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Talk me out of buying a small base sizing die

S

SWThomas

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Jan 23, 2013
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Fort Lee, VA
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?
 
No. You can always use a S/B die, especially in an auto. You can always add a conventional F/L die for this, but think of it as just an added bit of insurance.
 
I have been reloading for a SR-25 since 1994 and I have a new GAP 10 that has over 300 rounds of my reloads through it. Both rifles function perfectly with regular dies. The only time I've needed a small base die was with a Steyr SSG 69 in 308 winchester. It has a very tight chamber near the case head. It requires cases to be sized @ .468" above the case head. Regular dies wouldn't work, but the Redding Small base body worked perfectly for the SSG 69.

If your rifles are working fine with your Dillon dies, I wouldn't worry about it. Most of the time when I've had chambering problems, it was caused by not having the die adjusted correctly by failing to bump the shoulders back far enough.
 
Dillon dies are small base. At least their 223 dies are so I would guess that their 308 dies are as well.
 
I dont use small base dies for anything, loaded for many autos & never had a problem. Think about this, why would a manufacturer build a rifle with a tighter chamber, especially in an auto? I know Browning rifles have chambers that are tight in the headspace area, but that's just a matter of screwing the die down a touch more and bumping the shoulder back a bit, the rest of the chamber isnt going to be tighter than a bolt rifle, no need for a small base die in my reloading room.
 
The only time I've had a problem with a base being too large was in a match bolt gun chamber.
All my gas guns run fine with cases FL resized in Lee or Redding standard dies.

I have a few pieces of Lapua .260 whose bases were tight in my .260 chamber.
I bought a "ring die" from a guy on accurateshooter.com.
He machined them out of tool steel, had them heat treated, black oxided, then precision ground.
Sort of expensive (over $100) but useful... I did not find out there was a problem with the cases until I tried to shoot them and they would not chamber.

The ring die works fine on a loaded cartridge, so I was able to fix the swollen bases without pulling down the loaded cartridges. It will work on any .308 family case, and I currently shoot .308 and .260, making the price easier to stomach.

I'm pretty sure he makes more than .308 family ring dies, too.

The seller can be contacted at [email protected] if anyone is interested.

Joe
 
I got a SB 223 RCBS die for my SP-1 back in 1971 cuz some gun book said I needed it. I used it for the first 50 reloads and never used it again. Still have it by the way. You don't need one for your 308, you already know it will work with your dies that you have.
 
Thanks for the info fellas!

I have the Dillon die and I also have a Lee sizing die. Which of those two would you use?
 
If your single AR-10 rifle feeds and operates correctly with standard full-length sizing dies you do not NEED small base dies.

You probably should have a small base die to ensure your cartridges consistently feed through all your rifles -- if you have multiple 308 (or 223 and 5.56 rifles); you buy once-fired or surplus brass fired from someone else's rifles (or machineguns); or you use range pick-up brass.

Small base dies size cases to very close to virgin dimensions, farther down the case wall and towards the extractor groove than full-length dies.

If you always shoot factory ammo or hand load using virgin brass (or brass fired through that unique rifle) you'll have no problems.

If you ever have problems with extraction and ejection (like torn case rims at the extractor groove) because your cases are fat and stick in the chamber you also run the risk of a slam-fire as cartridge strip off the top of the magazine and lodge before the bolt completely locks (especially if you have an auto loader with an inertia firing pin and without a firing pin spring like Armalite's).

Chances are you may never, ever have a problem -- unless you get a new custom barrel with a tight chamber.

Dillon dies are NOT small-base. Measure a virgin case above the extractor groove and compare to cases sized through a Dillon and another brand of small-base sizer (RCBS, Redding, Forster, etc.).

Dillon or Lee, check with your calipers. Here are SAAMI virgin specs:

308%20Win%20Case%20Chamber%20Dimensions.png


These are military:

b_112135.jpg
 
Last edited:
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SWThomas said:
Thanks for the info fellas!

I have the Dillon die and I also have a Lee sizing die. Which of those two would you use?
Click to expand...

The only thing about the Lee dies are they have minimum saami specs, so they tend to leave you with a shoulder that might not be moved back enough, had to send my 06 die back to them so they could trim the bottom of the die, now it works perfectly. Shoot some rounds up and size with both, see which shells go in the easiest.
 
I needed a SB FL only once in my reloading life, I acquired 1000 pieces of Blackhills 308 brass once fired out of a AI rifle, they would not chamber in my 95 Palma chamber 308, if everything is working, and your not firing brass from somebody else's rifle you should be GTG.
 
Sounds like you're g2g since you have Dillon dies.

I recently started loading for a gas gun in .308. The LC brass I had needed a small base die to "fix" the brass. I couldn't get it to size enough in my press (650 and CoAx) but I had a SB die on hand and it solved my problem.

