Bullet Board: Hornady 3.08 180-Grain Interlock.
An all-around hunting bullet designed for use on deer- to elk-size game, the InterLock BTSP features a lead-alloy core in a tapered, boat-tailed jacket. A crimping groove is swedged into the jacket and mechanically locks the core in place. The generous exposed-lead tip initiates immediate, dramatic expansion on impact, and the tapered jacket and InterLock ring control expansion to create a good mushroom shape. It's not as cutting-edge as its newer polymer-tipped cousins, but it's a solid, reliable bullet that's been bringing home the deer for decades.
This bullet was used to take a cow elk. Fired from a .30-06 at an estimated 2,700 fps from a distance of 125 yards, it impacted the elk with a remaining velocity of about 2,500 fps.
Driving directly through the ribcage, destroying both lungs as It went, the InterLock penetrated some 18 inches and lodged against the offside hide. The elk ran about 40 yards and dropped.
As you can see, several fragments were recovered along with the mushroomed bullet. Together, they weigh 102.2 grains; the bullet alone is 87.4 grains, or about 48 percent of original weight. Expansion averaged 0.482 inch, just over 1.5 times original diameter. However, maximum expansion--as the bullet shed large portions of its front--would have been massive, likely three times original diameter.
Because this type of bullet tends to shed quite a lot of weight, I've experienced the best performance with heavy-for-caliber versions. Accuracy tends to be excellent. Handloaded or with good factory ammunition, many rifles will shoot the InterLock into less than 1 MOA.