Why Is .40S&W a truncated bullet ?
- Thread starter Mike H
- Start date
Good question.
I've given this some thought too.
The only feasible reason I can come up with would be that the .40S&W was targeted for law-enforcement.
Law enforcement would undoubtedly use JHP for duty, so to market an approximate for pratice having the same profile and bullet weight, the truncated profile would work.
Also, the truncated profile cut targets cleaner than conventional FMJ profiles.
That's the only reason I can come up with.
I've given this some thought too.
The only feasible reason I can come up with would be that the .40S&W was targeted for law-enforcement.
Law enforcement would undoubtedly use JHP for duty, so to market an approximate for pratice having the same profile and bullet weight, the truncated profile would work.
Also, the truncated profile cut targets cleaner than conventional FMJ profiles.
That's the only reason I can come up with.
My theory is that originally the .40 was designed to shoot the heavier 180gr bullets. In order to meet OAL restrictions to fit in the 9mm frame size pistols the 180gr bullets were designed with truncated nose, therefore shortening the OAL of the cartridge while still allowing the bullet to weigh 180grains. With a conventional round nose bullet you would have to seat the bullet deeper in the cartridge case, leading to even more pressure problems.
Why this practice was continued for lighter weight bullets I have no idea other than another theory...
I would think most manufacturers of the bullets did this so that they would have as much bearing surface as possible to help stabilize the bullet. Even with the lighter bullet weights the .40 in a round nose fmj may have an extremely small amount of bearing surface in the .40 cal size making the bullet perform much like a ball rather than a spitzer shaped projectile.
Just my guesses...
Good Shooting
RED
Why this practice was continued for lighter weight bullets I have no idea other than another theory...
I would think most manufacturers of the bullets did this so that they would have as much bearing surface as possible to help stabilize the bullet. Even with the lighter bullet weights the .40 in a round nose fmj may have an extremely small amount of bearing surface in the .40 cal size making the bullet perform much like a ball rather than a spitzer shaped projectile.
Just my guesses...
Good Shooting
RED
I've read that Luger designed the 9mm with the truncated nose, but the design was changed cause the 'enemy' could take this design as a 'dum-dum' bullet (doesn't sound very convincing, though). The idea of the truncated 9mm (and maybe the truncated .40) is that in FMJ it performs better against human targets while retaining penetration. If memory serves well, the 10 mm was designed back in 1979, when the US Army still had the 1911, so perhaps the idea was to design a better performing FMJ bullet to be sold to the military as well as civil gun owners. Just my opinion...
Truncated bullets peel their jacket back and expand more easily than round ones, which have a thicker side profile. The first .45ACP hollow points were also truncated, until it was reported that too many people were having feeding problems in their guns. I'd assume that since the .40 is a new round (i.e., no WW1-era .40 weapons to worry about) both it and the guns that chamber it are designed for use with truncated ammo.
Edward429451
Moderator
My thoughts are, since they was looking for middle of the road cartridge when they was designing the .40 S&W (To go between 9mm & 45), that they was trying to stay away from the round nose and its horrible overpenetration problems that the RN gave em in the 9mm. Just a guess really..
Walt Sherrill
New member
Could be, too, that a truncated bullet lets you pack more BULLET into the available space...