I understand that the bad rap for erratic pressure the 7 Rem Mag got was due to tight chambers from dull reamers trying to keep up with production demands.
Where did you get that from?
mathman, Mule Deer posted this in another thread, maybe what he thinking:
Bob,
All pressure barrels used by SAAMI members are supposed to have chamber (and bore-groove) dimensions that meet SAAMI standards. In other words, I sincerely doubt the Nosler pressure barrel has an out-of-spec chamber throat.
I do know that for a few years after the 7mm Remington Magnum was introduced, demand for rifles was so high that some factory-rifle chambers varied considerably in dimensions, creating problems with SOME factory ammo.
I suspect the problem with your BAR (and others) might have been due to the factory using worn reamers, to keep up with demand. Unlike custom gunsmiths, factories use relatively inexpensive reamers that start out on the upper edge of SAAMI dimensions. As the reamers wear, they naturally cut smaller chambers. Factories normally quit using reamers when they wear to minimum SAAMI dimensions, but occasionally don't, for whatever reason. The neck dimensions can get pretty tight, especially with some brands of brass with thicker necks.
Brass that's been fired and resized a number of times also tends to develop "the dreaded donut" at the base of the neck, due to the thicker brass in the shoulder moving forward. This can cause pressure problems as well. I first ran into the donut back in 1974, when handloading for my first .243 Winchester, but it occurs in quite a few cartridges, especially when brass gets sized so the shoulder doesn't firmly contact the front of the chamber--common in belted cases.
