I was at the local gunsmith's place shooting the breeze when he showed me a PF M70 a guy brought in. Seems the guy put a 270 Win round into the rifle which was a 7mm RM and fired it. Some part of the top of the bolt head was ruined and the cartridge case was black at the back end with a big, open crack about a third of the way of the spent cartridge case. The gunsmith said when he put the 270 cart back into the action it wouldn't even fit all the way into the chamber. He did it again with a new, unfired 270 cartridge case and same thing.

Since I don't understand it all can someone explain basically what happened when the guy loaded the wrong cartridge into the rifle and fired it please? Thanks.

The case attempted to expand to fill the chamber and split before it could seal the chamber. When it split it poured high pressure gas out the split and into the bolt face and action.

got a browning auto in 7 mag inthe shop now that the guy fired a 270 in it. mist be the new fad

In 2010 I had two rifles on the shooting bench:
a) 1956 M70 270
b) 1977 Ruger #1 7mmRM

I managed to fire a 270 handload in a 7mmRM rifle twice:
a) a wimpy load
b) a hot load

Damn my 280rem shoots 270win into 6" groups. I was wondering what the he'll happened to my rifle.

Transgendering the thing is a bitch, ain't it?

When they changed the name of the .280 Remington to 7mm Express there were lots of those fired in 7 Remington Magnum rifles. I was working in the Browning Arms gunsmithing shop at the time and repaired quite a few BAR rifles that suffered this fate.

One of the wife's cousins shot a 270 win.in a ruger chambered in 7mm.

Bowed the floorplate and busted the stock real good.

He however survived with some cuts and splinters,along with some soiled pants.

Last time I was at my gunsmith's place he had a Remington 700 chambered in 270 Winchester. The owner mixed up his ammo and shot a 308 round in it. The rifle was in parts, and the shooter had some damage, too.

Shoots like a 77, then?

Years ago, while in grad school, I worked in a Woolco sporting goods department. One of my fellow workers sold a guy a Marlin 336 in .35 Remington and a box of .30-30 ammo, because everyone knows that Marlin 336s were only made in .30-30. Needless to say, right after the customer's first visit to the range, he was back and sputtering and foaming at the mouth angry. We accepted return of the rifle, the fired case (which had expanded and ruptured as expected) and the remaining 19 rounds of ammo and refunded his money. Then my boss put the rifle back on the shelf, sold the partial box of ammo at a reduced price and told my knuckleheaded co-worker what a moron he was and how to identify the cartridge for which the rifle was chambered. Shortly afterward, I graduated and that was the end of that. Not too long after, Woolco went into bankruptcy and disappeared.