Hey folks,
I tried my first attempt at a shim to fit my 45-70 barrel. When I received it, it was a little bit loose on my frame. I found that I could use mini-feeler guages into the hinge space to size up the fit. With the forend off, I was able to just slip the guages in from the top and then close the action. I went with a .003 as it gave me the tightest lockup. .004 would close but the action wouldn't lock no matter how hard I slammed it. .003 took a firm shutting but would lock up nice and tight. I tested this with some firm blows from a rubber mallet and it wouldn't pop open.
Once I had the size pegged, I followed the tips found in the FAQ section on fitting barrels. Now my barrel locks up vault solid. I'm not sure how many rounds of 45-70 it will withstand but I'm looking forward to finding out.
Doc