If I guy doesn't mind laying out the cash, from what I remember the barrel lug that secures itself to the magazine cap is soldered onto the barrel.The othe problemwith an extended 37 mag tube is that you would have to have a very customised barrel for it to connect. Ron Sharpe is your only hope I would think. Good luck.
You still need to hold down the trigger as you pump.
This I understand. The issue is that I (seem to) need to use the "slide-release" after each pump....
Is this even after you have dry fired it? Most 12 gauges are locked after you rack it forward, only unlocking after you pull the trigger or depress the slide release.
Than yours may not be capable of slam firing, I believe they stopped making them like that in the '70s. It could be converted to slam fire if you had the parts.
1942! I'd forget about the long magazine then. The older ones used a different thread style and apparently barrels had to be fitted to the gun by a gunsmith. Suppose you could have a gunsmith fit a new lug in the proper location for you, probably be the easiest thing to do.
But, it is possible?
You have to pull the trigger each time? Doesn't sound like slam fire to me. Like cantom exlplained, holding down the trigger while working the slide should release the trigger, thus firing the action. You shouldn't have to pull the trigger each time, simply hold the trigger down while you work the action.
Glad you sorted it all out. Yes, trigger needs to be held down as you pump.