Which would you choose given the parameters.....

[vicious_cb]

No doubt they can be devastating with a perfect shot, but we could also make the case for humans being more like dangerous game: shooting back, actively trying not to present a perfect shot, and wearing thick "skin" of various forms. I share Todd.K's expressed opinion on this. I have my doubts that the intact base of a 62 grain bullet (after passing through a limb or obstruction) is optimal, even if it penetrates, else one could carry 5.7 ball and save a lot of weight. I therefore believe that the design of the M855A1 bullet and to a lesser extent 77 grain SMK/TMK come with some trade-off, compared to bonded bullets in pure flesh-and-bone performance from suboptimal angles.

You are describing exactly what the 12" FBI minimum was based around, it doesnt matter what the original weight of the bullet was or how much weight is shed from fragmentation as long as the core of the bullet is sufficiently penetrating into the vitals. Just looking at human anatomy you only need to penetrate a few inches with a frontal upper thoracic shot, then pretty much any round could do this. 40gr V-max, probably even 36gr varmint grenade would do the job. That 12" ensures the core reaches the center of the chest cavity from ANY angle, even after passing through the entire upper arm. The fact is, with modern technology you can design a bullet however you want, you want a penetrating core to punch through 18" of gel after fragmenting, they can built that too. You are only limited by how much the energy the projectile has to work with.

There are a few non-bonded lighter loads that Doc recommends:

If barrier penetration is NOT an important factor AND your rifle can't stabilize the heavy 70+ grain bullets:

Sierra 69gr SMK loads
Hornady 68gr OTM loads
Winchester 64gr JSP (RA223R2)
Federal 64gr TRU (223L)
Hornady 60gr JSP

[okie]

OTM fragment from yawing not because the open tip expands like a hole point.

Hmmm...I honestly don't know for sure. What I've read is that the open tip opens up in similar fashion to a hollow point, or at least can, and that's what causes it to shed its jacket and fragment at low speeds. It is for all intents and purposes just an FMJ with its jacket on backwards, so you wouldn't expect it to behave too much differently from an FMJ unless the open tip is indeed doing something along those lines. I've read that it will fragment at speeds where FMJ almost certainly wouldn't, and is virtually immune to fleet effect at all ranges, so on that account...I would have to conclude it has some HP like properties.

Either that or the rumors of its reliability in those regards are greatly exaggerated. Hunters do complain about it ruining a lot of the meat in the shoulder, though, which kind of substantiates those rumors a little bit, as you wouldn't expect a 77gr FMJ to ruin a bunch of meat at 2500fps.

[ABNAK]

No doubt they can be devastating with a perfect shot, but we could also make the case for humans being more like dangerous game: shooting back, actively trying not to present a perfect shot, and wearing thick "skin" of various forms. I share Todd.K's expressed opinion on this. I have my doubts that the intact base of a 62 grain bullet (after passing through a limb or obstruction) is optimal, even if it penetrates, else one could carry 5.7 ball and save a lot of weight. I therefore believe that the design of the M855A1 bullet and to a lesser extent 77 grain SMK/TMK come with some trade-off, compared to bonded bullets in pure flesh-and-bone performance from suboptimal angles.

As I'm sure you know there is no free lunch in life, terminal ballistics included. One must make a choice for what works best for the majority of their possible scenarios, which is why I asked that in the OP. Essentially bonded (the FBI load) vs. fragment-and-penetrate (Mk318 or M855A1) vs. Mk262. The feedback here has been excellent, like I knew it would be, especially from the BTDT folks. That is why I love this site!

[Disciple]

You are describing exactly what the 12" FBI minimum was based around, it doesnt matter what the original weight of the bullet was or how much weight is shed from fragmentation as long as the core of the bullet is sufficiently penetrating into the vitals.

I am aware of the standard. Merely penetrating 12" of bare gel with some unspecified fraction is not sufficient for me. Even .22 LR can do that. Bones do in fact matter, and an ice-pick is not the equal of a well formed mushroom. Barrier penetration IS an important factor in my choice whether that barrier is auto glass or a pelvis.

That 12" ensures the core reaches the center of the chest cavity from ANY angle, even after passing through the entire upper arm.

[vicious_cb]

I am aware of the standard. Merely penetrating 12" of bare gel with some unspecified fraction is not sufficient for me. Even .22 LR can do that. Bones do in fact matter, and an ice-pick is not the equal of a well formed mushroom. Barrier penetration IS an important factor in my choice whether that barrier is auto glass or a pelvis.

