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Old July 11, 2017, 10:08 PM   #15
Jimro
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Join Date: October 18, 2006
Posts: 7,097
Quote:
All very good powder's in .308. Never shot in extreme heat or cold, so really can not say much about temp sensitivity, other than the military uses[or used to] RL#15 in their M118 sniper rounds because of very good accuracy and insensitivity to extreme temp changes.
Well...here is some history of M118LR using Reloader15, it was chosen because it was better than IMR4895 for accuracy pushing the 175gr SMK. There have been 4 powders used in the M118 series, IMR4895, WC750, Reloader15, and IMR4064, and they were used pretty much in that order. The problem with Reloader15 became very apparent in the "War on Terror"

Originally IMR4895 and WC750 were used with the 173gr FMJBT match bullet (same bullet used in 30-06 M72 match ammunition). With the switch to the 175gr SMK Reloader15 was chosen, then replaced with the M118LR Mk316 Mod0 which went with IMR4064 because it was much more temp stable. The biggest problem was M110 sniper systems were getting a lot of brass stuck in the chamber, essentially turning the semi auto sniper system into a single shot, which was not good.

The M118 series has also used two different grades of brass (Lake City and Federal for Mk316), as well as two different powders (LC milspec primers and Fed GMM primers). So between multiple sources of brass, primer, powder, and two different bullets, you can say that the military has been messing with the sniper ammo quite a bit.

Jimro
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