The Firing Line Forums - View Single Post - Who manufactures 9mm &5.56 Ammo for the U.S.

Troy · March 19, 2001, 08:42 PM

The original .223/5.56mm M16 ammo is M193, and uses a 55gr FMJ bullet. The newer, "enhanced long-range penetration" bullet is called M855, and uses the 61.5gr SS-109 FMJBT bullet with a mild steel penetrator sitting on a lead core. This bullet was designed by FN for use in the M249 SAW, and was adopted for use in the M16 during the "A2" update.

Because of the compound core of the SS-109 bullet, the bullet is quite a bit longer than a leadcore 62gr bullet would be, and requires a faster rifling twist of about 1:9. However, the US military also adopted a new tracer round (M856) which is longer still, and would ideally need a 1:5 twist. So, they compromised and went with a 1:7 twist for the SAW, and later for the M16A2.

The original M16s and M16A1s had a slower 1:12 twist which will not stabilize the longer SS-109 bullets, which keyhole after about 95 yards. In order to identify this ammo so it isn't accidentally used in M16s & A1s, M855 has a green bullet tip. The old M193 ammo works fine with the faster twist rate of the M16A2s, A3s, and A4s, though it can be a bit less accurate, as it takes a bit longer for the bullet to "settle" into a smooth rotation.

For most "combat" purposes, M193 is actually better than M855 for the M16. Because velocities are higher with M193, it has MORE penetrating power close-in, and has a longer range until the bullet drops below 2700fps, below which usually it won't fragment in tissue. M855 is better for very long ranges, and punching through light cover at longer ranges, but when you've got people shooting back at you, you'll be more concerned about the close-in performance than the long-distance shots. Besides, that's what the SAW is for...

-Troy

March 19, 2001, 08:42 PM	#7
Troy Member Join Date: January 29, 2000 Posts: 96	The original .223/5.56mm M16 ammo is M193, and uses a 55gr FMJ bullet. The newer, "enhanced long-range penetration" bullet is called M855, and uses the 61.5gr SS-109 FMJBT bullet with a mild steel penetrator sitting on a lead core. This bullet was designed by FN for use in the M249 SAW, and was adopted for use in the M16 during the "A2" update. Because of the compound core of the SS-109 bullet, the bullet is quite a bit longer than a leadcore 62gr bullet would be, and requires a faster rifling twist of about 1:9. However, the US military also adopted a new tracer round (M856) which is longer still, and would ideally need a 1:5 twist. So, they compromised and went with a 1:7 twist for the SAW, and later for the M16A2. The original M16s and M16A1s had a slower 1:12 twist which will not stabilize the longer SS-109 bullets, which keyhole after about 95 yards. In order to identify this ammo so it isn't accidentally used in M16s & A1s, M855 has a green bullet tip. The old M193 ammo works fine with the faster twist rate of the M16A2s, A3s, and A4s, though it can be a bit less accurate, as it takes a bit longer for the bullet to "settle" into a smooth rotation. For most "combat" purposes, M193 is actually better than M855 for the M16. Because velocities are higher with M193, it has MORE penetrating power close-in, and has a longer range until the bullet drops below 2700fps, below which usually it won't fragment in tissue. M855 is better for very long ranges, and punching through light cover at longer ranges, but when you've got people shooting back at you, you'll be more concerned about the close-in performance than the long-distance shots. Besides, that's what the SAW is for... -Troy