Maven
11-02-2015, 04:32 PM
It's been quite awhile, i.e., not since July 4 '15, since I fired my SKS mostly because I wanted to chronograph several different charges of IMR 7383, but the machine wouldn't cooperate. Today, using a ca. 1997 Shooting Chrony F-1, I was able to get readings with 22.8 gr. IMR 7383 + Win. LR magnum primers and 17.0 gr. IMR 4198 + Win. LR standard primers, both loaded with NOE 316-160 SP (gas checked, Ed Harris design). OAL was 2.125" and said CB was sized to .3155".
22.8 gr. IMR 7373 + Win. LR mag. primers -> 1,508 +- 17 fps; ES = 51 fps (n = 15). This was a mildly compressed load, which ejected well enough, but which left the [fired] cases sooty and unburned powder in the magazine well. Accuracy seemed to be on a par with Blue Dot and Unique loads I've tried, but the low sun made precision shooting problematic.
17.0 gr. IMR 4198 + Win. LR stand. primers -> 1,508 +- 28 fps; ES = 71 fps (n = 10). Ejection was vigorous with no sooty cases or unburned powder. I think I'll reduce the charge to 16.5 gr. next time to try to control ejection. I didn't test this for accuracy, but I'll bet it will group well. Btw, the muzzle blast was greater with 4198 than with 7383.
I'm sure you're wondering why I chose the ever quirky IMR 7383 for so small a cartridge as the 7.62 x 39mm. I did so for several reasons, not the least of which was the absence of more appropriate powders such as IMR 4198 and Alliant RL-7 locally. (I got #1 of each later, after I began testing 7383 in the 7.62 x 39 cartridge.) The other reason is that I have ~1/2 of a #7 jug of 7383 left and I wanted to experiment with it in that cartridge.
22.8 gr. IMR 7373 + Win. LR mag. primers -> 1,508 +- 17 fps; ES = 51 fps (n = 15). This was a mildly compressed load, which ejected well enough, but which left the [fired] cases sooty and unburned powder in the magazine well. Accuracy seemed to be on a par with Blue Dot and Unique loads I've tried, but the low sun made precision shooting problematic.
17.0 gr. IMR 4198 + Win. LR stand. primers -> 1,508 +- 28 fps; ES = 71 fps (n = 10). Ejection was vigorous with no sooty cases or unburned powder. I think I'll reduce the charge to 16.5 gr. next time to try to control ejection. I didn't test this for accuracy, but I'll bet it will group well. Btw, the muzzle blast was greater with 4198 than with 7383.
I'm sure you're wondering why I chose the ever quirky IMR 7383 for so small a cartridge as the 7.62 x 39mm. I did so for several reasons, not the least of which was the absence of more appropriate powders such as IMR 4198 and Alliant RL-7 locally. (I got #1 of each later, after I began testing 7383 in the 7.62 x 39 cartridge.) The other reason is that I have ~1/2 of a #7 jug of 7383 left and I wanted to experiment with it in that cartridge.