The little 0 frame PH 16 with 26" twist barrels has a wall thickness at muzzles of: 0.030" right barrel, 0.037" left barrel-- at breech area 0.143" right barrel, 0.143 left barrel-- I have thought about a wall thickness gauge as an addition to my gunroom/toolroom items- I have seen barrel men use them at various side-by events, what is the best make and model and place to buy one- new or used?? Thanks