Quote Originally Posted by earl39 View Post
You are at the bottom of the Hodgdon loading range (41.5 being the starting load) so you could have a light load high pressure deal going on. With the added heat the load preformed better and now you are getting more of an explosion instead of a burn. Speaking just for myself I would try a single round loaded 1/2 grain heavier.

http://www.hodgdonreloading.com/data/rifle
But with LC brass you have to reduce loads by 10%. I made this mistake ONCE...my brass came out in two pieces, and the bullet soldered the jacket in the barrel, when I started with a medium load (I know...I was young and dumb!).