Puzzling reply from Green Mountain Barrel Company

[Abert Rim]

I just emailed Green Mountain to confirm land and groove diameters of their .44-77 barrels, and here was the reply:

Good afternoon,
Thanks for contacting GMRB,
The bore and groove dimensions are as follows.

.436-.438/.445-.4465
Do keep in mind our barrels are produced in lots of 100 pieces or more, so if you are looking for an exact measurement of the barrels bore or groove, you will have to slug the barrel.

Kind regards,

Have you .44 shooters found this much variation in the GM barrels? Asking in order to make the right choice on PP bullet mold/swage dies.

[country gent]

If I read that correctly then the bore can be from a low of .436 to a high of .438, or -0000-.002. The groove is .445 ow side to .4465 high side or .0000-.0015. That is a way tolerances are shown on some prints high and low limit anything between is acceptable.

The other thing it could indicate is taper in the bore and grooves from breech end to muzzle but with the remark about slugging I think it is tolerances

[Good Cheer]

From what I've seen so far Green Mountain typically goes by SAAMI tolerances.
I had that info somewhere in this machine... not too long ago.

[Nobade]

I'd just measure your actual barrel and fit everything to it. Even the guys who say "our barrels are exactly XXX" aren't always correct. At least Green Mountain is being honest.

[Don McDowell]

What Nobade said.

[starnbar]

There are very few barrels that are cut rifling anymore due to cost the majority are button rifled and with the exception occasionally the vast majority will give very good performance. Hence there are more chances with a button rifled to have greater tolerances but most shooters will not see the difference.

[Abert Rim]

Well, Green Mountain tells me they have shipped my barrel, so I will have a chance to slug it here before long.