Q: I’m tossing up between having my 7mm-08 rechambered for the .284 Winchester, but have never seen a comparison of how they stack up when compared on an equal basis. With everything, including action length, barrel length and the chamber pressures being equal, how do the 7mm-08 and .284 Win. compare in velocity with a 140gn bullet? But I am most interested in the 7mm-08 versus the .284 in short action rifles.
A: All things being equal the .284 Win. will drive a 140gn bullet at least 100 fps faster than the 7mm-08. This is because the .284 has a larger powder capacity than the smaller 7mm-08. When the .284 Win. is loaded to the maximum overall cartridge length allowed by the short magazine box of a short action rifle, (usually about 2.80″) the bullet must be seated deeply into the powder space. This reduces its combustion chamber somewhat and also reduces the slight ballistic advantage it has over the 7mm-08. Based on my experience with both cartridges in short-action rifles, the .284’s edge is reduced to 75 fps. In other words, any difference between their performance in the field is nothing to worry about. Both are excellent cartridges and you won’t go wrong whichever one you choose, but ammo and cases for the 7mm-08 are readily available whereas .284 brass is hard to come by.