This is a great point, but how do manufacturers measure velocity for the box/specs? Does it really matter that much? With a 308 rifle it should lose an average of 25fps per inch of barrel lost from 26” to 16.5”. What barrel length do manufacturers calculate velocity for?
I just spoke with Federal (they emailed me back within 30 minutes, I am impressed). They stated that they use a 24" barrel for calculating velocity with 308win ammo.