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Old May 22, 2002, 06:46 AM   #1
jw29650
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small base dies

I am new to reloading rifle ammunition for semi-automatice rifles and heard that the brass should be sized with a small base die. What is the difference between a full length sizing die and a small base die? I will be loading .223 for an AR15.
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Old May 22, 2002, 07:30 AM   #2
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Match Chamber?

Small Base Dies are required only for semi-autos with "tight" chambers. This includes Browning BARs, and some match chambered rifles.

The dies resize the bases of the cases somewhat smaller than do normal FL dies to allow the round to fully chamber, and to allow the rifle to go into battery.


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Old May 22, 2002, 09:38 AM   #3
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Don't do it!

So far, the only folks that I've know that needed to go to the small base die had exceptionally tight chambers, which are improper for use in an AR. The ones who have gone to them after having unreliable ammo were usually guys with RCBS standard dies. I put two and two together and saw that using standard RCBS dies commonly caused problems, so the knee jerk reaction was to use RCBS SB dies. SB dies work the brass too much.

Instead, try using a different brand of die altogether. Try Redding or Hornady FL but not SB dies.

The one I use is the Redding "s" type bushing die with a properly fitted bushing. But that's me.
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Old May 22, 2002, 10:18 AM   #4
Mike Irwin
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Small-base dies are also useful with some lever-action rifles.

You'll know if you need to switch to small-base dies, though, due to chambering problems with your reloads.
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Old May 25, 2002, 06:31 PM   #5
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Quote:
So far, the only folks that I've know that needed to go to the small base die had exceptionally tight chambers, which are improper for use in an AR.
That's not so. I had to go to small base dies in my AR-15 Colt Match H-bar. Any std. dies just wouldn't feed. The case would stick and I had to litterally hammer with a rubber mallet on the charging handle to extract the unfired round. I switched to small base dies and the problem is gone. I don't think it's working the brass that much more either. The cases measure .004 -.006 smaller the std.
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Old May 25, 2002, 09:00 PM   #6
dick w. holliday
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i've had AR's made by Colt, Bushmaster and Rock River for a total of 15 AR's at one time or another and still don't own a small base die......Dick
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Old May 25, 2002, 10:02 PM   #7
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Bowhnter, what brand die did you start with that didn't allow your cases to chamber well?
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Old May 26, 2002, 07:17 AM   #8
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The first ones were Lee's then I bought a 'cheap' set of RCBS, then a std set of RCBS.
None would work. They would all chamber in my T/C Contender, but not in the AR. I asked a guy at work to check at his club for which dies to use. They have a 3 gun league and most of the guys shoot AR's of some fasion... Colt, Bushies. Anyway the overwhelming majority use SB dies so that's what I got. You got me thinking hold on..........I have a sized and a fired peice of brass. Both headstamped WCC 99.
Here's the measurements.
neck - S -.244 f - .252
shoulder - .354 f - .357
middle - .364 f - .367
base - .375 f - .377

This is why I need SB dies in my AR. If I had some cerrosafe I could do more measurements, but .........
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Old May 26, 2002, 08:32 AM   #9
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I don't think you need that SB die. Note my second sentance. Guys having problems with standard dies andgoing to SB have invariably been using RCBS to begin with.

I dn't have any sized after being fired brass right now, but I'll make an effort to do one or two tonight for this thread.

Here's my fired brass measurements. This ammo was fired in a true match AR with a Wylde chamber. A chamber developed to provide the most reliability with slightly less space than a mil-spec.

neck at mouth: .250"
shoulder: .357"
middle: .368"
just above web: .375"

I'll get the other measurements tonight.
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Last edited by Steve Smith; May 26, 2002 at 04:47 PM.
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Old May 26, 2002, 08:39 AM   #10
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Dont go with a SB die, unless the standard wont work. I dont know of anyone, personally, that uses one. (Out of the 60 people that I shoot HP with, every week)
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Old May 26, 2002, 02:54 PM   #11
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I use small base RCBS dies for my SuperMatch and NationalMatch. My attitude is simply put:

"I would rather over work the brass and toss it after a few reloads then blow up my expensive guns because I fired one out of battery"

Look at the economics, a supermatch is what about $2500 or so, and 1000 rnds of Winchester brass is about $200. If I only use it once, that is 12,500 shots for the price of one supermatch if I blow it up. If I just re-use the brass once that is 25,000 rnds, or if I get 4 shots out of a case before I dump it (my usual) that is 50,000 shots.

