I have a Ruger Alaskan in 416 ruger. On the weekend I was out in an old quarry with my friend doing some load developement for a couple of varmint rifles we have. In between groupings we were firing the 416Ruger using up some Hornady 400gr factory ammo to get the cases for reloading and just having fun. We had fired around 55 factory rounds between us over a period of a couple of hours when suddenly the factory ammo started popping primers. We stopped using the rifle and when I got home I did a search on the internet for any similar problems.

There was a big bore user who said he had a similar problem with a big bore rifle and suggested it was caused by the build up of copper in the lead causing the pressure to rise to the point where the primers pop and he also suggested that the rifle should be cleaned more regularly.

As the rifle wouldnt under normal hunting situation have this many rounds fired continuously I wonder if he was correct. I have since cleaned the barrel and there was alot of copper in there. Since then I have fired another 10 rounds and no further problem .

My question is Has anyone else experienced this and is it normal for big bores or just this cartridge?