I' d say 99% of the factory' s use " pressure" barrels to chronograph, and shoot groups when testing their ammo. They are special barrels designed to measure the pressures from the cartridges. That' s one reason most .270 ammo will show a velocity of 3,019 fps (I think that' s what it shows) when in reality, in real life rifles, shoot anywhere from 2800 - 2950 fps.

Skeeter, that' s kind of odd about the green box. I assume you' re talking about Remington Core-Lokt. My old Browning Abolt .270 shot 3/4" groups with that ammo and Federal Premium. The Remington was quite a bit cheaper.