14"
for 32- and 35-grain bullets at 4400 to 4600 ft/sec.
12" for 39- and
40-grain bullets.
[The 14" twist did not work with 39s and 40s at 4500
feet elevation.]
12" seems to be best overall.
[The 12" twist is hard on the current crop of lighter bullets when those are driven at maximum velocity, I would be happy to try a 13" twist if I wanted to use heavier bullets. However, since I have no interest in those, I would prefer a 15" twist. In comparison testing between Pac-Nor barrels I saw no velocity difference between the 12" and the 16" twist when launching light bullets at maximum velocity – the same loads worked about the same in both barrels.]
Berger bullets are most accurate but [are relatively] delicate, I can blow them up if I push them too hard. Have not tried 50-grain Bergers, they require 9" twist but Walt is using these in benchrest with some success in a version of the PPC case. I have not had good success with Sierras to date, I think these may have growing pains[conversely, I have had very good results, different production lots perhaps?]. Hornadys are OK but not as accurate as Bergers are. Historically Norma brass has been better dimensionally and with regard to neck and shoulder annealing but Lapua will withstand somewhat more pressure.
Norma was supposed to ship the first acceptance lot of properly headstamped brass in July but we have not received it yet. [Those are now promised near the end of September 2005.]