Got back to the range today with, among others, John's .338 MAI. This time with a pressure gauge attached and the 'scope securely fastened. What a difference tight screws make.

Attached are the pictures - I've even condensed them more. Be sure to look at the whole picture. Below are the 'numbers'.

.338 MAI

200 grain Combined Technology Ballistic Silvertip

54.0 grains of Vihtavouri N-150 - CCI 250 primer

Average muzzle velocity -

2795 fps

N=6
Standar Deviation - 13.0 fps

Average Chamber Pressure in PSIA -

56,300 PSIA

Standard Deviation - 1,105

.338 MAI

200 grain Combined Technology Ballistic Silvertip

54.0 grains of Vihtavouri N-150 - CCI 250 primer

Average muzzle velocity -

2805 fps

N=3
Standard Deviation - 8.6 fps

Average Chamber Pressure in PSIA -

56,150 PSIA

Standard Deviation - 1,660

.338 MAI

200 grain Combined Technology Ballistic Silvertip

54.0 grains of Vihtavouri N-150 - CCI 250 primer

Average muzzle velocity -

2785 fps

N=3
Standard Deviation - 7.5 fps

Average Chamber Pressure in PSIA -

56,460 PSIA

Standard Deviation - 469

.338 MAI

200 grain Combined Technology Ballistic Silvertip

54.5 grains of Vihtavouri N-150 - CCI 250 primer

Average muzzle velocity -

2824 fps

N=6
Standard Deviation - 12.1 fps

Average Chamber Pressure in PSIA -

59,430 PSIA

Standard Deviation - 1,152

.338 MAI

200 grain Combined Technology Ballistic Silvertip

54.5 grains of Vihtavouri N-150 - CCI 250 primer

Average muzzle velocity -

2817 fps

N=3
Standard Deviation - 5.0 fps

Average Chamber Pressure in PSIA -

58,610 PSIA

Standard Deviation - 1,034

.338 MAI

200 grain Combined Technology Ballistic Silvertip

54.5 grains of Vihtavouri N-150 - CCI 250 primer

Average muzzle velocity -

2830 fps

N=3
Standard Deviation - 14.7 fps

Average Chamber Pressure in PSIA -

60,250 PSIA

Standard Deviation - 474

While I'm not too excited about the gauged pressures for the 54.5 grain charge, the cases were showing absolutely no pressure signs and there were no other signs of pressure whatsoever. As you can see from the targets, the 54.5 charge gave the best 3-shot groups. That being the case, I'll leave it to John to make his own choice regarding charges.

I shot the MAI, a .338 WM, two 8x57s and 56 rounds of .45-70. Then I came home and processed this data. I'm pooped. I'll post the pressure curves later.

Paul