamber just fine.

Finally, most case gauges such as Dillon or L. E. Wilson measure shoulder position and overall case length. They are cut generously in the body dimmension.

The Sheridan case gauges are cut to SAAMI dimensions and will gauge the body dimmensions.

Read the fine print from the manufacturer.

My experience, opinion, and operating procedures. Hope this helps.

dh1633pm said:

When using LC brass for 308, I had problems with my M14 chambering brass. My 700 milspec had hard bolt closing. SB fixed that. Like it was said earlier, if you have the problem, you’ll know soon enough.

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True. You will know soon enough. After I bought my Remington .308 AR10 clone, I even had problems loading factory Federal Power Shok (blue box). Remington was fine, but the Federal ammo would not chamber. So then spooked ... I bought a small-base set and have zero problems with my rifle and reloads...but for me, no more Federal Factory buying.

Keep in mind that though small-base dies size smaller, it is still not sized as small as Factory Remington. Don't know about Winchester factory in that caliber. I also haven't noticed problems with LC brass sized the same way, but with M.G. LC, I had to size then turn 90 degrees and size again. (old hard and over expanded brass) With such, it is probably best to anneal if you plan on longevity.

I will say that that Remington AR-10 clone is way more accurate than I expected.....maybe due to the tightish chambering? I small-base size all my semi-auto rifle now.....escpecially since Dillon admitted a few years ago, that ALL their rifle dies size to small-base dimensions. Good enough for Dillon....good enough for me...........it's called insurance IMO. I may not need such for some rifles, but I like the idea of ammo that will function in any within-spec rifle.

Once a brass case enters and exits the chamber ok, making it smaller only creates a situation where it can be worked more.

For me “under” dies are not something I would consider.

If I had one rifle that would not run on factory ammunition, I would fix it. Who knows I might want to run factory ammunition sometime.

If I had a size die that could not return a case to factory dimensions, I would replace it.

At least that’s how I have avoided needing a special die for standard calibers.

Someone tell me how much a small base die reduces the body diameter at the .200 line compared to a standard full length sizing die.

In thousandths …

South Prairie Jim said:

Someone tell me how much a small base die reduces the body diameter at the .200 line compared to a standard full length sizing die.

In thousandths …

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I don't believe there is an industry standard. The only die I've seen with published numbers are forester in the match 308 line of products.

AJC1 said:

I don't believe there is an industry standard. The only die I've seen with published numbers are forester in the match 308 line of products.

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Exactly !
Dies are cut from re sizing reamers that are spec ed based off of chamber reamers and they may vary .002 -.004
Who makes a specific small base die and what dimensions is the die capable of producing ?

frogfurr said:

I recently purchased a M1A and will start reloading soon for it. I purchased a new die set with a FL sizing die. Will I need to buy a small base die also?

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It depends on how much sizing your die is producing, you need to measure the brass to know for sure.

for a straight-wall case, get second sizing die and cut it down until it sizes the case all the way down past the base. as others have said, do this only if the normally resized case doesn't fit in the chamber.

brian pearce had this problem with 357 magnum sized cases fired in a levergun, not fitting in his revolver because of the bulge in the base of the cases. he wrote an article about it in handloader magazine a while ago. [might have been a 45 colt chambered levergun and handgun, i don't remember, but the concept is the same].

luck,

murf

I only reload for a Criterion barreled Garand. I have used mostly military brass, foreign and domestic, and never needed a small base die. Perhaps because I didn't know I needed one (?), I started with my Lee dies. Every round chambered quite well...

jmorris said:

Once a brass case enters and exits the chamber ok, making it smaller only creates a situation where it can be worked more.

For me “under” dies are not something I would consider.
If I had one rifle that would not run on factory ammunition, I would fix it. Who knows I might want to run factory ammunition sometime.
If I had a size die that could not return a case to factory dimensions, I would replace it.

At least that’s how I have avoided needing a special die for standard calibers.

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To each their own.....I just went downstairs and checked on Winchester brand, and it feeds and chambers that just fine. I don't buy the exoteric brands, so I can't say with those. So actually it was just the Federal blue box I owned. But the possibility of reloading LC brass (which I have a lot of) to something approaching that Federal box, is possible maybe even probable. So you're saying rechambering the gun is preferable to just squeezing reloaded bases 2 thousands Dia. (I measured it) with a S.B. sizer?

Two reasons why not IMO.....1: Most of us aren't machinists, or gunsmiths....costs of hiring it done would be way more than buying 1 sizer that fixes the problem. 2: Would prefer the accuracy of the tighter chamber, when it loads everything else but Federal blue box. (And maybe that's just a Q.C. problem with those Federals).

If my rifle baulked at loading Winchester or Remington I'd have taken the rifle back, or if I couldn't.....find a gunsmith....but it didn't and s.b. bases make my reloads super dependable.

You said, "If I had a size die that could not return a case to factory dimensions, I would replace it."

That'd be every normal sizer made including Dillon's normal (S.B). Even S.B. dies don't squeeze bases all the way to normal factory dimensions. Just a little more than regular dies. 1 thousandth less radius.

I would not think your M1-A would need small base dies. I would start with a standard FL die set and add a separate small base sizing die later on if needed.