In the previous post we took a look at Dr. Martin Fackler's effects of terminal velocity on a 5.56 caliber bullet. Velocity causes bullets to break up on impact, and this is largely because lead lacks the tensile strength to hold together with that much force acting upon it.
Previously we covered how a hollow point pistol bullet works, using a hydraulic effect to open up the bullet. When velocities are at the opposite end of the spectrum, the problem becomes keeping them together until they penetrate enough.
How much penetration is enough? Depends on what you are shooting.
|Bear Claw Bullets, from American Hunter|
Evidently there were people who worried about weight loss though, and here is one of the answers. First up is the Winchester Fail Safe. Lead is used in this projectile as ballast, to make the projectile more massive (in the physics sense) and therefore have better penetration. Note the expansion of the lead base into a "fan" shape after use, that hydraulic effect that caused pistol hollowpoints to open up is at work again here, but from the other end. At the level of force acting on the bullet you can think of the lead as a "semi liquid" that is sloshing forward to put lateral pressure on the gilding metal jacket. As you can see the thickest part of the gilding metal underneath the hollowpoint and ballistic tip did not expand much at all relative to the nose or base.
|Winchester Fail Safe|
|Fail Safe After|
Other than solid gilding metal bullets like the Barnes X bullet this is pretty much "state of the art" when it comes to lethality for hunting big game. For hunting varmits older bullet technologies are preferred because they are cheaper and deliver the results expected.
Shifting gears a bit, and shifting the intended target of the bullets, we'll go to war. Specifically war against the Nazis. The US Military maintained the use of the 30-06, and despite having a very good long range round in the M1 Ball loading, adopted the M2 loading because it had less recoil, and at the short ranges where the National Guard could train there was no ballistic difference between M1 and M2 ball loads.
|Sectioned 30-06 AP. Photograph by Carteach0|
If you haven't read Carteach0's investigation into 30-06 Armor Piercing ammunition, now is a good time to do so. http://carteach0.blogspot.com/2012/01/30-06-m2-armor-piercing-bullets.html
A generation later by blood, or two generations by small arms development, the armor piercing properties of the 5.56x45 cartridge were noted, and a Belgian designed bullet, the SS109, was adopted as NATO standard to increase the penetration of service bullets against Soviet mild steel helmets.
What should be noted, is that the steel moved forward in the bullet compared to the 30-06.
|Israeli, Bosnian, Lake City, unknown Photograph by Wolfganggross AR15.com|
Now with the current war on terror, the underfed religious fanatics don't particularly have a whole lot of meat on their bones to stop a bullet hiding behind things like cars, windows, doors and such, and so the military went around trying to fix a marksmanship problem with a bullet solution. The Navy and USMC came up with Mk 318 SOST.
If you think the Mk318 SOST looks an awful lot like the Trophy Bonded Bear Claw, give yourself a pat on the back. Reports from the field have been positive, although I would take that with a grain of salt for now.
|Prototype left, final M855A1 right. Photo by Wolfganggross|
There were a number of different tail configuration, bismuth/tin allow shown as a prototype. I heard about a nylon heavy metal composite being tried as well. In the end, the bullet that flew the best was the solid gilding metal base
Notice that the steel penetrator is fully out front. So you can see the evolution from "steel insert behind lead" to "steel insert in front of lead" to "steel insert without lead" over multiple generations of small arms testing.
So far we have looked at bullets that have been designed to stay together through thick hide and muscle, shoot through Soviet helmets, and finally through car doors and windshields.
There have been other attempts to make "armor piercing" bullets. Initially an extra thick jacket on a 53gr FMJ was used in 5.56x45. Later a tungsten core was used in M993. I mention these because you might find some around, but neither ever saw the widespread usage that 30-06 AP, M855, or M855A1 has in peace and war.