The Quarter Norton Development

[miningshawn]

Your cat is essentially splitting hairs with the 25x47L. Nothing wrong with that, as I did a very similar project and ended up within 0.004” in all dimensions to a .257 Rob AI, except for freebore and neck length. Those 2 areas making a drastic difference in performance (3100+ fps w/ Berger 135 LRHT).

I mainly shoot the 25x47L now. H4350 or 6.5 Staball will likely be the sweet spot for powder. You will probably start to crunch kernels with H4350 before 41gr. I was using IMR 4451 which is a little bulkier, and had less energy density but was very happy with ~2840fps from my 1-7.5t 27” barrel. 32” should be roughly 75-100fps higher, all else equal.

Thanks for the input, I appreciate it! Three of the main reasons I didn't opt for the 25x47:

I wanted a longer neck. I feed through the magazine and wanted less bullet deflection. A longer neck also promotes less throat erosion when coupled with 40 degree improved shoulders.

I don't want any bearing surface in the powder column, only the boattail. Unless I push the touch point to 2.925" with the 25x47 and the 135 Berger or the 131 Blackjack I couldn't keep the bullet bearing surface out of the powder column. This places it outside the length of the magazine. It is also easy to source SRP brass, which is also on the radar for load development.

This project is about fixing all of the problems, I don't want to settle for anything less. I also agree that H4350 works well so far. 6.5 StaBall is coming in the next test series. I don't know if enough 4831 is going to fit in the case to get the velocities I want. We'll have to see.

I wanted to stay with a .308 parent case. I know it is splitting hairs. There is a boat load of information for the .308, not so much for the 6.5x47. I have more .308 brass than I will ever be able to use.

I never did mention... I don't expect to set the shooting world on fire, or make any money, or gain any notoriety from this project. I had the opportunity and the means and wanted to do it.