Im about to buy a 243 savage for coyotes.. My 6mm with wood stock went crazy on me this fall with the temperature decreasing. Dont know what it is, dont care, im moving up to a stock that wont move with conditions, heavier barrel, pillar bedding etc. Be fore i do that i want to check with your experience on what caliber, bullet and powder have you found to be the least problematic with temperature change. I dont know if you can get by without changing impact between 80 degrees and -10 below zero, but what have you had good luck with not having to change loads every 30 degrees, is there a sweet heart out there that helps with that? thanks dave (Im going to post this question in benchrest to get maximum viewing. I hope that doesnt break the rules..)

The biggest culprits in the shift in POI with the change in temp would be attributed to the powder, primer, and the stock. A good bedded freefloated laminate stock should be fine. The first powder I would look at for the 243 and temp stability would be Varget.

edited: I just looked at a can of Varget and the 243 isn't listed as one of the pet loads. On the other hand it is listed on H4350's can as a pet load and is mentioned on 6mmBR.com's 243 page. It looks as if it is a favorite for the mid to heavior bullets and I know that h4350 is stable at various temps.

Yes, there is a sweetheart out here. My sweetheart is a 500 Jeffery. It is non-problematic and in no way affected by temperature change.

quote:

I just looked at a can of Varget and the 243 isn't listed as one of the pet loads

But it is listed in Hodgdon’s reloading manual and is shown to be the top velocity producer for the lighter bullets. (H414 is near the top for most bullets weights). I seem to recall that both Varget and H4350 are specifically designed for 'temperature stability'. Open to correction.

The Hodgdon Extreme powders loose the least velocity of any powders that I know of .... So Varget ,h4895 H4350 ect will work as well as anything or better than most .......H414 and Win 760 [same powder] arn,t too temp stable ..... Most ball powders arn,t

free--float barrel is hugely important in my opinion

I purchased a Howa Axion in 243winmag last week------blasted a coyote with it earlier today.

synthetic stock and free floated heavy 24" barrel. Purchased it for the same concerns you have.

the Axion is a varmint rifle with great clearance between barrel and forestock.

.22 CB Short?

FWIW, I'm not sure what the LEAST sensitive is, but I've a pretty good idea what the MOST is.
I use an M98 Mauser with a .250x2(a .243 in .25cal, long neck and 40* shoulder) barrel @ 20" in a wooden, thumbhole stock. The action is bedded in glass, and has a freefloated W70-type Featherweight barrel. I've used it in Nevada, where I am now, and in Alaska, where I lived for several years. The temperature variation was 105* to -28*! I've had no problems...until I switched to BR cases. So I switched back!
WW748 seems to be what I want, and I've used about everything. By "everything," I mean 3031, 760, 2520, 4895(and H4895), 4064, 4320, H380, 4350, H450, and 2700. Most of my testing has been over an Oehler M33 chronograph, with 5' spread. The lowest temp I've chronoed was -5*, tho'.
Personally, I'd say that stick-powder, with a Magnum primer, for hot AND cold would be your best bet. The idea would be to use the same load all the time, eventho' it may not be the best load at any given time. I would use a CCI or Winchester primer, as I believe the Federal is a little too powerful for the warmer-weather use.
The Allient double-base powders MAY be slightly superior during the winter, and they are certainly good when it's warmer.
Have fun,
Gene

w748 is terrible in the cold .... I have had very good success with H4895 in some rounds , It is going to be the first powder I try in my 243 when I get it home ....... The Hodgdon web site shows it with all the bullet weights up to 107 grain ...There are some new powders that I havn,t tried like 100V and 780 Supreme . The Hodgdon Extremes are grfeat powders imo ........

In the rem 788 the h4350 seems to show some promise. Probably due to a complete workup in lower temps.. 42 grains of h4350 shot 13/16 inch three shot group at 100 yards in this light gun. and i did not use any other weights of powder up to 43 grains becous i didnt think the lowere pressures would work well. so that gives me something to work on.. It will do 1/2 inch in the hot weather with imr4350. the best news is i just ordered the savage model 12 varmit .243 low profile with stainless barrel and laminated stock, pillar bedding 1- 9 1/4 twist etc from jerrys.. Ill use the 788 for packing, the savage for short walks and calling with the new fox pro sceary, that has newest controles, that work with multiple changing frequencys im guessing like the cell phones, guarenteed to 200 yards, and has been used at the factory up to 900 yards.. Dont think ill be shooting at that range. more like 200-300 for critter shooting.. the sceary has room for hundreds of different calls, wolf, birds, and who knows whatall, that i wont be ablt to use.. and i can progame them in any sequence, with multiple speakers doing different sounds.. , I know you guys with one rabit call and two dozen coyotes this year already is laughing his butt off but i just want one!!!.. Im getting ready for the new wolf season!!! whenever those judges let it happen.... It raises the hair on your back when your out elk calling and one starts that long low howel.. Ill be putting my leopold 6 .5 x 20 with varmit reticle on the new savage.. So wish me luck and ill be back looking for loads during the breakin and load formulation stages.. Im looking for CONSISTENT impacts in different winter weather conditions, not so much the pea sized groups, so im hopping this is the one.. thanks for your input, dave