Re: Best barrel length for .260
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: deadly0311</div><div class="ubbcode-body">I run a 18" 308 barrel and was getting a average velocity of 2750ish with 155 scenars
My 260 has a 24 inch barrel and with 8 twist and running the 140 AMAXs around 2820 fps. </div></div>
To a certain extent, we are talking apples and oranges with these two bullets. The 308 155 gr scenar has a sectional density of .233 and the 264 140 AMAx has a sectional density of .287.
Each psi of pressure behind the 140 grain AMAX is having to accelerate more grains of bullet than the pressure behind the 155 Scenar. If a .264 bullet of comparable sectional density to the 155 scenar were used, it would weigh about 114 grains. And it would accelerate to a higher velocity than the 140 grain bullet.
The 140 grain 264 would retain more of its starting velocity and energy downrange due to better wind cheting shape.
The 260 Rem has proportionately more powder for the bore than the 308. And the 243 has even more powder proportionately than the 260.
In any case, as previously stated, it is all compromises between overall weight and handiness of the rifle.
In my original post, I was just observing that there are some interesting numbers one can get with the different bores and barrel lengths. Intuitively, it would seem that proportions would be relevant. But there are a bunch of other variables involved. The relative powder is not consistent between the 308, 260, and 243.
In terms of smaller bores needing longer tubes for accelerating, it is true that they have proportionately greater surface area, and therefore more friction against the bore, all else equal in bullet shape. That is why larger bullets have better ballistics. Their surface area doesn't increase linearly with the bore or weight, since the volume (and weight) of the bullet is proportionate to the radius squared. Again, all else equal in terms of bullet shape.
I've wondered what we would find if we got chronograph figures from some number of Remington 308 LTR's with 20 inch barrels and the same number of Remington 308 varmints with 26 inch barrels, same 1x12 twist, same number of lands, with the same lot of Federal 168 grain gold medal match. Or, get ten 26 inch varmint barrels, and cut off two inches at a time, going down to 16 inches.
And that's enough math from me for one night.
Run what floats your boat.
