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First Range Report on John's .338 MAI
Old 03-30-2005, 02:11 PM
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Default First Range Report on John's .338 MAI

When I visited John here while back, I brought home with me his .338 Mauser Ackley Improved to work up loads for it. I haven't yet, but will be soon attaching the pressure measuring hardware. This preliminary report is just load/velocity/precision data.

John's goal was to produce a cartridge in .338 caliber that would get close to .338 Win Mag external ballistic performance while still fitting in a "standard" length action, specifically, a milsurp Mauser. He had the reamer done by Dave Manson so that the chamber would be optimally sized for the Combined Technology Silver Tip (CTST) at 200 grains. His Load From A Disk software suggested that a charge of 55.1 grains of Vihtavouri N-140 would yield a muzzle velocity of 2504 f/s with a chamber pressure of 53,333 PSIA. This charge represents a load density of approximately 90% and a charge-to-bullet ratio of .276.

Load From A Disk did not have data for N-150, but John thought that it might be a better choice as load density could be increased. He and I both like to have load densities as close to 100% as is reasonable. I fire-formed 20 cases and calculated what an appropriate N-150 charge range would be. Based on those calculations I loaded 5 each with charges of 52, 54, and 56 grains of N-150. I happen to like the Nosler 210 Partition in my .338 WM, so I loaded 5 of those bullets in front of 52 grains of N-150.

At the range I used 3 of the 52 grain charged 200-grain CTSTs to sight the 'scope in at 25 yds. The rest of the bullets were fired for precision and velocity at 100 yds. below is the velocity data.

200 grain CTST
52 grains of N-150
2749, 2725, 2740, 2702, 2722 - Mean=2728, St. Dev.=18.06

200 grain CTST
54 grains of N-150
2821, 2816, 2821, 2828, 2820 - Mean=2821, St. Dev.=4.32

200 grain CTST
56 grains of N-150
2907, 2917, Mean=2912 no St. Dev.

210 grain Nosler Partition
52 grains of N-150
2697, 2690, 2696, 2701, 2693 - Mean=2695 St. Dev.=4.19

I was doing a bunch of other stuff at the range that day as well, and the target with the groups for the 210 is at somebody else's house for the time being so I cannot present its precison information. As I said above, 3 of the 52-grained CTST-loaded cartridges were used to sight in the 'scope. That left only 2 for use at 100 yds. The first 56-grained load showed some signs of pressure. I fired one more round, and it showed the same pressure signs, so I stopped there. (Upon later inspection, the primer pockets were a little loose. Clearly too much pressure.) Therefore, the 56 grain group is also only a 2-shot group. Personally, 2-shot groups are not particularly interesting to me, especially when I'm working up loads. I include them here only for "completeness".

Finally, for comparison, I'll post the average velocity I get with some Hornady 225s in my .338 WM.

.338 Winchester Magnum
Hornady 225 SP
69.0 grains of H414
Mean=2839 St. Dev. 12.3

So... looks like John has met his goal of approaching .338 Win Mag velocities from a 57mm Mauser case. The 200 CTST at 2821 f/s in front of 54 grains of N-150, compares very favorably with the 225 grain's 2839 f/s out of the .338 WM.


Last edited by gitano; 03-30-2005 at 03:18 PM..
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