Fun with the EOTech Donut of Death
I love the EOTech holographic weapon sight, particularly the reticle. Tam has dubbed the reticle the donut of death. Here’s a picture of the reticle:
It is a 1 MOA dot inside a 65 MOA circle (for those not in the know, MOA is roughly one inch at a hundred yards). The dot is good for longer shots when accuracy is needed. The circle is good for rapid acquisition when MOA accuracy isn’t necessary. Also, it’s roughly the size of a man (a shorter man) at 100 yards and can be used to SWAG* a range estimate. The reticle also has posts at 12, 3, 6 and 9 which can be useful for a variety of things.
This brings us to fun with my 9mm AR-15. Since I only shoot it at the indoor range and have decided it would make a good house gun, it’s set up for short range work. I have it zeroed in at seven yards (gunnies will know what that number means). On the EOTech, at 7 yards, I put the dot on the target and that’s where the bullet goes. At 7 yards, firing as fast as I want to, it gets groups like this:
Sighting it in at such a short range has disadvantages as most sights are designed for at least 25 yards but mostly 50 to 100. This means that at further ranges, the dot isn’t that useful. So, here’s where the EOTech’s coolness comes in. At 15 yards, I simply place the target I am shooting at between the 12 0’clock hash-mark and the dot like so (X is my target):
And it works. I didn’t take pictures when at the range last but it gets groups of comparable size but slightly larger. A little bounce has more effect the further away the target is. At 25 yards, I place the target at the bottom of the top hash-mark, like so:
It works too. Your mileage may vary.
* Scientific Wild Ass Guess
August 22nd, 2006 at 9:47 am
Looking at your drawings I’d guess that you’re rifle shoots about 7″ high at 25 yards?
If you adjust the sight dead on at 25 yards you should be only about 2″ low at 7 yards. Just sayin’.
August 22nd, 2006 at 9:51 am
Yeah, you people who understand this stuff annoy me. I’m not so good at figuring out optics and ranges.
August 22nd, 2006 at 9:24 pm
According to Joe Huffman’s Modern Ballistics, if you zero it two inches high at 25 yards, you’re about 1.25 low at 7yards, three inches high at 50 yards, about dead on at 75, and seven inches low at 100 yards. (based on 1120 fps, 124 grain 9mm.
If you assume your carbine gets 1400 fps, zero 1 inch high at 25 yards… -1.75″ at 7yards, +2.5″ at 50yards, +1.5 at 75, -3 at 100.
The trajectory matters a bunch past 50 yards or so based on the muzzle velocity. I’d be inclined to, say, split the difference at 25 yards, call it about 1.5ish. You’ll be low until 17 yards or so, high from there until about 75 yards, and slightly low at 100 yards.
Or, just get Modern Ballistics from Joe, and figure it out yourself. 🙂
August 23rd, 2006 at 12:38 pm
7 yds = 21 ft = Tueller Drill