AR15 home defense ammo

[Warp]

yep. i'll defer to docGKR on terminal ballistics, but i still like to shoot a round i can afford to use when training. i have untold thousands of rounds of m193 fired and know how reliable it is. i can't afford to run SOST or TAP or any of the cool stuff in volume.

however, when i switched to a 10" SBR, i also switched to using 75g OTM. No real idea how effective it would be but i am confident i can get hits with it and quickly.

I can't afford to fire thousands of rounds of quality defensive JHP (Gold Dot, HST, Ranger) in my carry pistols either, but that doesn't mean I carry Winchester White Box FMJ.

Once I have a proven-reliable firearm, using ammunition of a type that is affordable in volume, I decide upon a reasonable amount of the 'good stuff' to test for function, and then use it, trusting in the reliability of my rifle, the quality of the round, and the reports of reliability from everybody else using that round, and assume whatever risk of malfunction there might be in order to gain the increased terminal effectiveness.

*knock on wood* I haven't yet had a single malfunction in any proven-reliable firearm when using a premium/quality defensive round.

 

[Shawn Dodson]

M855 has greater terminal performance variation than M193 - meaning it's terminal performance is less consistent than M193. Between the two, M193 is a better general purpose cartridge than M855.

Against automotive windshield glass M193 performs better than M855. (I realize we're discussing home defense here, but many are unaware of this fact.)

No, that's why they stopped using M193 and M855 for combat, in favor of better performing rounds.

Both of these cartridges were designed to be fired from a 20" barrel. Problems arose with M855 when it was fired from 14.5" M4 barrels, especially against light barrier materials and at distances longer than about 75 yds where velocity drops below 2700 fps.

M855A1 replaced M855. The newer M855A1 produces less wound trauma than M193 because the M855A1 bullet simply breaks into two pieces - the steel tip and the copper slug base - producing a wound similar to M193 when velocity has decreased to about 2500 fps (and it simply fragments into two pieces). The newer M855A1 performs better against light barrier materials (automotive sheetmetal and windshield glass). (I'm unaware of any M855A1 ammo available to the general public.)

For home defense 55gr M193 is a better choice than 62gr M855 (SS109).

 

[gotigers]

taliv

snip

yep. i'll defer to docGKR on terminal ballistics, but i still like to shoot a round i can afford to use when training. i have untold thousands of rounds of m193 fired and know how reliable it is. i can't afford to run SOST or TAP or any of the cool stuff in volume.

however, when i switched to a 10" SBR, i also switched to using 75g OTM. No real idea how effective it would be but i am confident i can get hits with it and quickly.

I agree on both points.

I still train with m193 and other common rounds to save money, but i always put a few rounds down range of my load of choice. This gives me confidence it works as it should.

I have a stamp coming in a few weeks for a 10.5", so that is the main reason i am using the heavy OTMs.

even in 3 gun, i shoot bulk for most and i only use the good stuff, when i am shooting past 100 yards.

I want to run some gel tests when i get my 10.5. I am no scientist, but it will be nice to see how the bullets perform out of a 10.5" at a few feet out and it will be fun. lol.

 

[Bartholomew Roberts]

Another tacked thread relevant to this question:
http://www.thehighroad.org/showthread.php?t=146306

 

[gotigers]

Thanks BR. That's good info. The AE223 performed better than i thought it would in all but bare gel.

I would like the see the same comparison with heavy(70gr plus) OTMs, MK318 SOST and TSX style bullets.

 

[Infidel4life11]

You really should use standard M193 instead of 855. The 855 does not tumble and fragment like other 5.55 rounds due to its construction. Instead it more zips through a fairly cleanly (compared to other offerings). The military even noted this problem with it when compared to M193.

Gotcha

 

[taliv]

I can't afford to fire thousands of rounds of quality defensive JHP (Gold Dot, HST, Ranger) in my carry pistols either, but that doesn't mean I carry Winchester White Box FMJ.

