[Unclenick]

Mr. Guffey,

My C, D, and S keys went blank some time ago (Microsoft wireless keyboard) and the N is down to the bottom edges of the letter.

Here, because I was undoing the extra shortness of the SB die, I suggested the feeler gauge used the opposite way from your method of increasing sizing, instead setting it on top of the deck for setting up the SB die to behave like a longer standard die. Feeler gauges are very versatile in that they can do both shrinking and growing of sizing this way.

I did get one of Redding's Competition Shell Holder sets to make cases come out even longer, but found feeler gauge washers that accomplish the same thing. I also use feeler gauge washers under the head of a Sinclair priming tool to fix the ram height to get a specific primer seating depth. Works a treat.


Bill,

Basically, yes, best accuracy and shorter case life (fewer reloads per case before incipient head separation or splits). For a long time, the benchrest crowd relied on neck sizing only for better accuracy, and many still use. These days you see more BR people talking about bumping the shoulder back a thousandths or two from the tightest fit to let the taper of the shoulder self-center in the case. I think part of the reason this changed over time is the methods of measuring headspace changed. In the 1950's the .30-06 was still winning the Wimbledon Cup, but that cartridge is from a time when headspace was measured from the case head to the chamber's side wall and shoulder intercept. To get the case to headspace on that corner, they made the chamber with a very slightly shallower shoulder angle than the case (all the .30-03 descendants are like that, with .30-06 and .270 Winchester being most popular). So the case had that weaker contact with the shoulder and I think neck sizing only benefits those cases more than modern designs where the case and chamber shoulders have matching angles, which benefit more from a little setback. But this is speculation on my part, and not proved. The bottom line is that top accuracy loaders have cases that fit their chambers fairly closely and the small base die works against that.

Recently, board member Hummer70, who has been the National Palma Match (1000 yard) champion twice, sent me a chamber reamer design that is just for Federal Gold Medal .308 Winchester loaded with the 168 grain Sierra MatchKing. It is all about getting that ammunition to tighter, better aligned fit.


Higgite,

It dawns on me (sometimes dawning is a slow process for me) that since small base dies are meant to overcome the spring-back of cases fired in generous chambers, which requires squeezing them an extra two or three thousandths, that some might be made so that diametric undersizing is possible if you start with a case fired in a very tight chamber. The two SB dies I have don't go quite that small, but they aren't RCBS. So I emailed RCBS to see if theirs might be that small. I'll post what I learn.