Its a valid concern, you don't need to pick a bullet that barely makes it to the 12" mark with a small chunk of bullet. The ideal range is 12-18" there are plenty of rounds that going well past that, M855A1 and Mk318 cores are going well past the 18" but if you want significant fragmentation AND expansion, well that where the limitation of 5.56 energy comes into play. The projectile just isnt carrying enough energy to do both, so its up to you to choose what you prefer. Even I run 2 different rounds. 75gr GDSP for general purpose,works great around vehicles, deep penetration and 77gr TMK for long range SPR stuff or if I still lived in an apartment, as a limited penetration home defense load.

Even a round like 77gr TMK that has explosive fragmentation is still punching bone with ease.



Despite gel penetration of only 12.5", this bullet is still punching both sides of rib cage on this Razorback boar at 50yds and still exiting. And humans are more delicately built than a thick hide, thick boned razorback.

[Disciple]

That 77 TMK is class leading by almost all accounts. If I were a better shot I would have to get some. What is the real-world retained weight with those when they do not pass through? It looks to me like the majority of the mass made it past the 12" mark in that gel shot.

[1168]

Hmmm...I honestly don't know for sure. What I've read is that the open tip opens up in similar fashion to a hollow point, or at least can, and that's what causes it to shed its jacket and fragment at low speeds. It is for all intents and purposes just an FMJ with its jacket on backwards, so you wouldn't expect it to behave too much differently from an FMJ unless the open tip is indeed doing something along those lines. I've read that it will fragment at speeds where FMJ almost certainly wouldn't, and is virtually immune to fleet effect at all ranges, so on that account...I would have to conclude it has some HP like properties.

Either that or the rumors of its reliability in those regards are greatly exaggerated. Hunters do complain about it ruining a lot of the meat in the shoulder, though, which kind of substantiates those rumors a little bit, as you wouldn't expect a 77gr FMJ to ruin a bunch of meat at 2500fps.

You heard incorrect. For the SMK in 262, its a long bullet that destabilizes/upsets rapidly in flesh and the jacket is not thick enough to hold together under the increased forces that occur as the bullet yaws. Something something CG, something something Center of Drag. I seem to remember something about the cannelure coming into play, also. Food for thought on how much force a jacket must withstand during yaw…. Take a look at a 7n6 round that has been fired into gel. It flattens out, but the steel jacket holds together and it extrudes a bit of its core out of its ass. Now add 50% more mass inside that jacket and make it weaker. The hardness or softness of the lead core is a factor, too.

This is of course what makes most fragmenting FMJs work, also. But the design of the 77 SMK makes it happen more reliably. The hollowpoint is irrelevant terminally.

[okie]

You heard incorrect. For the SMK in 262, its a long bullet that destabilizes/upsets rapidly in flesh and the jacket is not thick enough to hold together under the increased forces that occur as the bullet yaws. Something something CG, something something Center of Drag. I seem to remember something about the cannelure coming into play, also. Food for thought on how much force a jacket must withstand during yaw…. Take a look at a 7n6 round that has been fired into gel. It flattens out, but the steel jacket holds together and it extrudes a bit of its core out of its ass. Now add 50% more mass inside that jacket and make it weaker. The hardness or softness of the lead core is a factor, too.

This is of course what makes most fragmenting FMJs work, also. But the design of the 77 SMK makes it happen more reliably. The hollowpoint is irrelevant terminally.

Interesting. So it's basically nothing more than an FMJ and owes its reputation for terminal performance to being a hair bit longer than other FMJs we've come to know, namely M193?

[C-grunt]

Interesting. So it's basically nothing more than an FMJ and owes its reputation for terminal performance to being a hair bit longer than other FMJs we've come to know, namely M193?

Basically. But nearly 50 percent more weight so there is more of the bullet when it does fragment. Also the longer bullet and thinner jacket causes it to fragment at much lower velocity than M193 or M855. Something like 2000 FPS.

Though I wouldnt really call it slightly longer. It's pretty significant. Here is a still shot of 55, 62, 69, and 77 grain bullets. Its from the video which I havent watched, just got the pics of the different bullets from it. A federal 55 grain FMJ has a listed length of .745 inches and a 77 grain SMK has a listed length of .994 inches.

55 v 62 v 69 v 77 by chase, on Flickr

https://www.youtube.com/watch?v=P9PhjX9hoa4

[okie]

Basically. But nearly 50 percent more weight so there is more of the bullet when it does fragment. Also the longer bullet and thinner jacket causes it to fragment at much lower velocity than M193 or M855. Something like 2000 FPS.

Though I wouldnt really call it slightly longer. It's pretty significant. Here is a still shot of 55, 62, 69, and 77 grain bullets. Its from the video which I havent watched, just got the pics of the different bullets from it. A federal 55 grain FMJ has a listed length of .745 inches and a 77 grain SMK has a listed length of .994 inches.

So what about the TMKs that people are making so much noise about regarding their "explosive performance" due to the plastic tip? Pretty much the same story on those, as well?