Cold Weather Load Development

[Shiloh]

What can one expect when chronographing loads in 40 degree weather??
Is there a standard "Rule of Thumb" for increase and decrease in velocity based on varying temperature scenarios? I have a load for a Krag cut-down that consists of
a Lyman 314299 sized at .311 set on top of 16 grains of surplus 4759.

The Lyman book says that 15.5 gr of cannister 4759 for a Lyman 311284 is 1426 with the boolit sized to .309. Any idea what the standard temperature is for loads printed in the various loading books? Any idea of one can expect for the same load at 80 degrees??

Shiloh

[jonk]

Good question! I just shot some 6.5X54 using a Lyman 140gr mold and 13 gr of 2400. This combo was never a real tackdriver, but a fine plinker in the summer. Same gun, same load- tumbling and keyholing in the winter.

[threett1]

I believe the general concensus is to expect more pressure at elevated temperatures. It is best with temp sensitive powders to work up max loads in warm weather, then they will be safe in cold. With the advent of temp insensitive powders, like some of the Hogdon series and Western's Ramshot brand, this seems to be more forgiving. Personally have no experience with the number you are using. I'm sure some of the brethren here can enlighten on that.

[Shiloh]

It was about 45 degrees when I got to the range. Sunny so it was nice.:-D
I had the Krag ammo inside my coat to keep it warmer than the ambient temp.
I fired one string of each load over the Chrony Beta at 50 yds

16 gr of surplus 4759 gave:

AV 1483 ES 57.53 SD 16.09 about 2.25 inches for 10 shots 2 flyers, 1901 rear sight at 300 yds was 4" low

17 gr gave:

AV 1531 ES 25.26 SD 8.00 10 shots was a little bigger group but the bulk of them were in the 2.25 area with 3 pairs of shots touching. Shows promise. Rear battle sight at 400 yds had mostly 9's a few 8's 3 X's on a 25 yd slow fire pistol target at 50 yds

I'll try both loads again when it gets warmer. That will give an indication of how much the velocities will go up. I invite input from those who may be able to educate me on the higher temperature estimates of increased velocities.

Shiloh :castmine:

[Bass Ackward]

Some powders in some applications show little change. Same powder that is manufacturered to be temperature insensitive, in something else can be vastly different. The likelyhood that it will be dangerous is really small, or it wouldn't be in print.

I have an old friend that loves the old surplus H-4831 in his 270 with a 130 bullet. He brags and brags and brags on it. He worked his load up in the fall before hunting season and was just over 1/2".

In the summer, he has a hard time holding 1 1/2". He can't figure out why I always know when to set the money on the table. :grin: It drives him nuts thinking it's always him when the chips are down. I always buy him something as a gift with his own money to live with myself and I swear, one of these days, I am going to let him in on the secret. :grin:

Always test to be sure.