The short answer is NO!! Even if you place a liner (say mylar, or as I use, strips of old projector sheets) inside the shotcup to prevent steel shot from penetrating the pellet slits, there will be major movement in the shot column as it adjusts to the new bore size. It would be all too easy for a pellet to bounce out of the column ahead of the shotcup and scratch the barrel.The movement of steel as it adjusts is also a bouncing motion, which will happen again as it moves through the forcing cone and then the choke. Even if you don't bulge the barrels--which you probably eventually will, the patterns will go to pot. As stated the necessary speed for steel will exacerbate all problems. There is also the consideration that your gun is possibly overchoked for steel. Modified is effectively full when using steel. No shotcup I know of is actually thick enough to cushion at points of constriction, but if it was, it would also be effectively acting as additional choke constriction. Why not load other non-toxic soft shot??? Of course a full length insert solves all problems except the balance of the gun...and price. Good luck! Steve
