Ian
Notorious member
The velocity difference is a perfect example of something Fiver mentioned in a PM. The 165A has more bearing surface (at first, anyway), so there's more to engrave right at the start, and it's a little heavier, and the lube is different in this instance, so the powder is working harder during the launch, bumping the pressure up sooner, and putting more energy into the bullet. 4350 is very slow for the .308, especially with cast bullets, but it's obviously working.
Putting this in perspective, Will is getting within 50 fps of the velocity achieved with maximum published jacketed bullet loads, in a barrel two inches shorter than the test barrel's. Yeah, I'm impressed. I've seen cycles of good groups around 2200 fps, 2400 fps, and never made it to the next level, but I think he's there. I consider 2400 fps and 1 MOA for ten shots pretty much a stopping point, never having done much better than that in the .308. 2500 was always a no-man's land in between nodes in my rifles, but that might be changed with the addition of a barrel tuner. Part of the reason the XCB came to be was running out of case capacity in the .308 right at that last node but wanting still to fling 175-grain bullets at 2500 fps and under 45K or so pressure (my concept, anyway, had to have a 57mm case to do it). The .308 doing the same is pedal on the floor with its back against the wall, which is hard on brass, hard on throats, and hard on the shooter, and not usually a good recipe for good groups.
Putting this in perspective, Will is getting within 50 fps of the velocity achieved with maximum published jacketed bullet loads, in a barrel two inches shorter than the test barrel's. Yeah, I'm impressed. I've seen cycles of good groups around 2200 fps, 2400 fps, and never made it to the next level, but I think he's there. I consider 2400 fps and 1 MOA for ten shots pretty much a stopping point, never having done much better than that in the .308. 2500 was always a no-man's land in between nodes in my rifles, but that might be changed with the addition of a barrel tuner. Part of the reason the XCB came to be was running out of case capacity in the .308 right at that last node but wanting still to fling 175-grain bullets at 2500 fps and under 45K or so pressure (my concept, anyway, had to have a 57mm case to do it). The .308 doing the same is pedal on the floor with its back against the wall, which is hard on brass, hard on throats, and hard on the shooter, and not usually a good recipe for good groups.