B-ARFCOM user Molon posted a helluva RDS eval thread which I have yoinked and shared below.
First and foremost, the Aimpoint red dot sight is a combat sight. Its primary purpose is for use in situations that require “reflexive shooting” at multiple targets, at close ranges. The Aimpoint excels in this type of shooting because it easily allows you to shoot with both eyes open and to focus on the target while shooting. All of my self-defense AR-15s have Aimpoints mounted on them. However, should the need arise (for example, making a head-shot on an aggressor at 100 yards who has most of his body behind hard cover) the Aimpoint sight is certainly up to the task of making precision shots.
There are those on this website who claim that when using an Aimpoint sight with a four minute of angle dot, that it is not possible to shoot groups that are smaller than four minutes of angle in extreme spread. One such person has gone so far as to claim that groups shot from 100 yards using an Aimpoint with a 4 MOA dot will be “greater than 4 inches. Usually much greater.” As we shall soon see, such statements are completely false.
To determine the level of precision obtainable when using an Aimpoint sight with a 4 MOA dot, I mounted an Aimpoint ML2 with a 4 MOA dot on one of my Krieger barreled AR-15s. This AR-15 is easily capable of producing consistent sub-MOA 10-shot groups at 100 yards when using a high magnification scope. Shooting with the Aimpoint sight was done from a bench-rest at a distance of 100 yards using NRA 200 yard High Power type targets that I scaled-down for 100 yards. (The aiming black is approximately the same width as a human head.) Sighting was done using the whole dot centered on the bullseye. Three 10-shot groups were fired in a row for evaluation.
Zeroing the Aimpoint sight at 100 yards was conducted during a down-pour with 20-25 mph winds. The first two 10-shot groups were also fired under these conditions. The first 10-shot group had an extreme spread of 1.41”.
With another couple clicks of windage and elevation adjustment, the second 10-shot group had all shots going into the X-ring. The extreme spread for this group was 1.19”.
Just as quickly as the down-pour had started, the rain stopped, the winds died down and the sun began shining again. I posted a new and dry target on the 100 yard backer and continued shooting. The third 10-shot group had an extreme spread of 1.14”. The average extreme spread for all three of the 10-shot groups was 1.25”.
Here’s a little demonstration of the “practical accuracy” obtainable when using an Aimpoint with a 4 MOA dot. For this exercise, I used a 14.5” chrome lined, NATO chambered carbine. Shooting was done from the prone supported position. From a distance of 50 yards, I fired ten quick shots at an FBI “Q” target. The results . . . ten “bullets in the brain pan, squish!”
The 10-shot group has an extreme spread of 1.18”, which at 50 yards is equivalent to 2.26 MOA; far smaller than the 4 MOA dot on the Aimpoint. Again, this disproves the spouted nonsense that “practical accuracy” is not possible when using an Aimpoint with a 4 MOA dot.
Observations On The Effect Of Parallax Error
When Shooting With an Aimpoint Comp M5, a Trjicon MRO and an Aimpoint T2
Some manufacturers of red-dot sights have made claims that their red-dot sights are “parallax free“. Most of us are already aware that this is simply not true at all distances. Inherent parallax error with a red-dot sight is typically greatest at CQB distances (MOA wise) and decreases as the distance to the target increases.
In this ballistic exercise we’ll be looking at the amount of parallax error occurring during objective, controlled, live-fire testing at the distances of 7 yards, 15 yards, 25 yards and 50 yards when shooting with an Aimpoint Comp M5 and a Trijicon MRO mounted on a precision AR-15. The Aimpoint Comp M5 has a 2 MOA red dot, as does the Trijicon MRO.
All shooting for this exercise was conducted from my bench-rest set-up using one of my precision AR-15s. This AR-15 has a 20” Lothar Walther barrel with a 223 Wylde chamber and a 1:8” twist and it routinely produces 0.75 MOA 10-shot groups at 100 yards (with a high magnification scope). The ammunition used for this exercise was one of my match-grade hand-loads topped with the Sierra 52 grain MatchKing. Wind conditions on the range were monitored using a Wind Probe. The set-up was very similar to that pictured below.
The barrel . . .
10-shot group at 100 yards . . .
The Wind Probe . . .
The methodology for this ballistic exercise was as follows . . .
Shooting from the bench-rest set-up with the Aimpoint Comp M5 atop the precision AR-15 at the initial distance of 7 yards, an 8-shot control group was fired with the red-dot centered in the sight window. Next, 8-shot parallax test-groups were fired in the following manner:
2 shots fired with the red-dot positioned in the extreme 12 o’clock position of the sight window.
2 shots fired with the red-dot positioned in the extreme 3 o’clock position of the sight window.
2 shots fired with the red-dot positioned in the extreme 6 o’clock position of the sight window.
2 shots fired with the red-dot positioned in the extreme 9 o’clock position of the sight window.
Additional 8-shot parallax test-groups were then fired sequentially at 15 yards, 25 yards and 50 yards in the manner described above. This simple methodology is illustrated in the two pics shown below. The solid black dot on the target was the point-of-aim.
The 8-shot control group at 7 yards . . .
The 8-shot parallax test-group at 7 yards . . .
