Opinions wanted for red dot sights

[Daltex1]

I just purchased a smith wesson mp15t ar 15, was wanting opinions on laser sighting systems for it, any info would be appreciated..

[txinvestigator]

I just purchased a smith wesson mp15t ar 15, was wanting opinions on laser sighting systems for it, any info would be appreciated..

What is your intended use?

My favorite is the Eotech as I am set up for close quarters mostly put to 100 yards, but with the Eotech I can hit out to 300.

You can use a flp up rear sight to use in case you have a problem with the optic.

The center dot is 1 MOA, meaning it covers 1 inch at 100 yards. The outer rong is 65 MOA. In CQB you put the outer ring on the target and fire. It is designed for both eyes open shooting.

At 300 yards the center dot only covers 3 inches. The outer ring can be used for rough range estimating. The average man is 69 inches tall. If you target a man at 100 yards and the figure is just larger than or right at the height of the outer ring, you know you are at about 100 yards.


This is the eotech;


and with the flip up rear site;



If your shooting will be mostly long range look at the ACOGS; http://www.trijicon.com/user/parts/part ... tegoryID=3


And I have yet to try a tri-power, but they look interesting to me;
http://www.trijicon.com/user/parts/part ... egoryID=11

[jimlongley]

My HoloSight failed at the start of our three gun match yesterday, I found myself real happy with my co-witness Mangonels - they flipped right up and I was shooting great groups with them all day.

Next time I make sure I have fresh batteries in the HS before the match.

I set my sights point blank at 200, which puts them right on at 50, lower closer than 50 and higher from 50 to 125.

[Alric]

I set my sights point blank at 200, which puts them right on at 50, lower closer than 50 and higher from 50 to 125.

I'm new to rifle sighting, and I'm not understanding that at all. If you sight in at 200, how is 50 going to be right on? I thought if you sighted in at 200, 200 would be right on, and closer would be lower, further be higher?

[Mithras61]

I set my sights point blank at 200, which puts them right on at 50, lower closer than 50 and higher from 50 to 125.

I'm new to rifle sighting, and I'm not understanding that at all. If you sight in at 200, how is 50 going to be right on? I thought if you sighted in at 200, 200 would be right on, and closer would be lower, further be higher?

Think in terms of a long curve. At 50 and 200 yards, the bullet's trajectory are crossing the straight line of sight (rising at 50 and falling at 200). Closer than 50 or further than 200 the bullet will be below line of sight. Between 50 and 200, the bullet is above line of sight.

[jimlongley]

There is also the sight offset from the bore line to consider. In an AR with the original sights, that would be about 2.5 inches, so the bullet has to climb (bad term ,it's not actually climbing, it's just sighted in so that it gives the appearance of rising) until it intersects the bore line.

Since gravitational acceleration starts having an effect on the bullet the very moment it leaves the bore, it is falling at a rate of 32feet per second per second (not a typo) so thoeretically it might be possible to sight in your gun so that it took 600 feet for it to rise to the bore line (and this is a thing to strive for with very flat shooting high velocity rounds), but practically it's better to use the trajectory to your own advantage and improve chance for hits over a wide variety of distances.

So, with the 2.5" offset and the bullet crossing the bore line going up at about 50 yards, at every range from zero to 50 yards the shot will be slightly low (2.5" at the muzzle and reducing to 0 at 50 yards) . Then from 50 to 200 yards (give or take some wind and stuff, this is a good thing to test for) the bullet is up to about 6" above the bore line, and then it drops back below, falling to something on the order of 12" and more by 300 yards. The trajectory is a reducing radius curve, with the bullet slowing down and dropping faster due to gravitational acceleration until it finally hits the ground. Sighted in this way I can get reliable hits on a man sized target, or I could if I could see that far and not shake so much, right out to the maximum effective range of the round fired.

The sight offsets for my Garand and Springfield are much smaller, and the trajectory of those relatively heavy and slow moving bullets (RELATIVELY!) is a huge curve in comparison and necessitates a whole different ballistics table.

And of course each load will produce different ballistics, so the best thing to do is start with a table for a meatball approximation and work slowly to your desired point.

These same "rules" apply to handguns also, they just do it at shorter ranges.
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Having said all that, the same "rule" would apply no matter what sight you were using, making me thankful that I put so much effort into making sure that my iron sights and HoloSight were co-witnessed within the bounds of human effort.

Don't take any of the above to indicate that I am some sort of super marksman, I have done a lot of training and studied guns most of my life, but the difference between theory and application can amount to a very large gap.

[Alric]

Thanks for that. Like I said, I'm really new to rifle sighting and real applications of trajectory. Reading that made a lot of things click, I think.