After 50,000 shots, I will probably want another supermatch if I am still alive (I only put about 1000 rnds per gun per year down mine, so that is about 50 years, making me "older then dirt").

Just my thoughts.
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Old May 26, 2002, 04:35 PM   #12
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Peter, if that's what it takes for you, then go ahead and do it. However, a rifle shouldn't be firing out of battery period, so that shouldn't be a part of the equation. Good primers and a clean chamber should be all that's necessary. I shoot a HP match almost every weekend. No one that I talk to, either on the line or on the internet uses SB dies when they shoot competitively. 3000-4000 rounds per rifle per year is more on average for us. I don't htink you should worry about this, but again, if that's what you need, then by all means.

Shooting is so mental, and so very little physical, that I won't argue with you on what you decide you need.

My measurements:

neck at mouth: fired: .250" sized: .246"
shoulder: fired: .357" sized: .354"
middle: fired: .368" sized: .365"
just above web: fired: .375" sized: .374"
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Old May 26, 2002, 04:55 PM   #13
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This is interesting, as there's not much difference between the size of mine and Bowhnter's cases except that mine are set to my rifle's headspace (bump back .003") and the bushing in mine is sized to bring down the neck just enough for good funtioning and enough tension. My necks are not over-sized, so the brass will live longer.
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Old May 26, 2002, 05:35 PM   #14
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The case for the dies has a S B on it. The sizing die has SB FL on it. I find it very interesting that my SB dies are almost the same as all of your measurements. Is this just some catch 22 that RCBS has?
Maybe I should have spent the extra $$ on Reddings.
Strange, very strange.
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Old May 26, 2002, 06:27 PM   #15
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What you find strange is different than what I find strange.

You see is that the "standard" RCBS dies were larger than than of my standard Reddings. I have been seeing that for a long time regarding RCBS vice most other brands in regards to .223 rem. Many guys have been exactly where you are now. It appears that the "standard" RCBS .223 die was built with the boltgunner in mind.

What I see is that the SB is not all that different from what other manufacturers call "standard" so I retract my previous statement. However, I wil say this, the bushing I use for the neck sizing is on the large size for what many believe to be the "right" one for .223. I was instructed by my Highpower "mentor" to use a bushing that would only size the neck enough to barely touch the expander ball on the way out (not expanding anything, just graze it.) This would "sweep" the inside of the neck, but the brass would not move very much between firing, being sized, and then being expanded. I have removed the expanding potrion of that equation, and also found just enough case tension to keep the bullets where they belong...no more. In addition, the "floating" bushing allows the necks to be sized more squarely than if they were fixed to the die. These advantages are debateable, but all I nknow is that my ammo will hold 5/8ths MOA all day and that is more than good enough for HP.

One thing that might matter: I know of a few guys using regular 'ol dies, who have had runout problems, but when they switched to the Redding "s" type, they runout went away. If you're not shooting over 300 yards, it probably doens't matter, though.
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Old May 27, 2002, 08:36 AM   #16
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Steve,

I agree about the mental comments.

I do not have the time to compete anymore, so my rifles are "legacy" to an earlier time. For my guns, the normal RCBS dies would size the cases so that 1 time in 100 or so, the bolt would close "almost", but not quite locked. It never caused a problem, but I got really chewed out at a match for shooting it that way by some Military instructor and he scared the tar out of me. He convinced me I was playing with fire and eventually one un-latched round would blow my guns up. We are going to ignore the built in safety of the M-14's because these are Springfield M1A's and after pulling my trigger group he said my receivers were "on the ragged edge" but safe.

With that said, I switched to SB dies and I have never had a round that would not completely chamber and lock.

So, I now shoot the m1a's for fun and for memories and use the SB to make sure I have a fully loaded and locked round. For a long time afterwords (years literally) I would eyeball the bolt to make sure it was closed and locked before pulling the trigger. Mind you, I never had a problem, it was all in my head.


I would guess your summary is correct. RCBS makes in my terms a "Loose" die for the bolt gunners and the SB is more like the Redding's and would be called "small base or tight" by RCBS standards.

Thanks for the dialog, it brought back some good and not so good memories.
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