There are two thing going on here. The strength of the barrels and that of the action. If you line the barrels or make new ones they WILL NOT blow. Barrel makers test them to 120k PSI. The CZ action is made from 4130 or 4140 heat treated chrome molybdenum alloy steel. In double rifle speak we use tons of pressure. A 450 NE is close to a 45-120 and produces 17 tons max. Dropping the velocity back to 1850 FPS will reduce you pressure to about 10-12 tons and work fine for just about any thing short of a charging elephant. How do I know this? I have a 45-120 built on a 16 gauge CZ shotgun.