Full Metal Jacket Boat Tail (FMJ-BT) Bullets Explained
As with any full metal jacket, the full metal jacket boat tail has a bullet either fully or mostly encased in copper or another hard metal or material. The boat tail type is commonly used for competition shooting. The way these are designed is with a tapered rear of the bullet and when viewed from the side, they roughly resemble the way a boat is shaped. These rounds are favorites of reloaders because they tend to be easier to assemble without denting, nicking or scratching the bullet surface. Any tiny imperfection can lead to unwanted bullet performance or even cause issues with the casing.
When the bullet is fully encased it can be called a TMJ or total metal jacket bullet but these are commonly only encased on all sides but the rear. The reason for the casing is two-fold. It can limit the amount of lead spread in the air when firing and can add penetration. Full metal jacket boat tails tend to be fully encased to limit lead issues even more.
The whole purpose of the FMJ-BT was to provide a more stable flight and increased accuracy. This is done by tapering the end of the bullet causing an increase in the ballistic coefficient.
Today, most shooters demand the accuracy of the boat tail design as it out performs the designs of the past. Most precision rifle shooters, like those who shoot F-Class competition, rely on the consistency and long range performance of the boat tail design.
There aren’t a lot of true disadvantages to this bullet type unless you’re using them for something other than their primary use. Depending on the manufacturer this could be competitive shooting, long range practice or even hunting. The one thing a lot of FMJ bullets suffer from is overpenetration. These bullets can hit a target, go straight through and keep on going. This is because unless they were designed to tumble or fragment, they remain pretty much intact on impact. This will depend on the target material of course. Typically you won’t be using these bullets for home defense unless the zombie apocalypse happens to occur.
Some areas don’t allow the use of any FMJ bullets, even boat tails so make sure you know what’s allowed on the range you’re going to, the hunting area or other public land so you don’t get in trouble once you start shooting.