Our range LM's had a similar issue as we run every possible brand and type of ammo through them, HP 55gr no problem, Sako HP 45gr was a bit short and lead tip with slightly distorted, but never a failure to feed.

Slam fires usually occurred with older bolt assemblies, these usually had elastomer o ring that gummed up. We upgraded those to spring type and free floating pins, in addition we had a gunsmith machine the firing pin tip flat by approx 250 microns, so instead of a sharper point you now have what looks like a flat nose bullet. Never had an unintentional double tap or burst fire since. We use any ammo we can get, and the LM's run everything beautifully.