M4 M855A1 muzzle velocity
- Thread starter Roboss
- Start date
- Status
Neither. Wikipedia is not a reliable source of ballistics information .
https://www.americanrifleman.org/ar...ng-the-army-s-m855a1-standard-ball-cartridge/
https://apps.dtic.mil/dtic/tr/fulltext/u2/a549416.pdf
Jim Watson
Member
1. Wikipedia is a secondary, maybe tertiary source, don't believe anything but generalities.
2. Velocity variation is such that 15 fps is lost in the noise, statistically insignificant.
3. A 2012 DOD paper shows the 2970 value.
2. Velocity variation is such that 15 fps is lost in the noise, statistically insignificant.
3. A 2012 DOD paper shows the 2970 value.
Dain Bramage
Member
Both sets of Wikipedia units seem to round to the "tens". If you followed that convention, then your conversion back from SI would result in 2990 ft/s. So you see how a few rounds of calculations can lead to ever increasing rounding errors. That's why serious math controls number of units, and promises precision only to it's weakest data.
Also, none of them is "exactly" M4 muzzle velocity. One is a government released average value and the other is a lackadaisical conversion to another set of units.
Also, none of them is "exactly" M4 muzzle velocity. One is a government released average value and the other is a lackadaisical conversion to another set of units.
Demi-human
maybe likes firearms a little bit…
As Jim said, 15 FPS difference between two shots doing around 3000 FPS is no difference at all...
And likely not the velocity your barrel will give you anyway.
And likely not the velocity your barrel will give you anyway.
Yup, especially considering that the vast majority of AR's have barrels that are 1.5" longer than that of an M4.
Somebody did the math to convert fps to mps and rounded off.
If you picked up a dozen seemingly identical rifles and measured the velocity of all of them they'd all be somewhat different. And there could be 100 fps difference between the fastest and slowest. 15 fps is nothing to worry about.
If you picked up a dozen seemingly identical rifles and measured the velocity of all of them they'd all be somewhat different. And there could be 100 fps difference between the fastest and slowest. 15 fps is nothing to worry about.
mokin
Member
A couple of years ago I chronographed some surplus ammunition out of my M-4gery with a 16 inch barrel and .224 Wylde chamber. The average velocity of ten rounds was 2925 fps. This was at roughly 6200 feet altitude. YMMV.
GBExpat
Member
benEzra
Moderator Emeritus
Velocity will vary based on bullet weight, SAAMI vs NATO spec, etc.
I assume the 2970 ft/sec number is for either a 55gr or 62gr load in a 14.5” barrel. For 77gr, you’re looking at 2340 to 2690 ft/sec depending on manufacturer and spec.
What can I say. I am young and stupid.Welcome to THR, Roboss!... but ...
Really?
Demi-human
maybe likes firearms a little bit…
But less so now.
There aren’t any dumb questions.
Some are less thoughtful than others, but they weren’t held against me.
So we’ll not hold it against you either...
15 FPS difference is insignificant, ammo from the same run can vary that much.
briansmithwins
Member
- Joined
- Aug 1, 2005
- Messages
- 4,631
How hot or cold was it that day? What elevation was the testing conducted at? What was the relative humidity?
There’re a lot of environmental variables that’ll give you small velocity variations even from the same lot of ammo.
BSW
There’re a lot of environmental variables that’ll give you small velocity variations even from the same lot of ammo.
BSW
- Status
