I haven’t shot my gun for a good 11 years (on a black bear) till the other day. It’s a model 700 I bought new around 1999’ chambered in 300 rum. It has a timney trigger set a 2 pounds. Been in it since the day I bought it. Never had any hang fires ever with it till my range session the other day…and this morning. I could feel the pin strike and a fraction of a second later boom! It isn’t always, but random. I am using a 180 grain speer round nose with Speer’s suggested minimum charge of 81.1 grains of IMR 7828 SSC powder loaded at 3.350”. I am using CCI 250 magnum rifle primers and Remington brass. Some of the brass was given to me and about 13 of the necks cracked after the first range session yesterday. I have two pieces that didn’t crack but the necks must be so thin because the bullets slide loosely after seating. The remainder of the brass was new. I tumbled my brass and let dry for a few days so I figured there wasn’t moisture in the cases. Some of the brass has been shot several times. All were annealed before these firing sessions. I set the shoulders back .002” to .003”. Primers we’re all seated below flush. Some of the primers did go in easy. I removed the action yesterday and sprayed everything down with Rem oil after cleaning the barrel. It does that the goofy J lock on the bolt. I didn’t take the bolt apart to clean the inside of it yet. The firing pin hole doesn’t have any build up around it and looks pretty clean. Any suggestions besides bolt disassembly and cleaning? I know that j lock pin assembly should be replaced. I am on the look out for a stainless one for my 300 and blued for my 375.