What is the difference between the 55 Gr. and 62 Gr. .223 round? Is one  a better performer than the other.

Since the ammo oracle is down I be breif.

The 55gr M193 is copper jacketed with a lead core running 3250fps @15' from a 20" rifle.

The 62gr M855 is copper jacketed with a steel penatrator and a lead core.  It runs 3025fps @78' from a 20" rifle.

As to better performance?  It depends on your criteria for better.  Some points to ponder on this can be found here: [url]http://groups.msn.com/TheMarylandAR15ShootersSite/ammofaq.msnw[/url] (3rd Q&A down)

I will try to keep this short and to the point....if you want a general purpose round for self defense, plinking, etc, buy the M193. On the other hand, if your most important requirement is the penetration of a steel army helmet at 600 yards, then go with M855. The M193 is cheaper, easier to find and in many cases outperforms the M855 when it comes to fragmentation and wounding ability. There are so many variations in the SS109 bullet (mainly the jacket and whether the steel insert is centered or off to one side) that performance varies from brand to brand and maybe even lot to lot. On top of this, the M193 round is faster, therefore the bullet will stay at or above the 2700 fps velocity threshold farther out. From a 20" barrel the M193 may still be fragging out to about 200 yards, whereas the M855 may only frag out to 150 yards or less. If it was my money, I would buy M193 every time.

-Charging Handle

Excellent. Thanks guys!

Twist rate will determine which will perform better in your particular gun.