Is temp. sensitivity a key factor in choosing a powder for hunting? I hunt in Northern Minnesota and during Deer Hunting season temps. can range from 50 above to 20 below. When a powder is temp. sensitive, what goes bad and how bad? I know velocities can decrease with a drop in temp., and maybe the point of impact will change, but, can a carefully worked up load go completely to hell and not group for shit in extreme conditions?

I know if you work up a load in cold weather thats close to MAX when it gets hot you might be in trouble. I doubt that it would really make enough difference to cause problems but stranger things have happened I suppose. I try to stick with powders that are more stable like varget and such. I think the ball powders are normally more temp sensitive than extruded of flakes are but Im kind of new to this also.

Temp changes do affect you loads, but some more than others. Hodgdon is obviously a good way to go and even with all the hype about Reloader powders being extremely temp sensitive, I took a few rifles out to Colorado with me last year during November when it would get real real cold at night. I didn't see any change in my groups whatsoever or my POI. All 3 rifles were stuffed Reloader powders and all the loads were worked up in August and Sept. in Ohio before the trip. Go figure. I've seen a bigger problem with elevation differences from state to state over temp changes in the same area.

I have only done very limited experiments, but there is a limit on the effectiveness of extreme powders. They DO reduce the change in velocity (pressure) due to a change in temperature. No doubt about it.

Problem is, the groups as well as POI still change in the guns I've played with, when the temperature changes substantially. My conjecture is that the harmonics of the steel in the barrel and action change, with temperature, but I don't know.

I use temp stable powder, but I don't believe it solves the temperature problem by itself. There are other dimensions to it. JMO, Dutch.

Great topic. I'm using H414 in my 7mm-08 and was wondering about temperature problems too. To get similar size groups from H4895 I loose about 140 fps, I have not had any luck getting Varget to group worth a damn and I can't get 4350 up to velosity without compresssing the load so much that the bullets actully move in the cases overnight. In North Florida (In Fl you have to go north to get south), I can be hunting in 70 degree weather one day and 20 degree weather the next. I work up my loads in the spring & fall and try to find days in the 60's & 70's to do that. I have check these loads over a chronograph in mid 80 degree weather and have found small increases in velosity, usually no more than 20 fps but was wondering what happens when the temps drop. Guess I'll have to wait for a day in the 20's to go set up and see.

Let me see if I've got this right. If I work up a load in hot weather then shoot it in cold weather, I can expect some vel. reduction and maybe POI change. But the load will still be "The Load" worked up for that rifle, only slower and off zero. Reset zero and I am good to go,Yes? If I work up a load on cold or cool weather, watch out if I shoot the SOB in hot weather,Yes?

Thanks Steve

I used to own a house in MN as well as AZ and shot year round. Still do in AZ, but the extremes are obviously not great.

I switched to Extreme powders exclusively for long range guns. Varget is especially good. Ball powders are terrible, and IMR powders are not much better. I once chronographed Varget in a .308 at -20 and 105 and got 8 fps difference.

Even if the MV is the same, you have to add a bit of elevation as range inceases past 500 yards. The killer here is low BC bullets, which take a big hit when colder air is involved.

Which reminds me of favorite pet peeve: when shooting at an angle, one need only hold for the horizontal distance, as gravity only affects the bullet over the horizontal flight path. This is the biggest crock of crap ever repeated in print media. Okay, then why does a bullet fired at 0 degress F drop more than a bullet at 100 degrees F? The horizontal distance is exactly the same. Ans? Time of flight...