Since it sounds like you've saved some $$ buying other dies, you should buy yourself another rifle! :)
 
If you learn to set your dies correctly for your chamber you should never need a small based die. IMHO the small based die was designed for those who reload alot of once fired miltary brass which was fired out of machine guns. This is where it really shines. Some of the MG chambers are expansive and really stretch the brass. I just toss these ones as they are not worth the trouble. If it won't fit in my Wilson case guage after running it through a properly set FL die it gets junked. Again IMHO oversizing with a SB die work hardens the brass too much and decreases the life of your brass. If you don't care about that then fine. I certainly would never use a SB die on an expensive Lapua case and I also would never use them on anything I would consider match. With brass you want to work it as little as possible to extend life. You want to just bump the shoulder .002-.003 and size the neck.
 
Danco411 said:
If it won't fit in my Wilson case guage after running it through a properly set FL die it gets junked.
Click to expand...

If a piece of brass wont fit in a Wilson gauge because the base isnt sized enough than the base of that piece of brass is GIANT as Wilson gauges are NOT min SAAMI spec case gauges they only show head space and trim length. You could dang near get an un-sized piece of brass into a Wilson gauge because they dont hold their dimensions to SAAMI(except headspace and trim length).

Sheridan Engineering has some min saami spec gauges in every dimension and if a pieces of brass passes their gauges it will chamber in any chamber of that caliber except possibly an ultra tight match chamber of some kind.
 
I load with Dillon Dies but I set them up according to what my Hornady headspace gauge tells me.

I bump .003-.005 back from my fire formed average.

My Dillon dies do not touch the shell plate and the brass gauges in a Dillon drop in gauge and it fits the rifle chamber.
 
Yes, in many cases, a small base die might not be required or necessary. But, if absolutely reliable chambering in a semi auto is desirable, a small base die doesn't hurt a damned thing and may prevent a failure to cycle even if it's one out of a thousand? Depending on how hot you load, and your chamber specs. the amount of cycles on a case, the more likely a little insurance in the form of a small base die could be a benefit.

Full disclosure: I only own one AR and it's a safe queen, so what do I know? BB
 
I would use SB dies in a AR15 or AR10 type rifle. When I did reloaded, I got tried of removing stuck cases.
 
You will probably be fine with a regular die as long as you use new brass or brass fired from your chamber. If you start using other people's brass or especially MG brass, you want a SB die.
 
I bought a Redding SB 223 body die off of our 'used gear' site a couple of years back and loaded up a box of 50 rounds. The SB die squeezed the body in to the point where I was getting gas blow-by on all of the case bodies proper and not just a little bit, in a Bushmaster upper. That was enough and I went and bought a standard Redding 223 body die from one of the group buys here and there's never been a problem.

If you need SB dies, sure...they work, but if you don't need them, then you'll be sending some of that gas back the wrong way in certain circumstances. It wasn't terrible, but ehhh.

Chris
 
OK, i have another question regarding this,,, conditions are as follows,
Alpha Brass 6.5 creedmoor RL15, running 2760fps, smk 142
brass is once fired and full length resized using hornady match dies with bushing and an expander mandrel...
heavy bolt lift on "some" shells,,, and I've managed to stick a couple cases as well as some are hard closing..
I measure using a case comparator every one, all are -.002 from fired brass, necks are all trimmed and cleaned up etc, .020 to the lands.
I'm going to say I've tried alot, but I know the brass is soft because of heavy bolt lift, so i backed off on the powder 3 grains, sent brass back for testing etc. This is a new rifle and same chamber reamer as my last rifle.
My thought is the bases are blowing out and making bolt close hard, I watched Eric Cortina's talk with speedy gonzales and he talks about the development of redding type S dies and that they were small base and how he ended up with better accuracy that way. Got me thinking....

any thoughts???
 
Shelby stark said:
OK, i have another question regarding this,,, conditions are as follows,
Alpha Brass 6.5 creedmoor RL15, running 2760fps, smk 142
brass is once fired and full length resized using hornady match dies with bushing and an expander mandrel...
heavy bolt lift on "some" shells,,, and I've managed to stick a couple cases as well as some are hard closing..
I measure using a case comparator every one, all are -.002 from fired brass, necks are all trimmed and cleaned up etc, .020 to the lands.
I'm going to say I've tried alot, but I know the brass is soft because of heavy bolt lift, so i backed off on the powder 3 grains, sent brass back for testing etc. This is a new rifle and same chamber reamer as my last rifle.
My thought is the bases are blowing out and making bolt close hard, I watched Eric Cortina's talk with speedy gonzales and he talks about the development of redding type S dies and that they were small base and how he ended up with better accuracy that way. Got me thinking....

any thoughts???
Click to expand...

Most probably the base of the case is blown out and that is the issue. That is the problem solved with the small base die.
 
What is the difference in the diameter of the base before sizing and after sizing?
 
Doom said:
Most probably the base of the case is blown out and that is the issue. That is the problem solved with the small base die.
Click to expand...
yeah i just can't believe it with the slow load, no pressure signs etc,,,, I'm blaming alpha brass for now, i'll run some lapua through it and update it..
 
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