OK, we all know the concept behind the steel penetrator tip, but in reality, what's the practical advantage?  Standard .556 ammo penetrates car doors and stuff just fine.  And from what I understand, the penetration advantage of the ss109 is only apparent at longer ranges.  Does it have any significant performance advantages against soft tissue?  I'm basically trying to justify the added expense as I only use my M4 for plinking and possibly duty use.  Thanks.
BTW, I'm giving the Santa Barbara ss109 some serious thought.  Can't really find any negative comments on them.  

[url=http://www.ammo-oracle.com/#m193orm855]Q. So which ammo is better, M193 or M855?  And what is all this discussion about fragmentation?  Are these dumdum bullets?[/url]

I didn't have any fancy measuring equipment, but I can tell you that ss109 handily penetrates steel plate that regular .223 or 7.62x39 cannot.  We spent a day with different grades and thicknesses of steel, and the ss109 [u]easily[/u] pierced steel plate from different distances that the rest could not.  For me, seeing was believing.

[(:|)]

Thanks Vinnie.  So I guess the ss109 really isn't all that advantagous unless you're shooting at hard targets beyond 300 yards.
PoliticalScience, that's nice to know.  But I think that given my likely engagement distances  100 < 25yards, the m193 will be more practical.  However, I will keep a mag or two loaded with ss109's just for giggles.  Thanks for your input!

*and don't ask me who's giggles!*  :)

Better penetration at longer ranges is about the only thing I can think of that SS109 (more specifically the M855 versions) would have an advantage at. Otherwise some rifles may be more accurate with SS109 than M193 and this may be an important consideration as well. But if all things were equal and you are most concerned with 0-300 yards, I would likely opt for M193.

-Charging Handle

i would sugest that you not use SS109 for duty use.

little lawyers on each of those steel penetrators.

It is 10 years old and was surplused for a reason, even if we don't know what that reason is. It is reported to run 100 fps or so slower than M855 spec. When it was widely available a couple years back there were reports of failure to extract in 16 inch and shorter barrels. The rims were ripping off the cases.

I love the SB ammo for plinking and targets in my 20 inch Colt. It is very accurate and runs 100 percent. But duty ammo needs to be new, first quality fodder.