Euro 7mm vs NA 7mm

[Cleftwynd]

Have any of you ever heard about this?

"An American 7 mm cartridge has a slightly smaller bore. European 7 mm cartridges all have 7.24 mm (0.285 in) grooves diameter. American 7 mm cartridges have 7.21 mm (0.284 in) grooves."

Is it true? Just because I read it on the internet doesn't mean I will blindly follow. Most likely true but...

If it is, have any of you ever taken that into consideration when selecting bullets for your European made 7x57, 7x64 etc...?



Regards, Bill

 

[p-17]

I've heard it, and it is probably true, but I haven't found it to be an issue with my old Mauser 7x57. It may sound like sacrilege, but I've never noticed a serious accuracy difference in a hunting rifle if a bullet is .001 or even .002 undersized to the bore.

Most old .303s have bores that are actually .313 or .314 because that is what the old British specs circa WWI called for. This hasn't stopped us from using .311 and .312 bullets out of these rifles for 100 years, and some of them are even fairly accurate (the P14s with Hornady bullets come to mind).

My suggestion is to keep shooting standard .284 bullets. If you have an accuracy problem, check your action, bedding, trigger, and scope first. If they all check out, then try using a different brand of bullets or powder. If none of these things work, then slug your bore and see if you can get a bullet that is the exact fit. I would do this last because the other things are generally more significant in accuracy than a slight undersize in the bullet.