Originally Posted by azsugarbear
Most barrel erosion occurs in two areas of the barrel: the throat and the muzzle. The throat gets the brunt of the abuse through heat and chemical. The muzzles tends to wear and becomes less round and more "fish eye" in shape. As a general rule, bullets will gain about 25 fps for every inch added. But this is only true for barrels in the 20' to 26" range. After that, it becomes a game of diminishing returns. It can actually become a detriment and slow the bullet down if the barrel is too long. Dan Lilja wrote a pretty interesting article on the subject a while back:
Lilja Precision Rifle Barrels - Articles: Barrel Lenghts and Velocities in the 338/378 Weatherby Magnum
Both the 308 and the 30-06 get great barrel life and throat wear. You begin to see some shortening of barrel life in the 300 Win Mag. The 300 Ultra Mag shows even more. A max load for a 180 gr. bullet in a 308 is approx. 48 gr. of Win 760 @ 2600 fps. A max load for a 180 gr. bullet in a 30-06 is approx. 56.5 gr. of Win 760 @ 2800 fps. Max loads in 300 Win Mag require about 70 gr. of powder, while the 300 RUM requires 90-95 gr. to reach max velocity with a 180 gr. bullet.
My point is this: you need substantial drops in powder to begin to realize any saving in the area of throat erosion. Even the 30-06 burns 18% more powder, but does not suffer from shorter life due to barrel erosion. Most starting loads in reloading manuals for any of the above calibers are only 5% under the listed max loads. To gain any appreciable decrease in barrel wear (such as between the .308 and the 300 Win Mag), you are looking at a decrease in powder of 30% or more. It just isn't practical in light of other factors mentioned previously.
You & Michael have given me a lot of information to think about. Because of an extreme A.D.D. condition, it takes me a bit longer to retain new information. Been this way since childhood.
My new rifle will be chambered for the 22-250 & I know I'm not I'm the same league as the guys shooting big bore way beyond 500 yards.
I want to go to that link you provided & read more. This will help clarify what the two of you have have already told me. I did a number of searches online trying to use different phrases to come up with some leads, with no results. I wasn't even sure I'd get any responses here.
It appears as though even 4 inches increase in barrel length can't compensate for any realistic drop in charge weight. Another case of diminishing returns
Since birth (1941) I've always needed to understand things to a degree beyond what most people accept. I don't just want to know the answer, I want to know why. I've never been able to let go of that way of thinking.
Most people look ay me and think or say, "WTF are you talking about?"
Clarification in my mind doesn't happen fast for me, but I don't let go until it does.
My mind has a pattern of wandering off in tangents, so there's more than a fair chance I'll be back with more questions or thoughts.
Thanks again for the time you two have been willing to take with me.