I've used a second generation M68 on an M4 with the backup iron sights (BIS) and a ’spacer’ to elevate the optic to coincide with the tall rear sight aperture. I've been told conflicting reports on where to establish the impact zone. I've heard center mass, within the circle and I've heard on the lower portion of the zero silhouette. Which case is correct and what is the purpose of zeroing on the lower portion of a zero silhouette, if that is the case. Also, which zeroing process applies to the M16 when using an M68 on the rifle (center mass or lower portion)?
Thank you for your time

Mr. Delarosa,

Thank you for your question and the opportunity to assist you. I have forwarded your question to the Army Marksmanship Unit for a response.

Until they respond please review The Small Arms Integration Book (SAIB) dated Jan 06 page 71-72

and FM 3-22.9 page 8-12 thru 8-15 which discusses the CCO :

Once again thank you for your question and the use of Warrior University. We hope to have the answer to your question soon.

Respectfully,
The Warrior University Team

Mr. Delarosa,

The AMU's Service Rifle Team states:

For an M4 equipped with CCO the point of aim = point of impact for a 300m zero on a standard 25m target.

For a M16 equipped with CCO the point of aim should be 1.5 boxes above the point of impact on a standard 25 m zero target to achieve a 300m zero. ( you should group in the lower half of the circle)

The Service Rifle Team also stressed that to be truly zeroed for 300m you need to fire a known distance range and confirm.

The M16 rifle has a longer barrel and higher muzzle velocity thus a slight different trajectory than the M4and the need for different points of impact to zero at 25m

The point of aim=point of impact at 300m for both weapon systems and thus the weapons would be zeroed.

If you still have a question please let us know. Thank you for using Warrior University and for your service.

The Warrior University Team