Badly fouled/coppered bore - perhaps hot as well = pressure jump. Hot ammo - sitting in the sun can increase the powder temperature to where it developes extremely high pressures and then pierces primers. The Ruger is a modern high pressure round that is developing well over 60,000PSI- maybe 64,000SPI - probably. It is a small step upwards to where primers 'pop'.

I suggest you remove the bolt and inspect it and the firing pin's nose carefully. When primers pierce, a jet of extremely hot flame plays on the tip of the firing pin and around the pin's hole on the suface of the bolt face. This jet of flame is like a miniature cutting torch.

This flame can roughen, cut away metal and sharpen the pin's nose which then increases the chance of piercing normal pressure loads. Too, the bolt face can be badly cut by the gasses as well, which can cause primer cup extreusion into the cuts which increases difficulty with rotating the bolt to extract cases. It sometimes takes very few 'pierced primers' to do this much damage. Sometimes only one.

I've seen a blown primer cut a narrow groove all the way across a bolt face. You would think only the softer brass would be cut - not so. The culprit was a rough and slightly pointed pin in an old 98 Mauser action, re-barreled then test fired. A factory .30/06 load pierced the primer.

Sometimes faulty primers get past quality controls and are sold or loaded by factories. I've seen it happen a number of times with small rifle primers. Faults can run from too-soft cups, to too-hard cups and everything in between.

That some ammo pierced while some didn't, points possibly at the primers as both loads would have been loaded to the same factory levels. The ammo can be the same lot, but the primers might not be, just as the powder might not be.