.300 Win Ultra Mag question

Wait a minute, something is not right. Your gun is marked .300 REM ultra mag, not .300 WIN ultra mag. There is no .300 WIN ultra mag that I am aware of.

Post a pic of your fired cases. If you had shot .300 Win Mag cases in a .300 Rem ultra mag chambering, they should come out looking nearly straight. They certainly wouldn't look like they did going in.

Need more information.

Normally when you fire a case into a grossly oversized chamber, the pressure goes down. But not always. I'm surprise that none of the brass ruptured - good thing it was new and not old and brittle.

Fascinating little experiment, but don't be in a hurry to repeat it!

Neat picture. What kept the problem from getting out of hand, in my opinion, was that the bullet was probably reasonably well aligned in the throat when it went bang. And of course was the correct diameter. If the bullet doesn't get stuck, then the gas pressure just expands the case to fit the chamber.

The rifle manufacturers have to design the gun to handle a certain level of escaping gas, because case heads to let go from time to time. When pressures get pushed outside of the normal range (due to a bore obstruction or delayed ignition, etc.) is when bad things happen.

Thanks for posting the pic. Good lesson for all.