Can an hw3 lr modified its chamber to fired a magnum ammo?

Not sure what an HW3 is, but if it is a firearm chambered for .22 Long Rifle, no, it cannot be "rechambered" to .22 Magnum. The .22 magnum fires a larger diameter bullet than the LR, and has higher pressures. The two cartridges do not interchange except in a few revolvers that have 2 cylinders- one LR, one magnum.