High VS Low temperature reloading

dcloco

What are the problems when working up loads in the summer versus the winter months?

Highball

Using the Extreme line of powders...not a lot.

The old time powders exhibited quite a bit of sensitivity to temperature variations....

Winter loading that were loaded 'hot' for 20 degree weather will often blow primers at 100 degrees next summer..I have had it happen.
Summer loadings will show as much as 200-300 fps slower velocities next winter.

The effects change with the different powders...and it is difficult to predict across the entire spectrum what will happen...the above is a generalized viewpoint of effects.

sandwarrior

dcloco,

+1 on what highball said. I've had 400 fps difference with standard powder. Most notably with my favorites, IMR and Hodgdon 4895.

I've had such success with extreme 4350 this past winter and summer testing loads that I went and got 8# of the extreme 4895. I used same loads(4350) from -18F to +96F and got a maximum difference of 20 fps avg. That was loaded in three different cartridges, 7.5x55 Swiss, 7.65x53 Argentine and .257 Ackley imp. I have just started loading the summer tests for the H4895 extreme.

Conversely, I've generally only had about 100 fps difference from summer to winter with Vihtavuori powders. Again, these are temps from -10 or so up to +90 deg. In comparing cost effectiveness between the two I've found extreme and VV to be about equal. I get very good pressure form the VV, so it has generally taken a little less powder to get the same velocities as Hodgdon...generally, that's not a hard fast rule. -anyhow, hope that helps

Highball

I have had great success with Varget. Less then 50 fps...and pretty good accuracy, also.

JustC

varget and the hodgden extreme powders as well as vihtavouri are less temp sensitive. The advances made in the coatings of the kernals, is what has led to temp stability. By controlling the burn rate, the temp becomes less of an issue. That is what little info I have compiled.

I know a lot of the ball military powders were very temp sensitive due to their small size and lack of newer coatings. Like H870 would make a great summer load, but then fired in the winter would be slow and dirty.

dcloco

Thanks. I am working on an 8# jug of H4895 - from 1973, followed by two 1# cans of H4895 from 1983. Just wanted to make sure I was not going to run into a problem.