I had a M1950 carbine in caliber .270 Winchester rebored to 9.3X62 and the magazine altered with no problems. As mentioned above, with a smaller bullet and case neck, the 6.5X65 RWS should feed with no further alterations. I hope your M1950 is a rifle, however. I would think a carbine in 6.5X65 would be truly a pain in the ear to shoot.