I have an LRS-2 (similar but the action is shorter and does not handle .338 Lapua). You can get parts, other barrels, boltheads on gunbroker, and the blaserpro website. It would be interesting to find out if the barrel configuration for the Tac-II is the same as the newer R8 hunting rifles. If so, you can swap in barrels make that gun just about any caliber under the sun. The LRS-2 that I have can swap in/out any barrels from the older R93's.
Hope this helps.
BTW, all of the blaser barrels that I have for the LRS-2 (223, 22-250, 243, 6.5x55, 308 and 300 WM) all shoot 1/4 MOA ... they just hammer.