Developing loads over winter...bad idea due to pressure?

[Pdvdh]

Here's IMR 7828 and Hodgdon Retumbo and H1000 in three different cartridges. Velocity was recorded over duplicate chronographs (Oehler 33 & Pact PC2) or triplicate chronographs (Oehler 33 & Pact PC2 & Oehler 35P) run concurrently with each bullet fired.
Tract 1 is Retumbo in a 7mm Rem Mag with a 168gr Berger VLD. Barrel length = 24 3/8".
Tract 2 is IMR 7828 in a 300 Win Mag with a 210gr Berger VLD. Barrel length = 25 1/2".
Tract 3 is H1000 in a 280 RCBS Improved with a 162gr Hornady Amax. Barrel length = 28".

Retumbo least temp sensitive. IMR 7828 most temp sensitive.

 

[Pdvdh]

When I temp test, both the ammo and the rifle are brought down to outdoor temps. Not just the ammo.

 

[memtb]

Deleted!

 

[memtb]

When I temp test, both the ammo ad the rifle are brought down to outdoor temps. Not just the ammo.

This!! memtb

 

[86alaskan]

I'd be cautious if you think the temps will swing very far. My 308 AR10 load with 168 SMK and IMR4064 is fine right now. But... when I shot it this last summer at 95F I was cratering primers, way over gassing the gun and getting all kinds of fouling into the upper. Just shot it again recentlyat 40F, none of those problems were present, so I'll probably try varget this summer for a more temp stable load.

 

[Pdvdh]

If I didn't develop loads in cool temps, I'd rarely have an opportunity to work up loads.

 

[86alaskan]

If I didn't develop loads in cool temps, I'd rarely have an opportunity to work up loads.

I felt your pain for awhile when I was in anchorage. I don't think the range ever got over 70deg even when it was hot. But there were plenty of times I was working on loads around 0F.