Anyone out there ever chronograph any M855 5.56 mm rounds from a short barreled M4 carbine?

Every place I have contacted (Sierra, Black Hills, etc.) gives me velocities that are so disparate (up to 350 fps difference) that they are of little use.

The M855 uses a 62 grain FMJ boattail with a BC of .307...that much everyone seems to agree on.

Thanks,

Rick

Let me guess where you are going with this.....

You want an accurate MV so that you can build some ballistic tables with the use of some software like Sierr Infinity?

If so, don't bother. M855 is very poor in the accuracy department due to the difficulty in locating the steel penetrator concentric with the lead slug and copper jacket.

3 to 4 MOA is about as good as it gets with that stuff.

Just use the distance marks on the elevation drum. Remember they are in meters, not yards.

Wrong guess!

My son is in Iraq and that is the only ammunition they have available to them. They have 300 yard battle sites on their weapons and he wants to use his ballistics software to have an idea of the vertical spread over that distance.

Since the ballistics programs don’t have the M855 rounds in their data bases he has to enter all the info and he just needs a good “ballpark†figure for the velocity from the M4’s.

Obviously, not a huge thing...but I told him I would check and see if I could get the info for him.

Rick

I have the milspec data for all US military ammo from the M2 Ball to the present at home.

I'll post the GI spec MV for M855 tonight when I get there. Not only that, I'll run it through my Infinity program and post the trajectory every 25 yards out to 400 yards (or however far you would like me to).

Hope your son comes back safe and sound.

Wow...thanks so much!

That is certainly far more than I was looking for.

I will pass along your kind wishes to him and his guys!

If you need it for your program...the elevation in Baghadad is approximately 110 feet...and the temperature right now is probably in the high 70’s but will soon get up to triple digits. The M4’s have 14.5 inch barrels and the sights are “around†2 ⅛ inches above the bore center I believe.

Thanks again!

Rick

US M855 (source: US Army TM 43-0001-27)
Muzzle velocity: 3025 FPS.
Projectile: 62 grain FMJ lead/steel core.
Propellant: WC 844, 26.1 grains.

Trajectory assuming 300 yard zero, 100 deg F, sea level. (source: Sierra Infinity ballistics program)

distance (yards) rise(+)/drop(-) (inches)
0 -2.25
50 +1.34
100 +3.85
150 +5.15
200 +5.07
250 +3.43
300 0.00
350 -5.47
400 -13.3
450 -23.8
500 -37.5

HP Shooter,

I can’t thank you enough...I will pass this along to my son.

Thanks, again!

Rick