Or... Get better display for the model(s)
Think I will try this first, will see after that if further actions are needed to ensure safety of the finished models.

The metal replacement shouldn't be difficult. Once you cut the old barrel off at the fron of the mantlet, you already have a centered hole to work with. Just start with a comparable sized bit and start reaming it out, slowly increasing bit size (assuming you have a good selection of drill bits).

I would only drill about 2/3 of the mantlet deep, then just cut the new barrel down for the proper length. A couple drops of CA glue, and you're back in business.

HTH

Thats how I would aproached the situation... Most likely with slipping power tools causing more oval hole that anything
I have ordered the metal replacement, will get back when I have more to show!

I agree with Steve, only I would change the order--- shoot the cat then get a metal barrel
DJ

I had a dragon sdkfz 7 with the griffond PE , the cat jumped on the table and sent it crashing to the floor . Bent the living daylights on the metal and broke all the PE off the model . The cat did not run away she sat there and took all my yelling and screaming at her and as if she understood what she did she stayed and even helped look for the little pieces . Luckily I found them all . And to date she has never ever jumped on the table again , well not that I can see .

. That's just too cruel , give the cat a chance to fix the barrel .

Edmund you are lucky to have such a nice cat... While I searched the parts and put them back on the table, this evil cat sat there and fliped them back to the floor with his paw...

No cat treats anymore . We found the cat in the woods , hungry skinny and scared , she does not want to go outside at all . And she has never ever jumped on the table again .