Thought I'd throw up a quick post about this. This is far from scientific, and I don't have a great set of data to go with this, but I have a block of Clear Ballistics gel so here you go.
Since I built my first AR and bought gel, I've tested XM193, XM855, and Black Hills 77gr OTM SMK (MK262 Mod1) in search of an ideal defensive load for domestic, civilian purposes (some of the considerations are different than overseas).
All three tests were out of my Daniel Defense 16" CHF 1:7 barrel at 10 yards.
XM193
This was doing about 3225 at the muzzle, based on my chrono results, which means it impacted at about 3195fps. (~1250lb.ft. energy)
Basic analysis of this is that it's nice that it splits into two pieces (the 'wound' track you can't see as well did the same thing), but if you could see some better angles of the spot where it yawed and fragmented, you'd see it shed a lot of lead pieces that didn't really continue and do damage of their own. Where the bullet fragmented, two lighter pieces continued on and the rest of the mass just stayed in place. Significant yawing started around 5.5" and fragmentation looks to have happened at 7.5". Based on the track and other tests I've seen, the two pieces would have come to rest around 17" in these tests, if I had a backer block behind this one.
Pros: Two damage tracks. Good cavity where the round fragmented. Everything stayed within the 12-18" FBI spec for penetration.
Cons: Lost about half the already-light mass at the fragmentation point.
XM855
This was doing about 3025 at the muzzle which means about 3000fps at impact. (~1240lb.ft. energy)
I don't have a good picture of this, but it's easy to describe (I have video panning around the block to look back at). It's a lot like the XM193 shot, but yawing begins at 6.5" and fragmentation happens at 8.5". The difference here is that the damage area around the fragmentation point is less violent looking and only one large fragment continues on (it exited the 16" block with significant energy left and based on what I've seen it would have exceeded 20"). On the bright side of the penetration, three medium sized pieces of bullet fragmented off and made shorter wound tracks of their own (measuring about 2, 3, and 4" respectively).
My feeling here is that you would get more overall damage and bleeding in the fragmentation area (~8.5-14") with XM855, but with XM193 you get two large pieces that are going to be able to hit vital organs. How you evaluate this depends on if you put more weight on heavy bleeding or organ disruption to stop a threat. I personally want to put holes in organs because that stops a threat faster than bleeding out.
Of course the bright side to XM855 is better barrier penetration, if you feel that's a consideration.
Pros: More forward progress by the smaller fragments. Arguably more overall damage in the fragmentation area. Enhanced barrier penetration with the steel penetrator.
Cons: Only one large piece and a small fragment getting to reliable organ depth. Definite over-penetration (risk of collateral damage).
MK262 Mod1
This was doing about 2760 at the muzzle which means about 2735fps at impact. (~1275lb.ft. energy)
Yawing with this load starts earlier at about 3" and fragmentation also starts early at about 4". I would otherwise think this is premature delivery of energy, if it weren't for what the fragments do. This bullet basically explodes, where the other two just break up. From about 4-9" this bullet is throwing pieces off the bullet base, and as these pieces come off they're continuing for 2-4" themselves, and generally continuing at an angle away from the main damage track.
What you get with the MK262 is a messy, violent damage track running from about 4-11", before the core settles down and continues to its resting point. The fragments also extend up to 4" away from the centerline of the bullet's path. Basically this round will create a great deal of bleeding and trauma through the fragmentation area, with both shots in the block producing about 10 significant sub-tracks.
Another good thing is that you get a roughly 40gr chunk that continues well into the FBI's 12-18" butterzone. Basically this performs something like the XM855 but the base stops where it should and much more damage is done in the shallower area. This means you get enough penetration to hit vital organs, not so much that you hit someone behind the threat, and you get a great deal of tissue damage and shredding which will lead to bleeding. If there's a drawback compared to the others, it's that XM193 sends two large pieces to vital organ depth, where this only sends one.
Pros: Very violent wound track. Lots of traveling fragments. Good core penetration without over-penetration.
Cons: None when considered on its own, but compared to XM193 it only has one major chunk traveling beyond 12".
My opinion is the MK262 is the best for defensive purposes against soft threats. It does a ton of damage, is extremely accurate at distance, and has the least chance of over-penetration. This combination makes it ideal for home defense and also ideal at long distance.
The XM855 seems worst to me. I think the penetration factor is nearly irrelevant in this day and age. If the person is wearing Level III armor, the XM855 isn't getting through and nor is any other 5.56. If they're wearing Level IIIa armor the XM855 will get through but so will the other two, because that armor isn't made to stop rifles. The only penetration advantage would be through things like cars and auto glass but... shoot more... you'll get through.
The XM193 would be my second choice. The damage track is nothing to write home about but I like that there are two deep penetrating fragments. The biggest worry here is just how deep they go. The FBI's range is 12-18". The thing is most people aren't that thick and the 18" end of that is more to account for if the round had to go through an arm and bone before getting to the organs. A straight on center mass shot might over-penetrate if it did 17-18" in gel, where as 12-15" would be better suited for a center mass hit with no major obstructions. I'd rather it have a chance of under-penetrating by a bit if it hits wrong, because you can shoot a second time if necessary. That's preferable to a fragment continuing into the next bedroom at 750fps.
