Load tested in HOT weather and Hunting in Cold weather?

[MajorSpittle]

So I worked up some loads and tested them while the temperature was 95 degrees.

I found an accuracy node that goes from 61.1 - 61.5 grains with Velocities of 2975-3000 respectively.

Normal hunting Temperature is about 40 degrees.

My initial thought was to split the difference and load 61.3 grains to minimize any variations I induce with brass size, primer charge, powder charge.... BUT I am now wondering if I should load at 61.5 grains to account for a possible velocity drop when hunting in cooler weather (I don't know how temperature sensitive the powder is, Hodgdon Superformance)

So the basic question is, Does the powder charge mean everything for accuracy or Does velocity? If I loaded 61.1 gains with velocity of 2975 while hot and the velocity I see at 40 degrees is 2930 can I expect my group to change and be more consistent with a group with a lower powder charge when it was hot?

I would theorize that 61.5gr @ 95 degrees has the same chemical energy as 61.5gr @ 40 degrees but the burn rate changes to cause the difference in velocity?

But how do you experienced loaders deal with this?

 

[LongBomber]

I try and develop my load on the top end of the node when its hot out, and on the bottom of the node in the winter. From the bit I have seen you want to keep the velocity inside the node with the temp changes.

 

[Don A Parsons]

I load charges so my primers are flat in the summer time when it's hot, don't change the load from that point on.

Most rifle barrels could have 3 too 7 nodes, if I find I loose my flat line of hits on paper, I start loading down, that way I'm not over pressuring the case/ chamber.

Hodgen powders help alot with their "Less temperature sensitive powders."

Your on the right track.

Don

 

[WeiserBucks]

Take several of your loads to the range after leaving them in the fridge overnight. Put em on ice for travel and see how they perform. You'll find out quickly if you have a stable load or not .

 

[Dosh]

Spittle, here in the Az desert with temps around 110 we can't attempt load development. We kill two birds with one stone. We go to northern Az at 6500' elevation and escape the heat. We all usually are drawn for hunts at that elevation and it's in the low 70's for a high with mid 40's lows. Actually going this weekend with 4 friends to shoot loads for 12 calibers.

 

[Fin-addictions]

Your powder plays a huge role in this. What powder are you using. At 90 degrees, they'll all gain some speed, but the temp stable powders will change less from 90 to 40 degrees. If you're using a temp stable powder you have a leg up.

If it were me I'd work the load up now, but check it when the weather cools to make sure I'm in the same velocity band. It might take a small tweak, but if you loaded at the high end now you should be close if your powder is stable.

 

[MajorSpittle]

Your powder plays a huge role in this. What powder are you using. At 90 degrees, they'll all gain some speed, but the temp stable powders will change less from 90 to 40 degrees. If you're using a temp stable powder you have a leg up.

If it were me I'd work the load up now, but check it when the weather cools to make sure I'm in the same velocity band. It might take a small tweak, but if you loaded at the high end now you should be close if your powder is stable.

I am using Hodgdon Superformance. I am not seeing anything about temperature performance with this powder.

 

[North Idaho Hunter]

i have read that superformance is not temperature stable.

last week I tested the temperature sensitivity of reloader 22. I stuck 3 rounds in the freezer, then popped them into an cooler full of ice. shot them at 85* down to whatever temp the froze ones were and only dropped 30 FPS.

I suggest you do that with your loads to determine the drop in temperature, if not, your just guessing.

 

[TwoMore]

I hunt in the south where it is upper 90s in the summer and I shoot all summer and winter. winter can be in the 20s sometimes here, I load for the season which usually means I am a tad different from winter to summer on loads, I mainly shoot H1000, RL25, RL33, wc872. I try to keep my velocity the same all season but even there the POI changes from the air density so I usually am about a minute low in the winter

 

[MajorSpittle]

Thanks for all the great info. I will stick some round in the cooler next time I hit the range. I have an IR temp gun so I can hopefully get them right around 40 degrees and some relevant data for hunting season.

I will also need to pay attention to not cooking rounds in the chamber while testing loads. I always try to minimize the time they spend in the chamber but I know while it was hot out my barrel was too hot to hold at the end of a 10 round string. I am sure the rounds at the end had to been heated to over 140 degrees after sitting in the chamber 20 seconds.

I guess that is the next thing I need to do, chamber a round in the hot rifle for 20 seconds, unload the round and check its temperature.