I am looking at getting an RCBS X die and they have them in small base. I am shooting a 308 Marlin Bolt rifle but plan on getting a AR-10 some day will the small base serve any purpose for me or should I get the cheaper one that is not a small base?
I am always so amazed at the negative opinions I see on small base dies. And they are so strong!
YepWhat shortens case life is inducing an excessive headspace condition by bumping the case shoulder back too far, which can be done with any sizing die.
I also have reamer cut gages. I have asked the gunsmiths who chamber my match rifles to use their chambering reamers and cut me a dimensionally correct chamber from a barrel stub. I can use this gage to tell me if my ammunition is too fat as well as being too long.
I now can gage brass in a virtual chamber. This has lead me to the use of small base dies. In the attached oicture I found two huge fired WRA 68 cases. One would drop all the way in the Wilson gage, but the other would not drop in the reamer cut gage.
After sizing with a standard Lee sizing die, one case would not drop all the way in the reamer cut gage. After sizing with a Redding small base die, the other case would drop in the reamer cut gage.
1. Were the oversized fired WRA cases fired in your match chamber?
2. If not, would cases fired in your match chamber and then resized in the Lee full length die chamber in your match rifle?
I would guess the web area is not so much the problem, but more spring back of the brass shoulder after sizing. If GI chambers are longer as shown here http://www.303british.com/id36.html Then this rule would apply when using standard dies.>Machineguns tend to have very generous chambers and the web area of the case is typically blown out of spec,
I feel/guess, spring back of the shoulder is the problem, this is corrected by small base dies, much like forming dies. I have never had this problem with M16 223 brass, when using it in different rifles. When sizing 308 GI brass fired in M14s to use in 243win, the standard 243 die could not push the shoulder back far enough for the bolt action to be closed without extra pressure on the bolt handle. Belt Fed machine gun brass may produce a very different result. USSR has much more experence then i, shooting the 308. http://www.thegunzone.com/30cal.htmlForming vs. Sizing
Case forming dies are usually cut to size the case slightly smaller than the minimum SAAMI (Small Arms Ammunition Manufacturers Institute) dimensions, to account for the brass case's tendency to spring back after sizing.
Our full length sizing dies are cut to size the case closer to the middle of the SAAMI dimension, because that is where most rifle's chambers are made, and to size to the minimum would shorten case life. Whether or not our full length sizing die will work as a case forming die depends upon the chamber dimensions of your rifle, and how much spring back there will be when sizing the case.