small base dies

[Newtire]

I have a couple of questions on small base dies.
My son's .243 (a Parker Hale) has a very tight chamber. After blackening a number of cases and even trimming down the neck until it was about gone, it was showing rub marks on the head area of the case.

Factory new cases do not have this problem with the chambering. I borrowed a factory shell and tried it and it works great.

We bought a new set of dies and got the same thing. RCBS dies-new.

I am thinking about using a small-base die set but read somewhere that these are not for use in bolt action rifles. I am wondering how this can be? I am starting to use this little rifle and am liking it so wondered if anyone had any ideas?

[felix]

Newtire, consider yourself lucky that you have a tight chamber. After you shoot the gun with the fat-in-the-rear cases, they should settle down to proper size. Always check neck diameter and case length after every shot until there are no more changes with the load you are using. ... felix

[Newtire]

I'll give em a try and see the difference but my concern was that it wasn't a safe practice. When I say tight chamber, I mean like a chamber that was reamed with a worn out reamer. The bolt closes down hard. After I fire them though, they do work smoother. So maybe the chamber is sizing the head down then...? Guess it's gotta be?

[Patrick L]

While small base dies are GENERALLY not needed, so therefore not recommended, for bolt actions, it sounds like you have a real minimum spec chamber. I think small base dies will be the fix for that. Using small base dies, even when they aren't needed, isn't really a safety concern, it just sizes the brass down more than necessary, and that causes it to expand up more than necessary. Case life will be shortened, but I don't think its really dangerous.

You already did what I would have recommended, which is to just try a different set of dies. I once had a Lee .30-06 die set that had a sizing die that was on the big side, but still within tolerances. I loaded thousands of rounds for a few different rifles with no trouble. Then I got one rifle with a slightly tighter chamber, and my reloads wouldn't chamber. Rounds loaded on my Hornady dies (not small base) were fine. I eventually got another Lee sizer die, and that one was fine too.

So you could just keep trying dies till you get one that works, or just go with the small base dies.

[1hole]

"Normal" FL sizing dies are actually cut a little large to accomidate common generous factory chambers. They usually size heavy case webs to maybe .003-4" over SAAMI specs to help us reduce early case failure due to over working the metal.

"Small Base" dies simply size cases to the original factory case dimensions, so using reloads from a SB die is no more dangerous than firing factory ammo. In fact, for any user, if your cases are difficult to chamber use a SB and keep working!

The difference being so small may cause some to wonder about the tiny difference. But it's a metal-into-metal parts fit we are talking about and a few thousants too large can make a LOT of difference!

[Newtire]

As usual, thanks for all the advice you guys. I will let you know what happens. Thanks again!
Newtire

[Newtire]

Well, here's what happened. Pulled all bullets from cases that chambered hard and ran them thru the small base die. Now they just chamber beautifully. I fired these again last weekeknd and they now chamber great so just think I need the Small base for the first go around when using cases fired in someone elses gun. I used the regular dies after firing these loads and they still chamber great now. Got a feeling there's another .243 rifle coming in the future to a store near me.

[BruceB]

At one point in time, RCBS made ULTRA-small base dies, as well as 'regular' small-base dies, and these were specifically intended for Savage rifles.

The first decent sporter I had was a Savage 110LH in .243, given to me by my bride back in the '60s, and it definitely had a tight base dimension in the chamber. Dunno when (or if) RCBS discontinued the "USB" dies, but I'm sure there wasn't much in the way of high demand for 'em.