Sig 556R Ballistic Chart / Zero with ACOG and Aimpoint

[Wiseguy04]

​Tried researching the best data for zeroing the Sig 556R, but found very little, so decided to do my own homework and testing.

Two conclusions, after range testing:

1.) Zeroing at 100yds vs 100m with the ACOG makes very little difference.

2.) The best “Battle Zero” for a red dot on the 556R is 36 yds (200 yds).

First off, these were my calculated drops, for 123 grain ammo, with a 3” height over bore (TA33 ACOG on ADM mount):

Zero distance: 100 yds / 100 m
10 yds: -2.3705 / -2.3595 (.01)
15 yds: -2.0854 / -2.0691 (.02)
20 yds: -1.8168 / -1.7951 (.02)
25 yds: -1.5650 / -1.5380 (.03)
50 yds: -0.5675 / -0.5137 (.05)
75 yds: -0.0329 / -0.0478 (.01)
100 yds: -0.0012 / -0.1064 (.11)
200 yds: -5.8616 / -5.6466 (.22)
300 yds: -24.2808 / -23.9585 (.32) -2’
400 yds: -60.6459 / -60.2163 (.43) -5’
500 yds: -121.8866 / -121.3498 (.54) -10’
600 yds: -215.0953 / -214.4513 (.64) -18’
700 yds: -346.9150 / -346.1639 (.75) -29’

As you can see, the difference in zeros at 100yds/100m is less than a tenth of an inch, and at 700yds/700m, it’s still less than an inch. So no factor there. All the BDC marks on the TA33 worked as advertised. If you’re limited to one of those 25 yard indoor ranges, you can adjust the point of impact to be 1.5” low and be in the ballpark, but you’ll still need to verify it at a longer range when able.

Next, I wanted to get a decent 0-300 yard zero for the red dot (Aimpoint T1 on an ADM mount, 3” height over bore). Looking at ballistic charts for the same ammo, I ended up going with a 36yd/200yd zero, which I believe is what the Marines use for M-4s (ironically). It kept it on a man-sized target for all ranges in the 0-300 yard block:


36 yard / 200 yard Zero
5 yds: -2.52
7 yds: -2.34
10 yds: -2.07
15 yds: -1.64
20 yds: -1.22
25 yds: -0.83
36 yds: -0.01 (Zero)
50 yds: +0.91
75 yds: +2.18
100 yds: +2.94
122 yds: +3.17 (Highest)
200 yds: +0.02 (Zero)
300 yds: -15.46 (1.3’)

Point of impact was roughly 2” low for CQB shots (<25 yard), about 3” high at 100, on at 200, and a little over a foot low at 300. A 36 yard zero seemed to be the ticket.

Hope this helps for anyone still using a very niche platform.

[KarlinPhoenix]

Thank you for this information.

[Dorkface]

What ammo did you use?

[Wiseguy04]

What ammo did you use?

PMC Bronze, so my groups were a bit large. My range only went out to 300 yards, but honestly, further than that and it becomes more like patterning a shotgun (with this ammo). I’ll try again someday with Federal or Lapua if I can find it.