SS109, anything faster than 2600fps (ish) is gonna semi-reliably fragment and leave a big internal torn up hole. I understand that, but what about under that speed?
I heard this comment the other day.
"the steel penetrator moves forward during initial impact so that if fragmentaion does not take place it will loose stability and begin to tumble"
is there any truth to this?

Loads such as M855 using the SS109 bullet or M193, will generally fragment at or above 2700 fps. The higher the velocity the better the results. But keep in mind that these bullets may not be quite as consistent at fragmenting as we once believed. I have seen various knowledgeable people claim that these bullets fail to fragment as much as 20% of the time or more. This seems especially true of SS109 bullets because there is so much inconsistency in their design. For the most damaging and reliable fragmenters, one may need to look to the heavier match bullets such as the Hornady 75 gr which is an excellent performer and can fragment down to velocities as low as 2100 fps or less. But for general purpose ammo, the M193 and M855 may remain the best options since it is cheap enough to buy in large quantities. But the match loads can be acquired in small amounts and used as specialty ammo, i.e. home defense.

-Charging Handle

There's another important thing to keep in mind about all this tumbling: A conical bullet moves point-forward since it is stabilized by the spin of the bullet in the thin air. The natural tendency is for an object to move with the center of mass forward. Take a straw, stick it in an orange  and try to throw it straw forward. The thing will immediately turn and travel orange forward. Duh so far.

But how many times did the contraption turn ? Exactly 180 degrees ONCE. It doesn't keep flipping ass over teakettle ad nauseam.

The same thing happens when a conical bullet strikes a denser medium. The spin is not sufficient to stabilize the bullet, and it will turn 180 degrees ONCE to travel base first. Ta-da, it tumbled. But that's IT.

So for the bried period of time the bullet is traveling sideways, it creates a larger wound channel. If the bullet is weak enough to be torn apart by the increased forces acting on it, you have the fragmentation effect. If it doesn't fragment due to the bullet's construction, or if the speed is too low, it will simply flip once and that's it.

Make sense ?

What he said ^^

I shot a pile of wood chips many times that was left over from taking down some trees and I was shocked to find the projectiles in whole condition and slightly flattened out on one side only as if it only tumble 90 degrees.

I expected to find pieces if anything at all.

If you have a pile of wood chips, give it a shot. This goes to prove that

A good reason to double tap.  Just to make sure.

yeah I got that from the FAQ, it makes sense. what threw me was the question about the penetrator sliding forward and keeping the bullet moving cone first like a wobbling football toss, then bouncing off bones and what not.

I've been trying to fight the misunderstanding of "tumbling" for months but nobody is willing to read the FAQ so F*ck 'em. But this one guy actually talked with me and came up with this scenario (the movement of the penetrator to cause a tumble) I argued against it but thought I should check in case he as right.


so you're all backing me up then?