Right off the top I have no experience with the Remington740. It was made from 1955 to 1960.It was replaced by the model 742 which I did own a couple of over the years. Something I would consider parts for the Remington 742 are getting scarce. The 740' s parts would PROBABLY be next to impossible to locate.I think you would be better off getting a newer rifle that parts are available for.I have a Old Remington 760(pump). Remington discontinued this model. They no longer stock replacement parts for it.If and when I need parts for it I' ll be looking for a parts house that carries Remington' s obsolete models parts..The 6mm is a decent round.I prefer something a little bigger for deer,but that' s just me.With proper shot placement the 6mm is fine.
Ruger Redhawk