Something to think about

M

MSD Mike

New member
I'll use 45ACP with a 230gr FMJ bullet at 830FPS. I think we can all agree this round wont expand under almost any circumstance.
So, how come when you shoot a dog food can (Soup can, whatever) the exit hole is bigger than the entrance hole? Recovered bullet shows no sign of expansion.

Thank
Mike
 
The speed of the bullet prolly pushes the metal out violently and the "petals" tear a larger hole. I believe the entrance hole will be bigger than 45 caliber for the same reason. I've fired FMJ .223 at near max velocities and the entrance hole is prolly .25 caliber (slightly larger than bullet diameter) and the exit is the same...

At least that's from an old machinist/mechanic's prospective...
 
Look at the direction of the curve of the outside of the can is running. Metal is stronger when curved this direction then it is when running in the opposite direction, as is the inside of the can.
Tearout will occur much easier when the metal is curved as the inside of a can is.
This will happen when shooting anything round and hollow.
 
LE-28 said:
Look at the direction of the curve of the outside of the can is running. Metal is stronger when curved this direction then it is when running in the opposite direction, as is the inside of the can.
Tearout will occur much easier when the metal is curved as the inside of a can is.
This will happen when shooting anything round and hollow.
Click to expand...
BINGO ! We have a winner. LE-28 nailed it .
Most people overlook that simple answer....just the curve of the metal .
Good call LE ,
Gary
 
MSD Mike said:
So, how come when you shoot a dog food can (Soup can, whatever) the exit hole is bigger than the entrance hole? Recovered bullet shows no sign of expansion.
Mike
Click to expand...

This has more to do with the can's curve and the direction of travel of the round I believe.

Think of an egg - more pressure can be applied to the points of the egg than to the sides of an egg.

Along the same lines, it takes more energy to push through the outward bowed curve of a can than than it does from the inside of the can outward due to the curve of the metal. i.e. the curve of the can from the outside in has more structural support due to the curve.

I know I'm not explaining it very well.... but I think that's it.... It's why an arch can hold a load above it pushing down.
 
The bullet is not hitting the off side in the same way it hits the outside. Even a thin steel can will cause any bullet to wobble a bit. Then you get into curves and tears.
"...can infestation!..." Shot a full 48 ounce tomato juice can with a 12 gauge slug, long ago(showing off for my Cadets). It blew the lid up and over the backstop of a CF range. Haven't been bothered by cans of any kind since. Had to show a cinder block who was boss with an M-14 a bit later though. snicker.
 
MANY years ago, when I would tolerate stupidity, there was a metal post sticking up out of a fire pit.
An idiot decided to set a can of creamed corn on the post, with fire raging.
It didn't blow up fast enough so another idiot decided to shoot it with a handgun.

I still have a couple of little scars from the blisters creamed corn left behind...
I had no idea creamed corn could go off like a low yield nuclear detonation! :(

I hate creamed corn to this day....
 
It’s just the bullet entering. It’s not just the bullet exiting. A bunch of soup goes out with the bullet, some being pushed in front of it and lots following in the void it creates. The contents of the can are not pressurized during entrance, but, even with the entrance hole for pressure to escape from, they could be thought of as pressurized on exit. As has been well covered, the convex geometry of the impact surface is stronger against crushing/crumpling than the concave off-side. Interesting test of this last explanation would be to line up multiple cans so they’re touching and see if the entrance “wound” on the secondary can is smaller than the exit off the primary, and so on (extra points for seeing how many soup cans a 45 can penetrate and if consistency and viscosity affect this - does chunky beef slow things down more than Italian wedding? - so creamy soups offer more resistance than clear broth soups? :) )
 
If the can has something in it, hydrostatic pressure has an effect. Even an empty can has air in it, though the effect is usually not noticeable.

Agree that the tearing of the exit hole is due to the angle and material of the can's far wall.

Ever notice that paper targets shot with RN have holes SMALLER than the full bullet diameter?? And that the edges of the hole are torn?

Or that paper targets shot without a backing frequently tear in "non-bullet hole shaped" fashion?

The original purpose for wadcutter and semi wadcutter bullets was to cut a "clean" hole in paper targets to aid the accuracy of scoring.

If my numbers are right, an 830fps bullet with a 1 in 16" twist rate is spinning at a bit over 3100 rpm. BUT its not a drill bit, with a cutting point and a groove for cut material so it pushes more than it "drills". Drill a hole through that can, and you will see a slightly raised "burr" where the drill exits. Punch a hole through and the tearing is more pronounced.
 
JeepHammer said:
MANY years ago, when I would tolerate stupidity, there was a metal post sticking up out of a fire pit.
An idiot decided to set a can of creamed corn on the post, with fire raging.
It didn't blow up fast enough so another idiot decided to shoot it with a handgun.

I still have a couple of little scars from the blisters creamed corn left behind...
I had no idea creamed corn could go off like a low yield nuclear detonation! :(

I hate creamed corn to this day....
Click to expand...
I laughed way too hard at this!
 
Thanks for the info guys. The curve makes perfect sense, I'm sure the bullet picks up a little wobble as well. As far as the hydrostatic part goes, I should have added that the cans are empty for this test. I'll have to try shooting two flat pieces of metal to see what happens.

Mike
 
In addition to the curvature, the can isn't moving when punched in the front.
Punches in the front, tears out through the back since can is now moving.
I'm sure wobble factors in also.

Punch in the front, tear in the back.
There is a reason when I carry (not very often) it's a 1911...
I'm not the best shot with handgun, so I want a hit to count.

If ever attacked by creamed corn, I'm just going to RUN!
 
You must log in or register to reply here.
Back
Top