I got a good deal on some RCBS small base dies and I'll be loading up some low cost plinking ammo for my M1A using inexpensive 147 FMJ BT pills and mixed LC brass.

My question is, do I need to use these SB dies, will it work the brass more than I need to? If so I'll pick up a regular .308 die.

Appreciate any and all opinions.

A small base die will size the case .002 to .003 smaller in diameter and push the shoulder back .002 to .003 more than a standard die.

I size all my once fired Lake City brass once with a small base die, and thereafter use a standard die.

Chambers and dies vary in size so nothing is written in stone.

Example, I have a standard Lee .223 die that reduces the case diameter and bumps the shoulder back further than my small base dies.

A resized case for a semi-auto should be .003 to .005 smaller in diameter than its fired diameter for reliable extraction.

Short answer is yes.

Long answer is yes, too:

http://www.zediker.com/downloads/14_loading.pdf

I would use a small base die only if I had to.Why not try a FL die before and if they still don't chamber you could use a narrower shell holder and if that will not work use a small base die.

The SB die is what you want for semi auto's and pump action rifles.
The very little bit of extra working the brass isn't going to matter much in the long run, .308 brass is very common.
For the experts by using an SB die are we shortening the life of that brass by how many loadings? Let's say you may get 15 loadings out of carefully managed brass and with an SB die you'll get 13 loadings?
If I were loading for an autoloader I waould use the SB die and forget all the hype over overworking the brass by .002"...
Good luck with your project.

I had RCBS small base and they were a pain. Sent back to RCBS and they corrected them.

IME, lifespan of LC and most NATO stamped brass is governed by sizing at the neck. Because LC is thick at the neck, the sizing die makes neck ID smaller than obtains with commercial brass.

Then when you back the case over the expander button you are working brass pretty hard the other direction. I get neck splits with LC after about 5 to 6 loadings. Frankly, that's OK with me.

Point here is the difference in case life using a SB vs a std die with mil brass will likely be zero b/c the neck sizing portions of both dies are similar.

You can open up the die at the neck sizing area so not to work the brass as much. Of course, you'll then need one sizer for LC, another for commercial.

Lots of great info here I wasn't aware of. I think I'll try the standard FL die first and see how they fit. However, the comments about the SB die are also encouraging. Thanks for the input!

Joe, Link to a relevant, recent thread: http://forums.accuratereloadin...2511043/m/7921051032

It contains a link to a pdf article by Glen Zediker. It was written as a chapter for a Sierra manual. And it's the single best thing I've read on loading for an M1A (M14)........or any semiauto in .308/7.62.

quote:

Originally posted by Samuel_Hoggson:
Joe, Link to a relevant, recent thread: http://forums.accuratereloadin...2511043/m/7921051032

It contains a link to a pdf article by Glen Zediker. It was written as a chapter for a Sierra manual. And it's the single best thing I've read on loading for an M1A (M14)........or any semiauto in .308/7.62.

Done. Thank you.

Small base dies were invented by the reloading companies to solve a nonexistent problem and to sell more dies. In 99.9 percent of the time when a guy can't chamber his reloads, it is not the base diameter, but the length from base to shoulder (might call it headspace but it isn't).
I have loaded a lot of rounds for semi autos over the last 50 years....without small base dies.
I find.

Until recently I didn't need a SB die for our .308 bolts and HKs. Then I bought a Ruger RPR. Could not get rounds assembled in WRA and LC to chamber after FL sizing with standard RCBS sizer. Brass was at, sometimes beyond, max step on the LE Wilson headspace die. A small base die solved the problem. Rounds chamber easily, and all are at/just over min step on the headspace die.

Not everyone needs a SB die. Given a mulligan, I'd buy a SB die and skip the std sizer. Amount of stretch of once fired bulk LC/mil brass will be revealed by the headspace die. Most sizes down between min and max steps with my std FL sizer. Most chambers will be OK with this. Some pieces will not make max step after the std FL sizer.

Parenthetically, on the cheap you could grind the upper surface of a spare shellholder down so to allow the brass to go farther into the FL die. I chose not to go this route.

Have yet to process a .308 case that was out of spec b/c of excess base diameter. If I encounter one it will be culled.

I buy a lot of bulk once fired Lake City 5.56 and 7.62 brass and I size it the first time with small base dies. This returns the cases to minimum SAAMI dimensions and reduces the brass springback from being fired in a larger diameter chamber.

If you read the link posted above written by Glen Zediker the case diameter should be .003 to .005 smaller than its fired diameter after sizing for reliable extraction.

I load for three 5.56 AR15 rifles and a bolt action Savage .223 and I can tell you reloading dies vary in size. And if you buy once fired brass or use range pick up brass a small base die can be needed.

While I had a Win 100 1962 vintage I used the same RCBS dies that I use for a M700 with no hang-ups. the fellow that I gave it to has had no problems either using his standard 308 dies.