I've got a pint of mercury I accumulated over the years doing electrical work in industrial factories. Many limit switches used mercury and when one failed you had to remove the mercury switches before you tossed them in the scrap. I kept pouring it in a bottle and once I didn't run into those switches anymore I brought the bottle home. I used to clean the muzzle brake ports on my Hi Standard target pistol by hanging a wire on the brake and drop it in the bottle for a night.

marlinguy wrote on Feb 11^th, 2026 at 4:52pm:


That's funny I used my small mercury stash for the same thing cleaning out the lead deposits in my old 102 and 103 Hi Standard muzzle brakes on my Bullseye pistols

Rick

Johnnys Hepburn

You may want to consider electrolysis to clean the bore. I have done this twice, on barrels with hopeless looking bores (heavy scale/leading no obvious rifling under the mess- real sewer pipes). In each case, once the mess was gone I had a real decent clean bore with good rifling just minimal fine pitting remaining where the rust had been. Both good shooters!

Have you done a chamber cast ?   

I agree with Val,  most of mine with S.T.   are set triggers,  maybe that doesn't mean what we think....

What is loaded neck diameter, case wall thickness?
Over .420” may be a problem if the chamber is tight.

A couple things that might be easier than a chamber cast.
Breech seat a bullet to get a fire formed case to measure. 
Flare the case mouth so it drags on the chamber and measure that.
Take a sharpie and color the case and bullet so you can see where it’s hitting.

Remember that they made cartridge seaters for a reason. But remember that forcing a bullet down the bore is different than forcing and oversized cartridge into the chamber.

I’d measure the case neck then pull the bullet, remeasure and make sure the case still chambers. If it does then reseat the bullet upside down and flush with the case mouth, remeasure the neck and again try and chamber the round. That will sort out of it’s the neck hanging up, the bullet in the bore, and a real good idea of max neck diameter.