Since I built my first AR and bought gel, I've tested XM193, XM855, and Black Hills 77gr OTM SMK (MK262 Mod1) in search of an ideal defensive load for domestic, civilian purposes (some of the considerations are different than overseas).
All three tests were out of my Daniel Defense 16" CHF 1:7 barrel at 10 yards.
XM193
This was doing about 3225 at the muzzle, based on my chrono results, which means it impacted at about 3195fps. (~1250lb.ft. energy)
Basic analysis of this is that it's nice that it splits into two pieces (the 'wound' track you can't see as well did the same thing), but if you could see some better angles of the spot where it yawed and fragmented, you'd see it shed a lot of lead pieces that didn't really continue and do damage of their own. Where the bullet fragmented, two lighter pieces continued on and the rest of the mass just stayed in place. Significant yawing started around 5.5" and fragmentation looks to have happened at 7.5". Based on the track and other tests I've seen, the two pieces would have come to rest around 17" in these tests, if I had a backer block behind this one.
Pros: Two damage tracks. Good cavity where the round fragmented. Everything stayed within the 12-18" FBI spec for penetration.
Cons: Lost about half the already-light mass at the fragmentation point.
XM855
This was doing about 3025 at the muzzle which means about 3000fps at impact. (~1240lb.ft. energy)
I don't have a good picture of this, but it's easy to describe (I have video panning around the block to look back at). It's a lot like the XM193 shot, but yawing begins at 6.5" and fragmentation happens at 8.5". The difference here is that the damage area around the fragmentation point is less violent looking and only one large fragment continues on (it exited the 16" block with significant energy left and based on what I've seen it would have exceeded 20"). On the bright side of the penetration, three medium sized pieces of bullet fragmented off and made shorter wound tracks of their own (measuring about 2, 3, and 4" respectively).
My feeling here is that you would get more overall damage and bleeding in the fragmentation area (~8.5-14") with XM855, but with XM193 you get two large pieces that are going to be able to hit vital organs. How you evaluate this depends on if you put more weight on heavy bleeding or organ disruption to stop a threat. I personally want to put holes in organs because that stops a threat faster than bleeding out.
Of course the bright side to XM855 is better barrier penetration, if you feel that's a consideration.
Pros: More forward progress by the smaller fragments. Arguably more overall damage in the fragmentation area. Enhanced barrier penetration with the steel penetrator.
Cons: Only one large piece and a small fragment getting to reliable organ depth. Definite over-penetration (risk of collateral damage).
MK262 Mod1
This was doing about 2760 at the muzzle which means about 2735fps at impact. (~1275lb.ft. energy)
Yawing with this load starts earlier at about 3" and fragmentation also starts early at about 4". I would otherwise think this is premature delivery of energy, if it weren't for what the fragments do. This bullet basically explodes, where the other two just break up. From about 4-9" this bullet is throwing pieces off the bullet base, and as these pieces come off they're continuing for 2-4" themselves, and generally continuing at an angle away from the main damage track.
What you get with the MK262 is a messy, violent damage track running from about 4-11", before the core settles down and continues to its resting point. The fragments also extend up to 4" away from the centerline of the bullet's path. Basically this round will create a great deal of bleeding and trauma through the fragmentation area, with both shots in the block producing about 10 significant sub-tracks.
Another good thing is that you get a roughly 40gr chunk that continues well into the FBI's 12-18" butterzone. Basically this performs something like the XM855 but the base stops where it should and much more damage is done in the shallower area. This means you get enough penetration to hit vital organs, not so much that you hit someone behind the threat, and you get a great deal of tissue damage and shredding which will lead to bleeding. If there's a drawback compared to the others, it's that XM193 sends two large pieces to vital organ depth, where this only sends one.
Pros: Very violent wound track. Lots of traveling fragments. Good core penetration without over-penetration.
Cons: None when considered on its own, but compared to XM193 it only has one major chunk traveling beyond 12".
My opinion is the MK262 is the best for defensive purposes against soft threats. It does a ton of damage, is extremely accurate at distance, and has the least chance of over-penetration. This combination makes it ideal for home defense and also ideal at long distance.
The XM855 seems worst to me. I think the penetration factor is nearly irrelevant in this day and age. If the person is wearing Level III armor, the XM855 isn't getting through and nor is any other 5.56. If they're wearing Level IIIa armor the XM855 will get through but so will the other two, because that armor isn't made to stop rifles. The only penetration advantage would be through things like cars and auto glass but... shoot more... you'll get through.
The XM193 would be my second choice. The damage track is nothing to write home about but I like that there are two deep penetrating fragments. The biggest worry here is just how deep they go. The FBI's range is 12-18". The thing is most people aren't that thick and the 18" end of that is more to account for if the round had to go through an arm and bone before getting to the organs. A straight on center mass shot might over-penetrate if it did 17-18" in gel, where as 12-15" would be better suited for a center mass hit with no major obstructions. I'd rather it have a chance of under-penetrating by a bit if it hits wrong, because you can shoot a second time if necessary. That's preferable to a fragment continuing into the next bedroom at 750fps.
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