So - I kind of got a bit lost there. Are you having the same problem with the Hornady brass? I think it is unlikely your hammer spring or trigger, in general, has anything to do with it. If your rifle shot fine before (?) with other ammo and now is doing it with the Lake City and Hornady brass, what were you using before - or is this a first time shooting this rig? It sounds like you run into this issue with this rifle sporadically, regardless of brass? I ask, as if you have too much firing pin protrusion or an excessively long firing pin - this would be a very regular thing - like every shot, I'd think. I'm guessing you have either excessive headspace or the load is just too warm - or a combination of both. If only using the Lake City when this issue arises, I might be inclined to think that, because Top Brass reconditions brass shot in various rifle chambers, there is going to be varying degrees of spring-back on the shoulders. I'm not aware that Top Brass anneals their brass before loading - and if they don't that problem would exist a bit. But it isn't really a problem unless the shoulders were pushed back a bit too far. Some of the resulting sized brass would be softer, some harder - and the shoulder would end up with different setback range. The brass staying "true" to the die, holding the setback fully would be the rounds which may show the traits of excessive headspace, if that makes sense. A little too much headspace and a little warm on the load will combine to do what you have encountered. I'd be sure you are not bumping your shoulders any more than .003" from the LONGEST piece of fired brass, as measured form the shoulder to the base, using a Hornady tool or the like. Even then, your longest piece of brass may not have blown the shoulder forward fully. It is possible, with the excessive headspace, to have brass that looks like it is a really hot load - when not. I'd look at both of these items to see what is up. Good luck.
