I know the 50's gather more light than the 42's but there could be some mounting issue's if I want a 50 on my muzzle loader,I would rather have a 50mm on the muzzle loader or the 12ga. but if the 50 will not work corectlly I don't want to purchase a 50mm. its shot gun only or muzzle loader where I'm at,and I don't own a rifle to put a 50mm on and I don't want to purchase something I can't use