Ammunition & Velocity – Hot vs. Cold Car

Nathan S
by Nathan S

Its commonly understood that ammunition that is hot will propel a bullet to a higher velocity than those at colder temperature. In fact, the 1:7 twist rate for the M16 was chosen to be able to stabilize the tracer round at sub-arctic temperatures.

The Wound Channel did a short experiment using ammunition left in the hot sun versus those kept in an air conditioning vent. The difference of only 100 degrees is nearly 100 FPS, which with a 5.56 can be a major difference in lethality, especially at longer ranges. Its good news for our boys in the Middle-East who are plagued by high temps and something for them to look out for when up in the Afghan mountains.

Nathan S
Nathan S

One of TFB's resident Jarheads, Nathan now works within the firearms industry. A consecutive Marine rifle and pistol expert, he enjoys local 3-gun, NFA, gunsmithing, MSR's, & high-speed gear. Nathan has traveled to over 30 countries working with US DoD & foreign MoDs.The above post is my opinion and does not reflect the views of any company or organization.

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2 of 17 comments
  • The Wound Channel The Wound Channel on Sep 10, 2015

    Thanks so much!!!

  • W.P Zeller W.P Zeller on Sep 11, 2015

    Actually, certain pistol powders go slower when hot and faster when cold.
    Specifically, Winchester Super Target is notorious. Those near-max loads made back in June can be very stressful if fired out on the range in January.