Q: I’m thinking about making up a 6.5mm cartridge by having my old post-64 Model 70 in 7x57mm rebarrelled.
It has never been very accurate and I’m leaning toward a 6.5 based on the .30-06 case with one good load using the Sierra 140gn SBT.
Which cartridge would be best out of the 6.5-06, 6.5-06 Improved and 6.5 Gibbs? Would there be enough of a gain in velocity to choose one of the improved cartridges?
I have a lot of AR2213sc powder. Would it work all right?
A: When you burn more powder you get more velocity, but only if you burn the right powder and AR2213sc would be as good as any other in any one of the 6.5s based on the .30-06 case.
My computer program says that when the 140gn Sierra is loaded as close as possible to 50,000psi, that 55gn of AR2213sc in the standard 6.5-06 achieves 3015fps; 58gn in the 6.5-06 Improved boosts velocity to 3130fps; and 59.5gn in the Gibbs gets 3150fps.
To me, this indicates that the Gibbs is a waste of time and poses too much work in forming cases.
My personal choice would be the standard 6.5-06 unless you think it is worth going to the trouble of fire-forming cases to gain a mere 100fps.