300 RUM pressure signs only after 10 rds

[tgrose]

I have a savage 112 in 300 RUM with the factory magnum contour barrel that I have been shooting my pet load of 93gr retumbo with 208 gr Hornady amax. I have been shooting this load for 200+ rds over a couple of years now with no problems and excellent accuracy. I have always shot 5 rd groups and allowed time between groups for the rifle to cool to be kind to the throat and minimize erosion. I just recently put this combo into competition at the long range challenge at peacemaker national training center. This match incurs 15 shots in a couple of minutes. After about 10 rapid shots the bolt started to become sticky and the primers were starting to have some cratering I have never seen before. Is the heat in the barrel causing this?? I plan on dropping down to 92.5 gr for future loads. I was considering reducing the OAL of the already loaded cartridges by a few ten thousands to reduce pressure. Any other thought or ideas would be appreciated.