Lee- Your action has to be an SB2 alloy heat treated one with
larger shotgun firing pin. Best to get whole gun for 250 bucks.
I think you have to send gun in to get another barrel
on it, which is a pain, and it not having big firing pin
they probably would refuse to do it.
Give smith some to go from 3" out to 3.5", or if he
can for long case, which fires 3.5" plastic fine like mine does.
For the long 12ga FH case, after we had a guy put on rims with
CNC, we then annealed cases, and fireformed them. To load plastic loads
you will be near top of shotgun pressures like magnum turkey and goose loads
which expands case bases the max amounts. And they are real hard to size
with regular dies, with the bases getting beat up, rims all bent
in sizing process, and time consuming.So you need a Super
Sizer by MEC, a collet resizer, takes seconds to size case factory perfect,
then case will go through shotgun loader like greased lightning. Also
cases last 3 times longer. I got 300 3.5" cases for about 10-12 cents each,
and few bucks shipping. Our long brass case we figure we have 6 bucks into.
And you can still ream it out to long brass case from the 3.5" if
you do that first. I have hundreds of what were hard to size
3" plastic given to me, that with sizer I can now easily use also.Ed