Idaho Trecker
Well-Known Member
After some setbacks and troubleshooting the 338 Mega is up and running! After actually measuring the barrel it is only 21.25". My testing has shown that this round does well with a shorter barrel also. My barrel is chambered with the "long" reamer which has a longer freebore. Rich was kind enough to get me a bit of the ADG 300 WSM brass to use for initial testing until the proper length brass is done.
So far I have basically just been able to run pressure tests, with very little accuracy testing, using the 250 grain Berger, 265 grain Long Range Accubond, and the 285 grain ELD-M. Powders tested so far include RL 26, N555, RL 16, Hybrid 100V, and IMR 4451.
Disclaimer: All loads with RL 26 and 285 ELD-M and 265 LRAB used a drop tube and with bullets seated .005-.010" off lands. 250 Berger was seated .080" off. All speeds taken with Magentospeed. These were just pressure tests in my rifle an not to be taken as load data. I stopped at pressure signs that were obvious to me (extractor marks, extra bolt lift, cratering or flattening of primer).
285 ELD-M Fed 215 primer RL 26
72 grains 2635 fps
73 grains 2666 fps
74 grains 2706 fps
75 grains 2747 and 2735 fps
75 grains was max pressure and capacity. Only the faintest shadow of an extractor mark
265 LRAB Fed 215 primer RL 26
74 grains 2741 fps
75 grains 2770 fps
76 grains 2807 fps
77 grains 2845 and 2856 fps
77 grains was also max pressure and capacity. Faint shadow of extractor mark but harder bolt lift
250 Berger Fed 215 primer RL 26
79 grains 2987 fps
80 grains 3013 fps
Both these loads were hot. I will post a picture of the 80 grain load case head. 80 grains was excessive and 79 grains is where I would normally stop and go 2 grains lower to start playing.
Fed 215 primer N555
72.5 grains 2758 fps
73.5 grains 2780 fps
74.5 grains 2810 fps
I could have possibly fit 1-2 more grains in but basically out of capacity. Didn't pressure out.
Fed 215 primer RL 16
69.5 grains 2791 fps
70.5 grains 2811 fps I made a jump to find pressure next.
73.5 grains 2915 fps This just had a slightest shadow of extractor mark. Basically out of capacity also.
Fed 215 primer Hybrid 100V
72.0 grains 2922 fps
I have used 100V quite a bit and had a good idea where to start which seemed right on. This seemed like no more pressure than where I stopped with other powders.
Fed 215 primer IMR 4451
71 grains 2852 fps
72 grains 2860 fps
73 grains 2905 fps pressure didnt seem bad but has to be close to top
I'm going to concentrate on groups when I get a chance next and possibly try another powder or two. Can't wait to try and smash a spring bear with this rifle since it missed my elk season this fall.
So far I have basically just been able to run pressure tests, with very little accuracy testing, using the 250 grain Berger, 265 grain Long Range Accubond, and the 285 grain ELD-M. Powders tested so far include RL 26, N555, RL 16, Hybrid 100V, and IMR 4451.
Disclaimer: All loads with RL 26 and 285 ELD-M and 265 LRAB used a drop tube and with bullets seated .005-.010" off lands. 250 Berger was seated .080" off. All speeds taken with Magentospeed. These were just pressure tests in my rifle an not to be taken as load data. I stopped at pressure signs that were obvious to me (extractor marks, extra bolt lift, cratering or flattening of primer).
285 ELD-M Fed 215 primer RL 26
72 grains 2635 fps
73 grains 2666 fps
74 grains 2706 fps
75 grains 2747 and 2735 fps
75 grains was max pressure and capacity. Only the faintest shadow of an extractor mark
265 LRAB Fed 215 primer RL 26
74 grains 2741 fps
75 grains 2770 fps
76 grains 2807 fps
77 grains 2845 and 2856 fps
77 grains was also max pressure and capacity. Faint shadow of extractor mark but harder bolt lift
250 Berger Fed 215 primer RL 26
79 grains 2987 fps
80 grains 3013 fps
Both these loads were hot. I will post a picture of the 80 grain load case head. 80 grains was excessive and 79 grains is where I would normally stop and go 2 grains lower to start playing.
Fed 215 primer N555
72.5 grains 2758 fps
73.5 grains 2780 fps
74.5 grains 2810 fps
I could have possibly fit 1-2 more grains in but basically out of capacity. Didn't pressure out.
Fed 215 primer RL 16
69.5 grains 2791 fps
70.5 grains 2811 fps I made a jump to find pressure next.
73.5 grains 2915 fps This just had a slightest shadow of extractor mark. Basically out of capacity also.
Fed 215 primer Hybrid 100V
72.0 grains 2922 fps
I have used 100V quite a bit and had a good idea where to start which seemed right on. This seemed like no more pressure than where I stopped with other powders.
Fed 215 primer IMR 4451
71 grains 2852 fps
72 grains 2860 fps
73 grains 2905 fps pressure didnt seem bad but has to be close to top
I'm going to concentrate on groups when I get a chance next and possibly try another powder or two. Can't wait to try and smash a spring bear with this rifle since it missed my elk season this fall.
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