Heat effects on IMR 4831 vs SR4759 or max loads vs reduced loads in hot weather

[clearwater]

It was hot today, approaching 100 F. Using a 25-270 at 100 yards I shot 3 different bullets using the same charge of IMR 4831. 117 Hornady Round Nose, 87 grain Sierra and 75 grain Hornady at 50 grains. Usually these all get about 3/4", 3 shot groups. Today was 2 to 4 inch groups! Noticed the barrel heated quickly so cooled between each 3 shot group.

Then moved the target to 50 yards to try out a reduced load for small game. Dang if it didn't put 3 in 1/8"! I am thinking the barrel wasn't changing temperature so rapidly? Sure wish they hadn't discontinued 4759. Have about half a bottle left.

Know of any good replacements for I 4759 for 25-06? Don't get me started on TrailBoss.

 

[Joec7651]

I’ve never had IMR4831 show any difference on target from hot to cold. Every rifles different. Its obvious it likes the light load very much.

 

[clearwater]

I looked up best group from February when it was 5 degrees F (bottom). Next to best group yesterday.(Top)
I think that full power loads warm up the barrel quickly. I don't think it is the powder itself so much.

 

[JD338]

Good visual right there.

JD338

 

[wvbuckbuster]

Seems like a big increase in group size. Is it possible that something else might be going on as something loose? Was these groups from the same lot of loads? Just curious. Dan.

 

[clearwater]

Seems like a big increase in group size. Is it possible that something else might be going on as something loose? Was these groups from the same lot of loads? Just curious. Dan.

Same lot of loads. The small group with the reduced load was fired after the larger full power groups, tho I had let the barrel cool. (finally got to watch my friend shoot his 33 Winchester we had created loads for, but that is another post). The only variable I can think of was the temperature. The barrel got almost to hot to touch after 3 or 4 full power rounds. It's a standard hunting barrel on a 100 year old springfield action. Not pencil, not bull.

 

[TackDriver284]

Have you run those rounds through a chronograph? Did those cases show any signs of pressure?

 

[RL338]

For reduce loads , Blue Dot is what I use.

 

[clearwater]

Have you run those rounds through a chronograph? Did those cases show any signs of pressure?

No signs of pressure. Only have velocity from moderate temps and it was a bit low for the charge, I think because I use 25-06 data for the slighter longer 25-270 cases. Leaves me thinking that in hot weather I really need to make that first shot count.

 

[clearwater]

In looking thru my targets from last winter I came across a reduced load that worked well on a couple of groups with IMR 4227 I had forgotten about. 50 yards, without changing the scope sighted for longer range full power loads is the goal.
Misc primers and dropped from a lee powder measure not weighed, apparently I was just using up some odds and ends but it looks promising. Will have to weigh and sort powder and bullets and try again.