Hello Gangiro:
I cut a 220A savage SG down to 18 1/4" and put a savage adjustable choke, Similiar to a polychoke, and it shoots OK, does not quite have the range as with the 32" bbl. but it's a lot more fun and the choke does work. I found it in a junk box that I bought from a gunsmith in 1982, It's been on the 220 since about that time. It was a cut-off and I chucked it up and bored it out and put it on the 220. I put a military band on it forward of the forend and cut the stock to 12", a lot of fun and I also made inserts for 45ACP as well,,,,did I say that it is a lot of fun too shoot but the slugs(Mags) are not.
Have fun
safety first
HM