GNR barrels can be rechambered from your used Contender barrels:


6mm TCU.., 240 Raptor
256 Winchester...256 GNR, 257 Raptor, 256 Falcon, 257 GNR
6.5 TCU...6.5 Raptor
7 TCU...7 GNR, 280 GNR
7X30...7 GNR, 280 GNR
270 Ren...277 GNR
32-20...300 GNR, 30 GNR, 310 GNR
30-30...30 GNR, 310 GNR
30 Herrett...30 GNR, 310 GNR
10mm...401 GNR
41 Magnum...41 GNR, 41 GNR#2
35 Remington...350 GNR

357 Maximum....350 GNR, 358 GNR
 
357 Herrett...350 GNR

357 Magnum...356 GNR, 358 GNR, 350 GNR
375 Winchester...375 GNR#2, 378 GNR
45-70...450 GNR

Encore barrels
44 Magnum...429 GNR, 440 GNR
444 Marlin...440 GNR
454 Casull...455 GNR

45-70...450 GNR