Once I have a proven-reliable firearm, using ammunition of a type that is affordable in volume, I decide upon a reasonable amount of the 'good stuff' to test for function, and then use it, trusting in the reliability of my rifle, the quality of the round, and the reports of reliability from everybody else using that round, and assume whatever risk of malfunction there might be in order to gain the increased terminal effectiveness.

my solution to that was buy 6000 rounds of "blemished" hornady XTP bullets from midway a couple years back, along with several thousand rounds of regular XTP. I paid $6/100 for the blems and about $11/100 for the regular. So i practice with a load that is substantially identical to my carry load.

Downside is this also means i shot 3gun and other matches with full-power self defense rounds instead of a 9mm formulated to barely make power factor. definitely at a disadvantage there.

 

[Warp]

my solution to that was buy 6000 rounds of "blemished" hornady XTP bullets from midway a couple years back, along with several thousand rounds of regular XTP. I paid $6/100 for the blems and about $11/100 for the regular. So i practice with a load that is substantially identical to my carry load.

Downside is this also means i shot 3gun and other matches with full-power self defense rounds instead of a 9mm formulated to barely make power factor. definitely at a disadvantage there.

Doesn't seem like a downside to me at all.

But then I like firearms activities to be more practical and applicable to the real world and less about gamesmanship and competition for the sake of competition, with something that purposely avoids being realistic.

 

[Shawn Dodson]

Originally Posted by allaroundhunter

You really should use standard M193 instead of 855. The 855 does not tumble and fragment like other 5.55 rounds due to its construction. Instead it more zips through a fairly cleanly (compared to other offerings). The military even noted this problem with it when compared to M193.

Not true. M855 is more inconsistent in its terminal performance yaw and fragmentation characteristics than M193. This has to do with "fleet yaw" issues (the ability of individual rifle barrels to stabilize the bullet - some barrels stablize the bullet more than others (less bullet "wobble" in flight)) and "angle-of-attack" issues caused by bullet construction variations in which some bullets are more stable in flight than others (less bullet "wobble" in flight). Terminal performance can vary from rifle to rifle and from bullet to bullet.

M193 wound profile:

M855 wound profile:

 

[gotigers]

Both of those have long cavity necks and are almost leaving the body before the cavity is fully expanded.

That is why the mk262, mk318 other new bullets were developed over the last 10 years.

 

[Shawn Dodson]

Both of those have long cavity necks and are almost leaving the body before the cavity is fully expanded.

It may be an issue with bad guys of small stature who are centerpunched in the chest. But that usually isn't the situation as the body is usually bladed in a fighting stance and the bullet may have to pass through a hand or arm to reach and penetrate the chest.

That is why the mk262, mk318 other new bullets were developed over the last 10 years.

Mk262, loaded with the Sierra 77gr MatchKing open tip bullet, was developed for use with the Mk12 SPR for long range shooting against enemy soldiers in the open. M855 doesn't perform well at long ranges, where it simply yaws (without fragmentation) and produces a mild wound. Mk262 has poor barrier penetration performance.

Mk318, loaded with the 62gr SOST bullet, was ordered by USMC as it was frustrated with the US Army's never ending "green ammo" project, which eventually led to M855A1 (a design the Army apparently stole from Liberty Ammunition Company). Mk318 has superior "barrier blind" performance compared to M855 which was the primary reason USMC chose it.

 

[gotigers]

as the body is usually bladed in a fighting stance

That is why they have the gel test with that much gel, to simulate body thickness. I would hate to base my bullet choice on a bladed bad buy, but he comes at me straight. "Oh sorry, can you blade so my bullet can work properly". I will stick with the better bullet. The newer bullets have longer cavities. They would not be adopted if they didn't work. The newer bullets don't zip through the bad guy leaving a small hole.

Doctor Roberts wrote about how popular the MK262 was with non snipers because of it great up close performance. This is my favorite choice for home defense, because it is non barrier blind. I dont want to kill my kid hiding in the next room. Well, less of a chance anyways. Different bullets for different needs.

The MK318 is a great round. The M855A1 sounds like a disaster.

 

[Shawn Dodson]

"Oh sorry, can you blade so my bullet can work properly".

As depicted in the wound profiles I posted, M193 and M855 typically yaw by the time they penetrate 4-5".

The graphic posted by Warp in his post #40 depicts a worst case scenario for M855, which is why M193 is the better choice between the two.