Aimpoint Comp M5 Results
The 8-shot control group fired at 7 yards had an extreme spread of 0.039”, which at 7 yards is 0.53 MOA. The extreme spreads of the parallax test-groups are shown in the table below.
Trijicon MRO Results
I repeated the ballistic exercise described above using a 2nd-generation Trijicon MRO with a 2 MOA red-dot. The results are shown in the table below.
I also conducted the 50 yard portion of the parallax test using an additional 2nd-generation Trijicon MRO with a 2 MOA red-dot. The results were nearly identical to that of the first MRO. The extreme spread of the 8-shot parallax test-group was 7.46”, which at 50 yards is 14.3 MOA.
The tables and graphs below show the results from both the Aimpoint Comp M5 and the Trijicon MRO, side-by-side, for comparison.
Results in inches . . .
Per Aimpoint, the objective lens of the Aimpoint CompM5 has a diameter of 18mm. Per Trijicon, the objective lens of the MRO has a diameter of 25mm. Therefore, the objective lens of the MRO is 1.38 times larger than the objective lens of the CompM5. The parallax error of the MRO at 50 yards (7.73”) is 8.3 times larger than the parallax error of the CompM5 (0.93”) at 50 yards.
Results in minutes of angle . . .
Aimpoint T2 Parallax Error At 50 Yards
An 8-shot parallax test-group fired from 50 yards using an Aimpoint T2 had an extreme spread of 0.907″, which at 50 yards equates to 1.7 MOA.
The target shown below is the actual 50 yard parallax-test target for one of the Gen-2 Trjicon MROs that I tested. The parallax error is 7.7 inches. The target also clearly demonstrates the asymmetric parallax pattern of the MRO. I’d like to see someone do the trigonometry for those “hold-offs”, on the fly, in the urban prone position.
Now, let’s superimpose the above parallax-test target on a realistic training target at 50 yards, for both a head-shot and an upper thorax shot. Only three shots out of eight shots hit the head of the target when using the MRO. Only two shots out of eight shots hit the upper thorax of the target when using the MRO.
Here’s the 50 yard parallax-test target for an Aimpoint T2 superimposed on the realistic training target along with the MRO. Every single shot fired using the Aimpoint T2 hit the head of the target and the upper thorax of the target.
Head Shots With Red Dots
For this ballistic exercise, I did a brief comparison of the level of accuracy that I was able to obtain when aiming with four different “red-dot” sights. The following four optics were tested:
> Aimpoint CompML2 with a 4 MOA dot
> Aimpoint T1 with an advertised 4 MOA dot
> Aimpoint CompM4S with a 2 MOA dot
> EoTech 551 with the 65 MOA ring/1 MOA dot
All shooting for this ballistic exercise was conducted from the bench at a distance of 50 yards using my Lothar-Walther barreled AR-15 and match-grade, hand-loaded ammunition. The head-targets used for this exercise were reduced in scale to simulate aiming at distances beyond 50 yards.
The testing was conducted at 50 yards in order to mitigate the variable of wind-drift that would have been significant if testing had been conducted at actual distances and to remove the vertical variation of the points of impact that would have occurred due to bullet drop at actual distances. The objective here was to determine what the limitation on accuracy was, due to aiming with the various red-dot sights, not how well I could dope the wind and distance. Each optic was zeroed for POA=POI at 50 yards prior to testing using 10-shot groups. All aiming was conducted with the entire dot of each optic placed over the head-target. (No aiming was done using just the bottom or top of the dot or holding the entire dot above or below the head-target.)
The targets used for this exercise are copies of the head portion of the Front Sight Official Training and Qualification Target. The Front Sight target is an “accurate representation of human dimensions taken from medical cadaver studies and 3000 x-ray studies.”
Only the head portion of the target was used so that no visual cues could be obtained from the larger body portion of the target. The full-sized head-target is approximately 6” wide by 9” high. The targets were sequentially reduced in scale to simulate the full-sized head targets from 75 yards to 600 yards (at the actual distance of 50 yards), in 25 yard increments. (Again, all shooting was actually conducted at 50 yards.)
The simple test procedure for this exercise was as follows: one shot and one shot only was fired at the head-targets in increasing simulated distance (smaller and smaller targets.) Testing for each optic ended when I missed a target on the first shot. The entire exercise was conducted twice, with the same results each time.
To establish a control base-line of accuracy, I tested a NightForce NXS 1-4X with the NP-1 reticle prior to testing the red-dot sights. Using the NightForce scope (set at 4X magnification) I was able to make first-round hits on the simulated 600 yard head-target (the farthest simulated distance that I used for this exercise.)
Aimpoint Comp ML2
Using the Aimpoint CompML2 with the 4 MOA dot I was able to obtain first round hits on the simulated 225 yard head-target.
Using the Aimpoint T1 with the advertised 4 MOA dot I was able to obtain first round hits on the simulated 250 yard head-target.
Aimpoint Comp M4S
Using the Aimpoint Comp M4S with the 2 MOA dot I was able to obtain first round hits on the simulated 400 yard head-target.
Using the EoTech 551 with the 65 MOA ring/1 MOA dot reticle (and aiming with the 1 MOA dot) I was able to obtain first round hits on the simulated 375 yard head-target.