Do I need a small base sizer die? Pics of fired brass...

Dultimatpredator

Dultimatpredator

Well-known member
Well, I already ordered a SB 243 rcbs die set and it arrived today so I’ll be using it. I tried some standard sizing dies and the ammo fed and functioned fine in my rifle. I tried the ammo in my Lyman checker and a couple loaded rounds did not want to easily drop out of the gauge. What was head scratching is most my fired brass fit loosely in my Lyman checker as well. I had a few fired cases that did stop just short of being flush with my checker and I had to push them out from the backside. So I would assume I have a pretty tight chamber? I did also drop my rounds in the uppers chamber to makes sure they fit before firing. Here’s a pic of the fired cases. I would assume running my brass through a small base die will eliminate some of the wear? Or I’m guessing I just have a ruff chamber that caused the expanded cases to get all scratched up when getting kicked out? I did check my OAL length and loaded the tested ammo forty five thousands short of the lands.

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The question of a SB verses regular die about never has a definitive answer, it can depend. It sounds like a semi-auto AR chamber? That’s one to be careful with so you don’t stick a round while out hunting.

I bought a Redding SB die a while back for some 223 loading, cost more but I like it.

Not sure if it matters but at times I offset the case 180 degrees & run the case again through the sizing die, properly lubed of course.
 
IF, your standard sizing die sizes enough to function in your guns, then don't worry about it. If they get sticky after several firings, then you will probably need one. Instead of only relying on over all length, keep a check on your brass length.
 
Yes, I’m working with a 243 AR10. I tried the small base die on some brass given to me. The cases sized in the small base die definitely fits looser in my Lyman checker gauge compared to the cases sized with the standard die set. The standard die sized shells do fit in my Lyman checker but there is VERY little clearance. With the standard sized die I can foresee a future issue of a of the cases sticking or jam from dirt, grime build up in the chamber, or heat expansion, making a tighter case to chamber fit. I’ll have to load a few and try them out. I do trim my brass after every firing as well.

 
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Many Firearms of the semi auto type require SB dies. Not all but many. It does tend to overwork the brass, but with a semi auto you will be loosing brass anyhow.
 
Instead of using a small base resizing die, you might consider using a Redding body die. Brownells usually has them in stock.

If you resize your brass using a standard full length resizer and cam over, that should do it. I use Redding dies and on the 30-06 FL resizing die, if I don't cam-over, there will be an occasional round that will either chamber hard or not at all - camming over, I never experience a problem.
 
I never ever "cam over"

I have in the past when my RCBS Rock Chucker was my primary loading press. Those are designed to accept some "cam over"

If you do that on other types of higher end presses you are just flexing the cast iron.....

If your reloading system is not allowing you to get sufficient sizing i would either: Get a new die, swap shell holder brands around until you find one that works and/or get new brass.

If none of that works, i would get a new barrel with proper head spacing. Because that is the problem.
 
No one ever responded on all the scratching. That chamber is definitely rough and could use a bit of polishing. You don't want it bright as a diamond in a billy goat's butt but it can certainly be improved on. A bit of roughness is needed to let the case adhere and decrease bolt thrust.

Choice of standard vs. SB will do nothing to eliminate these marks BTW. Nothing here indicates a head space issue. Even if you have a minimum chamber there is no reason you can't size for it. We make cases fit wildcat chambers all the time that are not "standard" and it is merely a matter of adjusting up and down, maybe grinding a shell holder or if you have the ability and do it yourself or want to spend the money sending it to the manufacturer to shorten the sizer body. Dealing with a factory produced chamber is easy peasy in the big scheme of things be it long or short.

Greg
 
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