Since this has become a bit of a reference thread, adding some load data from some limited testing thus far for the 260 and 308 in case it helps someone down the road and answering a couple of questions.
Answering a question on the 260,
Weight 6 pounds, 14 ounces.
Muzzle diameter - 0.600" at the muzzle, on a 22" barrel.
Mine is 1:9" twist.
So far, in tinkering with Barnes bullets with the 260, the best loads have been:
100 gr. Barnes TTSX
44.7 H414 - avg 3065 @ 65F, again from a 22". The H414 would push it over 3100, but this was the best accuracy. Lapua brass with F210M's.
H414 is the same as Win 760, and very similar to 4350, except it is a spherical powder, and easier to find. Also tried IMR 4831 and Varget for comparison. Did not have any I or H 4350 handy to try when testing.
120 Barnes TTSX
41.8 H4350 avg right at 2800 at 65F.
Lapua brass and F210M.
With the long mag box, reaching the lands is easy and still with mag box room left over. Both Barnes loads are 0.010" off of the lands, i.e. 0.010" of jump.
For the 308, this load works in every 308 I've ever tried it.
175 SMK 43.5 Varget F210M 2.810" COAL Black Hills fired brass (same as Win).
Runout on all loads for testing is equal to or less than 0.003" and usually 0.001" or less. The insides of the necks are polished with a copper brush chucked in a drill.
