Chronographing in cold weather

[Target_in_sight]

I ran the same load through the chrono but twenty degrees colder than when I developed it and velocity dropped about 60 fps.

My calculated drop at 300 yards was suddenly off by more than I was willing to accept. That's not a rounding error, that's a miss. Temperature affects powder burn rate and burn rate affects velocity. It's not theoretical. I watched it happen on the chrono.

So know your load at the temperatures you'll actually be shooting in not just the ones you load in.

 

[Jason1]

That’s a solid confirmation of why dope built in warm weather doesn’t always translate. Cold temps exposing that 60 fps change is exactly the kind of gap that shows up at distance

 

[Bulb]

I ran the same load through the chrono but twenty degrees colder than when I developed it and velocity dropped about 60 fps.

My calculated drop at 300 yards was suddenly off by more than I was willing to accept. That's not a rounding error, that's a miss. Temperature affects powder burn rate and burn rate affects velocity. It's not theoretical. I watched it happen on the chrono.

So know your load at the temperatures you'll actually be shooting in not just the ones you load in.

That’s the kind of real-world data too many reloaders ignore until it costs them a clean hit

 

[Dexter]

Cold weather can noticeably reduce velocity and shift impacts. Always confirm chronograph data in the conditions you’ll actually shoot in to avoid surprises at distance.

 

[Alan]

Temperature can have a huge impact on velocity especially with certain powders. Seeing a 60 fps drop on the chrono isn’t surprising and testing loads in the conditions you’ll actually shoot in is the only way to trust your ballistics at range.

 

[sixth_sense]

I never thought to check how temperature affects velocity until a buddy mentioned it at deer camp. I just assumed a zero was a zero but apparently, that’s not the case.