As far as I know you can not tell what kind of rifling you have with the serial#. Best way to tell is to look down the barrel and count the lands and grooves. there should be only six of each. And most likely the ones marked Ilion NY ,will have Ultragon rifling. I did not see any Gardner MA with this rifling, they all have the old rifling with more rifling grooves. The reason I know all this is becausae I have been looking for a 20ga. USH for a few months and could not find one at a gun dealer with Ultragon Rifling. So I sent in my SB2 frame and had a barrel installed , called CS first and made shure the new barrel is Ultragon. They said all new barrels at the factory are Ultragon. Dealers and supliers still have the old ones they are getting rid of first. Unless you are lucky and they just received some new ones. I do not know if it is a better rifling since I do not have any experiance with the old rifling. The Ultragon barrel I received shoots very good, tried different slugs, most aren't too bad but the best seem to be the Remington Acutip . They are holdong a nice 2 1/2 group at 100yrds. 2 1/2'' high at 100yrds. should be right on 0 at 150yrds. (next time at the range I'll give it a try at 150yrds.
