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Recently, I mentioned having bought some cast 8mm Mauser rifle bullets from Bill Benny. Today, I took some loads to the range that I had put together to try out the bullets. The bullets were 169 grain RNL with gas check, lubed with Lyman Super Moly lube. The loads tested were:
169 gr. RNL GC bullet
25.0 gr. H4198
WW LR primer
RP brass
Average muzzle velocity 1793 fps
Standard deviation 24.76
Very accurate
169 gr. RNL GC bullet
25.0 gr. IMR4198
WW LR primer
RP brass
Avg. muz. vel. 1860 fps
Standard deviation 15.36
Very nice accuracy
If you wonder why I would try identical charges of Hodgdon 4198 and IMR 4198, this was to test the relative velocity of one against the other. My H4198 is over 30 years old, and I have long suspected that because of its age, it didn't have quite as much energy content as the new IMR4198 that I have. The chrono results seem to bear this hunch out. I have to add that the accuracy obtained from the loads using H4198 was a little greater than those assembled with the IMR4198, at least in my hands.
Another load tried this date:
169 gr. GC RNL bullet
20.0 gr. SR4759
WW LR primer
RP brass
Ave. muz. vel. 1805 fps
Standard deviation 9.18
Accurate
SR 4759 is a powder designed for reduced charge and lead bullet loads. It has been one of my favorites for many years. With the above load, the accuracy was good but not quite as good as the two loads using 4198 powders. Sometime in the future, I will tweak this load one grain in both directions to see if I can tune it a bit.
The rifle used to fire all of the above loads was a Remington Model 700 with optical sights.
Before I fired these loads, I elevated the barrel slightly to get the powder over the primer. These are all reduced charges for this caliber, and do not occupy anywhere near all the case capacity. Remember, 19.5 grains of H4198 nearly fills a .222 Rem case, so you can get an idea how much empty space is left in an 8mm Mauser case when charged with 25.0 grains. According to my experiments with the chrono, you can lose 75 fps in a typical milsurp rifle cartridge by firing reduced charges with the powder forward in the case rather than toward the back, over the primer. In a practical shooting situation, you don't need to think or worry about this, because it's not going to make that much difference on bullet impact with "practical" sized targets. When you are checking speed on a chrono, I like to be as consistent as possible from shot to shot so I do it as described above.
Some shooters of reduced loads like to use fillers to take up the empty space, but there are undesirable situations that can result from that and I don't want to get involved with them.
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