Well, I guess no ones referred back to all the info I've put in the AK & AR discussions.:( (I admit they need to be added to one inclusive post but dont know if Gabe or anyone else wanted to make a sticky w/ the Dr. Fackler, Dr. Roberts, & the McPherson data I have.)
We're discussing a lot of differences in barrel length, velocity, and projectile construction, so let's disseminate the facts. (Gabes a brave man for trying to pull this all together!!!)
The current facts on 5.56mm NATO ammo is that the 55gr. M193 and 62gr. M855 loose their optimum fragmentation in the ~2,700fps +/- velocity range per Dr. Fackler & Dr. Roberts information.
The 5.56 OTM (Open Tip Match) rounds or .223 equivalents loose optimum fragmentation in the ~2,100-2,300fps +/- velocity range per Dr. Roberts information. (It seems the heavier the OTM the lower the fragmentation range goes. IIRC, the 100gr. OTM had a ~2,100fps +/- or lower threshold!)
Referencing barrel length information like SMGLee gave is the only way to know at what range Ball (M193/M855) or OTMs will still give their optimum performance.
5.56mm M193 55gr. Ball w/BC .243:
~2,700fps threshold: M16 20= 130yds, 16= 105yds, M4 14.5= 90yds
Neck Length: 3.88
5.56mm Q3131A 55gr. Ball w/BC .267:
~2,700fps threshold: M16 20= 150yds, 16= 125yds, M4 14.5= 105yds
Neck Length: 3.8-4.0
5.56mm M855 62gr. Ball w/BC .304
~2,700fps threshold: M16 20= 120yds, 16= 90yds, M4 14.5= 65yds
Neck Length: 3.54
.223 Blackhills 68gr. OTM w/BC .355
~2,400fps threshold: M16 20= 180yds, 16= 120yds, M4 14.5= 105yds
Neck Length: N/A
.223 Blackhills 75gr. OTM w/BC .393
~2,300fps threshold: M16 20= 205yds, 16= 155yds, M4 14.5= 125yds
Neck Length: 1.57
5.56mm Mk262 Mod1 77gr. OTM w/BC .340
~2,300fps threshold: M16 20= 210yds, 16= 170yds, M4 14.5= 145yds
Neck Length: 1.60
Russian FMJ varies from the country of origin. The older steel encased core ammo is very hard to find or rare. Therefore, most of the FMJ on the surplus market is of the lead core variety. What varies is the jacket thickness at the Ogive of the bullet so base thickness is of little use when trying to determine jacket thickness.
Theres more but I need to organize this stuff together
"If war is ever lawful, then peace is sometimes sinful."
"Me? I think all of that is a load of gun school crap. I train and teach to shoot them to the ground. Beginning at the chest I shoot a burst to the chest and run the line up til I get to the face. Winning their hearts and minds....Suarez style."