Reaming 7.62 NATO to 7.62x54R

[s11033]

Hey guys, I have a question for people that know about chamber reaming and neck sizes.

I have a sporterized Enfield No.4 that I want to accurize, and I'm trying to avoid having to load .303 Brit. The action is already set up to run rimmed cartridges. I will have to make some tweaks to the magazine, but the bolt shouldn't require any changes.

I have a 7.62 NATO barrel that will fit into the action, but that won't reliably feed and cycle the rimless rounds, which is why I'm looking to the x54r. I'd like to know if I can ream the barrel to x54r without having to set the chamber back. It looks to me like all dimensions are larger in the x54r up to the case neck, where the NATO is larger. The neck dimension I see for the NATO is .343", whereas it's .336" for the x54r. (Also, keep in mind that x54r dimensions is using a .310" projectile whereas I plan to use a .308".) The neck of the x54r begins 1.657" and ends 2.043" from the breech face. On the NATO, it begins 1.560" and ends 1.863" from the breech face.

I'm very surprised by how much thicker the spec on the NATO case is than the x54r. I'm not going for benchrest accuracy here, since I'll just be using iron sights, or at most a 4x scope. But I want to get good case life, and don't like the idea of having a sloppy chamber. I assume the NATO chamber probably has some clearance built in already. Can you guys please let me know your thoughts on whether I need to set this barrel back or not? I don't know what a normal clearance is in the neck.

Thanks!