Paul Gomez
www.Gomez-Training.com
OK, opinions are like assholes, etc, etc...but I'd really like to get some perspectives on zeroing the AR/M4 platform.
The US Army has traditionally gone with a 250M zero on the M16A1 and a 300M zero on the M16A2 and M4.
The 250M zero on the M16A1 [achieved by using the L aperture and sighting dead-on at 25M] has the bullet crossing line of sight at 25 meters, reaches a maximum ordinate of about 11 inches at 225 meters, and crosses line of sight again at 375 meters. When the unmarked aperture is flipped up, you have a 42M initial intersection, a 5 inch maximum ordinate at 175M, and a second intersection at 250M.
The 300M zero on the M16A2, you wind up with a maximum ordinate of approx 6 inches at 175M. It's just shy of 4.5 inches high at 100M.
When using an M4, maximum ordinate jumps to just over 7 and at 100M, around 5.3.
When you look at a 50M/200M zero, out of an actual M4, you have a maximum ordinate of approx 2.10 at 125.
My thought on zero distance is that the acceptable group size doesn't change based on range to threat. In other words, the same 'fist sized group, in appropriate location on threat, as quickly as I can place it' still applies.
To that end, I am willing to accept a 6", plus or minus, area of impact. That means that Maximum Point Blank Range is defined as the point where the projectile is no greater than 3 inches above or below our Point of Aim.
To that end, both the 50M and the 100M zero are acceptable.
A lot of dialed in guys recommend a 100yd or meter zero and I've heard several different explanations for it. Paul Howe likes it because it forces guys to get used to shooting at a greater distance. However, if you read his article on this, he actually prefers the gun to print three inches high at 100yds. That's not exactly a 100yd zero as the term is commonly used.
Another reason given, is that there is less variation from muzzle to 100yd/m when using the 100yd/m zero. In other words, the bullet will impact at slightly less than POA at all points prior to 100 whereas with a 50M zero you have both lower and higher POI within the first 100M.
Of course, if you are using an optic, particularly something with a BDC, the 100 distance has more going in its favor.
Here's some data from a friend showing 50yd and 100yd info for XM193 55grFMJ from a 16-inch M4.
100 yard zero for xm193 from 16" bbl (55gr at 3050fps) at 75 deg F, distances in yards not meters
Range Impact
0 -2.5
25 -1.49
50 -0.73
75 -0.23
100 0
125 -0.07
150 -0.44
175 -1.14
200 -2.19
225 -3.59
250 -5.39
275 -7.59
300 -10.22
325 -13.31
350 -16.89
375 -20.97
400 -25.61
50 yard zero, same ammo and conditions
Range Impact
0 -2.5
25 -1.13
50 0
75 0.86
100 1.46
125 1.75
150 1.75
175 1.41
200 0.72
225 -0.31
250 -1.75
275 -3.58
300 -5.85
325 -8.57
350 -11.79
375 -15.52
400 -19.79
Regardless of the zero you choose, you absolutely must shoot the gun at range and verify how it prints. And everyone gains by extending the range and practicing with a less forgiving target.
The US Army has traditionally gone with a 250M zero on the M16A1 and a 300M zero on the M16A2 and M4.
The 250M zero on the M16A1 [achieved by using the L aperture and sighting dead-on at 25M] has the bullet crossing line of sight at 25 meters, reaches a maximum ordinate of about 11 inches at 225 meters, and crosses line of sight again at 375 meters. When the unmarked aperture is flipped up, you have a 42M initial intersection, a 5 inch maximum ordinate at 175M, and a second intersection at 250M.
The 300M zero on the M16A2, you wind up with a maximum ordinate of approx 6 inches at 175M. It's just shy of 4.5 inches high at 100M.
When using an M4, maximum ordinate jumps to just over 7 and at 100M, around 5.3.
When you look at a 50M/200M zero, out of an actual M4, you have a maximum ordinate of approx 2.10 at 125.
My thought on zero distance is that the acceptable group size doesn't change based on range to threat. In other words, the same 'fist sized group, in appropriate location on threat, as quickly as I can place it' still applies.
To that end, I am willing to accept a 6", plus or minus, area of impact. That means that Maximum Point Blank Range is defined as the point where the projectile is no greater than 3 inches above or below our Point of Aim.
To that end, both the 50M and the 100M zero are acceptable.
A lot of dialed in guys recommend a 100yd or meter zero and I've heard several different explanations for it. Paul Howe likes it because it forces guys to get used to shooting at a greater distance. However, if you read his article on this, he actually prefers the gun to print three inches high at 100yds. That's not exactly a 100yd zero as the term is commonly used.
Another reason given, is that there is less variation from muzzle to 100yd/m when using the 100yd/m zero. In other words, the bullet will impact at slightly less than POA at all points prior to 100 whereas with a 50M zero you have both lower and higher POI within the first 100M.
Of course, if you are using an optic, particularly something with a BDC, the 100 distance has more going in its favor.
Here's some data from a friend showing 50yd and 100yd info for XM193 55grFMJ from a 16-inch M4.
100 yard zero for xm193 from 16" bbl (55gr at 3050fps) at 75 deg F, distances in yards not meters
Range Impact
0 -2.5
25 -1.49
50 -0.73
75 -0.23
100 0
125 -0.07
150 -0.44
175 -1.14
200 -2.19
225 -3.59
250 -5.39
275 -7.59
300 -10.22
325 -13.31
350 -16.89
375 -20.97
400 -25.61
50 yard zero, same ammo and conditions
Range Impact
0 -2.5
25 -1.13
50 0
75 0.86
100 1.46
125 1.75
150 1.75
175 1.41
200 0.72
225 -0.31
250 -1.75
275 -3.58
300 -5.85
325 -8.57
350 -11.79
375 -15.52
400 -19.79
Regardless of the zero you choose, you absolutely must shoot the gun at range and verify how it prints. And everyone gains by extending the range and practicing with a less forgiving target.
?) an optic on top of an A1/A2 carrying handle.
