Temperature sensitivity with H-4227

[gr8ful]

During a rescent range trip with my contender, I had a box of 256 Win Mag reloads sitting on the bench in direct sunlight while I was shooting my 7mm TCU, after changing barrels my first two shots with the 256 resulted in blown primers.  I immediately stopped shooting and descided to scrap whole batch of ammo figuring I had made some kind of BAD mistake.  Well today I finally got around to pulling the bullets and descided to weigh the charges to check for errors, all were 14.5 gr, well below Max for H4227 and 75 gr bullets in any of my manuals.  This is a proven load in my barrel and the only variable that changed was that the loaded cartridges were warm from being in the sun.  Also, I reassembled a few with the same components and got no pressure signs.  Has anyone else ever experienced anything like this?

[Larry Gibson]

"sitting on the bench in direct sunlight"
That was your mistake, not the load.  Doing such is a common mistake and is one that should not be done.  many writings, instructions and manuals have admonishments not to do same.  Keep the ammo covered up and out of direct sun light.  That can easily happen to all or any ammunition regardless of the powder.
Larry Gibson

[us920669]

Yes, it bakes like a closed car in Tucson.  That's why people should be careful taking hot loads to Africa, especially the high-pressure numbers.

[gypsyman]

I've found that lower loads with 4227 doesn't seem to be as sensitive as when you get close to max. gypsyman