Can anyone tell me if cold winter temps can cause erratic muzzle velocities of say 30-40 fps. This load was developed during 70 F temps with little variation in fps and now in the low 30's I'm having these swings. THANKS

Possibly..

Shoot enough with a chronograph and you will find that many things affect bullet speed, not just temperature. Same load, different day, different speeds. The higher the speeds seems to give more difference in speeds. When my .416 Rigby gives a 40 fps difference in speed at 2400 fps, it gives me more to think about than when my .270 WSM gives the same speed difference at 3400 fps, if that makes sense. Good shooting.

quote:

Originally posted by craigcampbell:
Can anyone tell me if cold winter temps can cause erratic muzzle velocities of say 30-40 fps. This load was developed during 70 F temps with little variation in fps and now in the low 30's I'm having these swings. THANKS

Yes, absolutely. That is why I mainly use Hogdon extreme powers when I can. Also, the higher the cartidge operating pressure the worse the problem gets.

You could try this: Keep your cartridges at uniform temperature (under your coat?). Shoot two or three shots to warm the barrel, then shoot your group leaving each round in the chamber the same amount of time before firing. You will most likely see less velocity variation.

Regards

There is no question that temperature extremes, among other things, will effect velocities and performance.
That is why loads should be developed as close as possible to the climate that they will be used in.

When I develop a load for say, antelope hunting or digger shootin, I will wait for summer days because I know that when I do that the days are warm.
Like-wise, when I develop a load for Elk hunting, I will do so on a cold day in winter.
Whenever I develop a load I do so with a temperature scenario in mind.

Developing loads in this way just takes one major variable out of the equation. The variables we have to deal with as it is are enough.. Why add more?

well i can tell you for sure that the temps here have sure screwed up my velocities and performance - supposed to get to +20 this week - that will seem like a heat wave