Home Forums Hunting & Shooting Express Rifles and Big Bores Only The great 458 Winchester. Everyone should own one at least once

Well, it is about time we had a Sir Darryl at the Square Table.
Do you accept the title, odonata ?

The McGowen on my M70 is 23" long and is only a few fps slower than the 25" Shilen for MV.
The McGowen slugged at a true 0.458" groove diameter, minimum for SAAMI.
The Shilen is closer to 0.459" in groove diameter, SAAMI satisfying, exceeds the minimum by less than 0.001"

What makes for a faster barrel if both have the same length, chamber, throat and twist ?
Tight and smooth rifling, I guess, and the McGowen is tighter and at least as smooth as the Shilen, I guess.
The 23" McGowen and the 25" Shilen both did +2500 fps with the 400-gr GSC HV and 80.0 grains of AA-2230.
That was in pre-Hammer days.

Anyhow, speaking of speediness, here is the 404-gr at 2600 fps JUSTIFIED for the .458 WM+:

Look at the Woodleigh manual for the .458 Lott using the 400-gr PPSN cup&core, WeldCore.
That is a short bullet, 1.152" BOL, short nose projection, crimped on the cannelure the COL in the .458 Lott is 3.465".
They use 83.0 grains of Benchmark as a maximum load giving 2500 fps MV
and 87.0 grains of H4895 (COMPRESSED) for max load giving 2570 fps MV.

The 450-gr HYDRO (BOL = 1.452") was loaded to COL of 3.6" or less and used 85.0 grains of Benchmark (COMPRESSED) as max load: 2480 fps
Same bullet with 86.0 grains of H4895 (COMPRESSED) was also a max load: 2450 fps

All of those max loads are supposed to be less than 62,500 psi.

Seems like the 404-gr Shock Hammer (BOL = 1.440") loaded to 3.580" with 84.0 grains of Benchmark
in Norma brass might be a quite reasonable load regarding pressure (in the .458 WM+)
since the bullet is shorter and lighter than the HYDRO that was loaded with 1 grain more powder, in smaller capacity brass case.
Low drag PDR bands on the Hammer might be as slick as the brass HYDRO, maybe slicker.
And there is that thing about the longer throat on the .458 Winchester Magnum too.

I do believe this is a practical load for single-loading in any .458 Winchester Magnum, Bolt Action or Ruger No. 1:

404-gr Shock Hammer
Norma Brass Case
F-215 primer
COL = 3.580"
Propellant = BENCHMARK 84.0 grains
MV = 2612 fps
One-hole 3-shot group at 50 yards.

That was in a Pac-Nor 1:10" twist of 24.25" length, SAAMI .458 Winchester Magnum chamber.
Pac-Nor slugged same as McGowen.
Twist has insignificant effects on pressure and velocity for the small difference of 10" versus 14".
Generally in the 20" to 25" range of barrel length, you only lose about 15 fps per inch of barrel shortening,
with a given barrel chambered for the Mighty .458 Winchester Magnum.
You'll lose more per inch for shortening below 20"
and gain less per inch for lengthening above 25".