Shape of .40s&w bullets

[Young.Gun.612]

Not sure if this is the correct section, mods feel free to move this thread.

I've always been curious as to why .40s&w bullets are shaped like a truncated cone. It seems like almost every other projectile I've seen is completely rounded at the tip. Just something I've always wondered. Anyone know?

 

[checkmyswag]

Good question. Sure some folks here know but not this guy (points at self).

 

[mete]

Makes a shorter round ! When the 40S&W was developed they wanted a round which would fit in the 9mm frame size .The round had to fit into the 9mm magazine also.The best thing they could do was to use a truncated bullet which is better anyway as it has a bit better performance ,more stopping power and less deflection.

 

[KLRANGL]

As mete said, most likely because of max overall length requirments. Compare .40 with 9mm:

 

[carguychris]

As mete said, most likely because of max overall length requirments.

To be a bit more specific, a truncated-cone or flat-nose shape allows a bullet to be more massive and have more bearing surface for the rifling compared to a round-nose projectile of equal length. This allows it to fit into a smaller magazine while retaining adequate muzzle energy and accuracy.

For example, middleweight 9mm component bullets are commonly sold in both shapes. Stand a 124gr RN 9mm bullet next to a 124gr FN bullet and you'll notice that the FN bullet is ~0.15" shorter yet has longer flat areas along the sides.

The tradeoffs are that it's harder to make a FN projectile feed well and its external ballistics are inferior at long range. However, modern pistol and SMG users generally expect flat-nose JHP bullets to feed flawlessly, so gun designers already design firearms around this requirement, and these types of guns are seldom intended for engaging targets beyond ~50yds anyway.