I am courious to know how many different forearm slide tubes were made in the 20 gauge. What length variations are there. I found a nice set of wood an the gentleman said his forearm measured 7 3/16 - 7 1/4 from tube nut an to where the collar sets inside of forearm. I measured mine that I have currently an it's 5 3/4. So my question is if they made longer tube variations for the 20 gauge an if so, can I swap out my forearm tube with a longer one an everything still work.

the majority of my M-12's were made before 1930 and one has a 4 digit serial number that I assume means it was built in 1912 and the forend wood is interchangable between all of them.