IO, I shoot the 50's at 3800 in my rifle, IMI brass, CCI BR4's, N-133 in a 14 twist, 27 inch barrel. 3800 is not the max, but I don't like full length sizing brass. I can squeeze another 50 fps out of the case, but why? Hart stainless barrels are on both my 223 AI's that have zero freebore, .2245 throat, 1 1/2* leade angle, .250 non turn neck, minimum SAAMI dimensions on body.
Likewise, I shoot the 55's at 3650 with N 135, same 27" barrel.
Groups with the 50 and 55's are in the high 2's.
The 23" barrel is 100 fps slower than the 27", don't know if it's added length or just difference in barrels.
Benchmark, H335, H322 will not get the above velocities, nor will a fast twist barrel, it takes a lot of energy to twist a bullet and the result is higher pressures and a slight loss of speed. Only N133 with the 50's and N 135 with the 55's give these velocities, and accuracy is on the level of the 6PPC's that I have.
I think that Brad posted pics of the 75 and 50, it is what we call a long leade in that chamber. I'm guessing that You probably have .140 freebore in that chamber. 0.140 is equal to about 2500 rounds of shooting in leade growth, perhaps more.
These are not intended to be 1000 yard rifles to shoot steel plates with, they are live varmint rifles.
IO, you indeed have the correct set up for dinging steel at 1000 yards, and also to kill a deer/hogs with. 60g Nosler partition in an 8 twist would blow a good hole in a deer.
