tumble test


February 9, 2005, 02:21 AM
I got to wondering. There's myths out there about various rounds being designed to tumble upon exiting the barrel. There are rounds that are designed to tumble upon striking a target, to cause more damage. I got to thinking about how to test this, and came up with this:

several sheets of paper are set up in a row. In the middle is a trigger, I was thinking a thick peice of foam or a thin sheet of plywood. The purpose of this is to simulate a strike, to produce a tumble. By having the paper in front, you can see if it starts tumbling out the barrel, or if it takes a hit to make it tumble. A round that doesn't tumble would produce a round hole all the way through, while a tumbling round would make oblong holes in some of the paper.

This isn't supposed to be scientific, and I know that this sort of test has been done before. But, this setup could be easily reproduced, and could be a fun way to bust a myth for those that refuse to believe the research that is out there. On TFL, someone mentioned plywood wasn't the best material to start the tumble. Anyone here have a good idea? I don't think the range would appreciate me using a slab of beef.

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February 9, 2005, 06:10 AM
I think that a tumbling round would tear the paper badly, rather than simply make a bullet-shaped hole. You'd need something a bit more sturdy than paper for this to work - perhaps thin cardboard, or something like that? However, the sturdier material might also cause the bullet to yaw or tumble, where paper wouldn't.

February 9, 2005, 09:37 AM
ammoman.com has a set of bullet pics stopped by photography, one shows a .223 FMJ tumbling as it goes through an orange.

I think instead of paper you might try something with a bit more liquid to allow for a yawing motion to develop and commence a tumble?

Seems to me to be way too much advanced math involved to figure how to get a bullet to tumble by design. If bullets tumble out the barrel, I suspect it's more of a lack of engineering rather than on purpose.

Then again it doesn't matter much to me if the target gets a hit with a broadside bullet or a perfect impact, as long as I get it's attention and it gives up.


Mr. Mysterious
February 9, 2005, 10:11 AM
Thanks for the pics...I've seen a lot of them before, but it's nice to see them all in one place!

February 9, 2005, 12:40 PM
How about a watermelon? Kind of messy, though. :)

I wonder how the ratio of length to diameter influences yaw in bullets.

A longer bullet would seem to have a longer lever to act upon its center of mass, and yet more mass away from that center.

Rotational velocity is important, too.

Time to drag out the physics textbook...

Smokey Joe
February 9, 2005, 06:59 PM
The NRA did something like this many years ago. (Can't cite a reference--sorry.) Paper worked fine to show tumbling--a bullet going thru sideways leaves a silhouette of itself; a bullet going through at more or less of an angle leaves a lead smear and a non-round hole. Lead wadcutters work best, but any bullet will do much the same.

Anyhow, the paper will work just fine I predict. You might use the heavy yellowish target paper that official NRA pistol targets are printed on--it shows bullet passage particularly well.

February 9, 2005, 08:35 PM
Thanks for the suggestion for the target paper. Any ideas for making the bullet start to tumble?

55 gr sx
February 9, 2005, 09:21 PM
:evil: I would love to have a pic of my 22 250 hiting watermelon
totaly turns them to juice. way beter then a 44 mag or even a 3006

February 9, 2005, 09:33 PM
If you do a search for the 'box of truth' posts from a week or two ago, you can clearly see the keyhole from a tumbling 55 gr bullet, tumbling through 5/8 inch sheet rock.

February 10, 2005, 12:18 AM
Here's the thread with all the links for the "Box O' Truth"...

Links to the Box O' Truth (http://thehighroad.org/showthread.php?t=123000)

I thought it was a very interesting test. Definitely good reading.

Hope this helps!!! :cool:

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