comparing the .32 acp (7.65) to a brick through a plate glass window

ostermann

According to Major Boothroyd, the .765 (.32 acp) hits "like a brick through a plate glass window." Are there any scientific minds out there who know how many foot-pounds of energy it takes to propel a brick through a plate glass window? Keep in mind they probably didn't use safety glass in storefronts at the time this was written.

Loeffelholz

No scientific mind here...I always thought the simile was more geared to a comparison between the 7.65mm versus the decidedly underpowered .25 round of the erstwhile "damned Beretta." Besides, the "plate glass window" thing is simply a great line of dialogue---more important here, IMO, than any actual physics-based verisimilitude B-)

ostermann

you're right, it is a great line of dialogue! I just see a little humor in the idea that it really doesn't take much force to put a brick through a window! The .765 isn't a very powerful cartridge (123 ftlbs. according to wikipedia) but much better than the .25 (65 ftlbs.) I thought it would be funny if by pure coincidence the amount of energy was about the same.

perdogg

ostermann wrote:

you're right, it is a great line of dialogue! I just see a little humor in the idea that it really doesn't take much force to put a brick through a window! The .765 isn't a very powerful cartridge (123 ftlbs. according to wikipedia) but much better than the .25 (65 ftlbs.) I thought it would be funny if by pure coincidence the amount of energy was about the same.

The weapon that Connery actually had in the scene was a Beretta M1934 which eventhough the 9mm Corto (.380 ACP) was not as good as 9mm Parabelum, was better than the Walther-PPK or the Beretta-418. ( 267J)

perdogg

ostermann wrote:

According to Major Boothroyd, the .765 (.32 acp) hits "like a brick through a plate glass window." Are there any scientific minds out there who know how many foot-pounds of energy it takes to propel a brick through a plate glass window? Keep in mind they probably didn't use safety glass in storefronts at the time this was written.

Brick weighs 2.7 kg and assuming a terminal velocity of 4.87 m/s, a brick going through a glass window would produce only 32-Joules.

thesecretagent

It's only dialogue, and when you go over it too much it starts to make less and less sense. It is meant in terms of comparison to the .25 Berreta. If comparing the 7.65 to a 9mm, the 9mm would be the one with the said delivery, likewise the 9mm compared to say, a .45. So much of ballistics is down to factors other than calibre. A 9mm with a 5 inch barrel is technically more "powerful" than a .357 magnum with a 2.5 inch barrel. A .22 rifle with a 22 inch barrel is comparable to a 9mm pistol in terms of velocity and penetration.
As for the brick : inertia + weight x velocity > surface area of projectile x angle of trajectory = impact/penetration. All you need is the thickness and resistance factor of the plate glass....