It says to sight it in at 40yrds. So I would think you would be fine out to 100yards with it.
1 MOA = 1.047 inches rounded down (more precisely 1.047197580733 inches) at 100 yards.
A 6 MOA dot is 0.06282 inches per yard.
At 600 yards a 1x 6 MOA dot is covering 37.692 inches of target.
At 500 yards a 1x 6 MOA dot is covering 31.41 inches of target.
At 400 yards a 1x 6 MOA dot is covering 25.128 inches of target.
At 300 yards a 1x 6 MOA dot is covering 18.846 inches of target.
At 200 yards a 1x 6 MOA dot is covering 12.564 inches of target.
At 100 yards a 1x 6 MOA dot is covering 6.282 inches of target
At 50 yards a 1x 6 MOA dot is covering 3.141 inches of target.
At 40 yards a 1x 6 MOA dot is covering 2.5128 inches of target.
At 25 yards a 1x 6 MOA dot is covering 1.5705 inches of target. (7 times larger than 5.56 bullet diameter at .224 inches)
comparison:
A 1 MOA dot is 0.01047 inches per yard.
At 600 yards a 1x 1 MOA dot is covering 6.282 inches of target.
At 500 yards a 1x 1 MOA dot is covering 5.235 inches of target.
At 400 yards a 1x 1 MOA dot is covering 4.188 inches of target.
At 300 yards a 1x 1 MOA dot is covering 3.141 inches of target.
At 200 yards a 1x 1 MOA dot is covering 2.094 inches of target.
At 100 yards a 1x 1 MOA dot is covering 1.047 inches of target
At 50 yards a 1x 1 MOA dot is covering 0.5235 inches of target.
At 40 yards a 1x 1 MOA dot is covering 0.4188 inches of target.
At 25 yards a 1x 1 MOA dot is covering 0.26175 inches of target. (1.1 x larger than 5.56 bullet diameter at .224 inches, almost the same size)
From the above we can see that a smaller dot is better for precision hits and allows longer range use of the dot than a 6 MOA dot would allow. Another thing to consider is how big the target area appears from the shooter point of view at those ranges vs how much of the target is obscured by the dot.
The smaller the target appears from the shooters view point the more of the target area will be covered by the dot. For example, if the target area appears to be between 2 to 3 inches in size from the shooters point of view at 50 yards then the entire target area would be completly obscured by the 6 MOA dot and the target boundaries not viewable for reference. On the same target at 50 yards with a 1 MOA dot the target area covered is 0.5235 inches and the rest of the target area remains viewable allowing for target boundary reference which increases capability for precision hits at chosen specific spots within the target area boundary.
To account for normal vision resolution vs depth preception with a 1 or 2 MOA dot for anything over 100 yards round up to the next higher whole inch number for estimation.
To account for normal vision resolution vs depth preception with a dot size greater than 2 MOA for anything over 100 yards round up to the next higher whole inch number plus 0.5 for estimation.
