If you're going to use RST shells, you won't need to extend the chambers. I wouldn't trust a gunsmith to measure anything more complicated than barrel length. Is cutting your wife's credit card so hard?

Just go buy some light load shells, Rem, Win, Fiocci, Fed, RST etc and don't worry about it. We have thread after thread here about chamber pressures being minimal, about actual hull lengths being less than nominal, ad infinitum. Remember, these things were proofed the same as fluid steel.

If a person is leary about damascus, they can bundle themselves up like Ralphie in A Christmas Story, wear a motorcycle helmet, hold the gun at arms length and pull the trigger. Absolutely nothing dire will happen. I know, because that's what I did years back.

Longer shells in short chambers won't raise pressure much. This practice can however add "felt" recoil. Case in point, I shoot 3" shells in a 2 3/4" Parker for ducks with no noticable effect in recoil. Alternatively, I have a Lefever 20 gauge that had 2 1/2" chambers. Boy would it kick with 2 3/4" shells!!! I had those chambers lengthened to 2 3/4". The problem may have been due to the angle of the forcing cones but I have no data on this...

Sherman Bell published his tests of long shells in short chambers in recent years in the Double Gun Journel. The maximum effect in pressure was for one gun/shell combination was to raise it by 1000 psi. Most combinations were much lower than that.

Mark

No one be touch'en my wife's credit card! You want to keep your fingers? One year I gave her a Swiss Army Knife to keep in her purse. Big mistake. Now she goes armed.

Truthfully, she likes to see me messing with my gun collection. She says I look so involved and contented, which is true. That last buy, of the GH, made her eyes perk up however. I told her it was my last. I lied. She knew it. We've been hitched for over 30 years....thirty long, long years.