Quote Originally Posted by LoneWolf View Post
The same COAL restrictions apply, but the different shoulder angle of the Creedmoor make it easier to reach the lands at mag length. If both the Creedmoor and 260 are setup using the same bullet at a COAL of 2.8" the 6.5 Creedmoor will not be seated as deep as the 260. Most guys that run long heavy bullets in the 260 run it as a single shot platform. Otherwise you are not making efficient use of the offered case capacity.
It is a geometry thing, got it. If both .260 and 6.5 are at 2.8 inches then the CM cartridge will be just slightly shorter in length than the .260 due to the steeper shoulder angle. And therefore the CM has an ever so slightly smaller charge capacity due to that steeper shoulder angle.

So if Mr. Briggs at NSS is offering a "match" chamber option for the .260 Rem, he is extending the leade length to allow the .260 reloader to seat these longer bullets at their optimal COAL thus negating the CM advantage, at least in a single shot application.