What happens when you fire a .45 with a bullet stuck in the barrel?
Surprisingly, not very much! HS Arms tested their .45 HS-45 pistol by firing a under-loaded round that did not exit the barrel then firing a factory round.

“precisely measuring of the pistol parts showed only a small up bulging of the barrel, resulting from the extremely high pressure loads.”.
Bullets getting stuck in barrels is not uncommon when shooting .22 Long and .22 Short rounds in a rifle due to their very low velocity and energy. I did think that in a pistol the pressure would cause more than marginal bulging.
Read the article here.

Some days things don’t work out so well. I had this guy in my 449 class… It was a $1500 Les Baer IIRC.
http://www.thegunzone.com/colt45-40.html
Don’t try this one at home folks!
Hi TD. I did not know that! Thats very interesting. And it makes sense in retrospect, considering the slight damage the 2nd round did!
Counterintuitive as it seems, the .45 ACP is actually a lower-pressure round than the .22 LR!
SAAMI specs allow a max average pressure of 24,000 PSI in the .22 LR vs. 21,000 PSI in the .45 ACP.