Reflex scope question

[1911copper]

My ignorance in the area of the topic may be a source of amusement for some, but I've got to bite the bullet and ask my question. The reason I never familarized myself with these optics is that I never felt the need for anything more than a tritium sight and maybe a weapon light in the past.
I recently purchased a Meprolight Mepor 21 reflex (red dot) scope. I definitely prefer the use of iron sights, so I set out to find a way to get my reflex scope to cowitness with my iron sights.
The solution that I came up with was to get a riser mount, which elevated the mount for the scope and had a "see through" recess between the dustcover and the scope mount. This riser mount mounts to the flat-top piccatinny rail of my SA58, and is configured with another piccatinny rail on top, atop of which my Mepor 21 mounts.
The problem is that the manufacturer of the riser mount made the base of the mount (which attaches to my dustcover's flat top) about 5 times the thickness that it needs to be, thus, I had to raise my rear sight to its highest setting, and my front post almost all the way. This has apparently allowed the spring under the front post to distort its angle, and cause my shots to go about 4" left at 100 yards.
I'm going to try to have quite a bit of metal machined from the base of the riser mount to fix that problem, however:
The instruction manual for my Mepor 21 scope states that scope is to be zeroed at 25yds, and that at that setting, the weapon will hit "slightly" lower (about 4-5") at close ranges, such as 7yds, and "slightly" higher (about 2' higher ) at 100yds, which the shooter will just have to make mental note of and compensate point of aim for.

I hate this. Is this proprietary to my Mepor 21, or is this pretty much the way it goes for reflex scopes, such as the EOTech?

Please advise. If this is only the case with my Meprolight scope, I'm selling it for an EOTech.

[DJ Niner]

Actually, that's the way it is with ANY sighting device.

When you zero a scope, reflex/dot sight, or even iron sights on a rifle, you are adjusting the sight so the weapon's barrel is angled slightly upward. The bullet crosses the line-of-sight (the straight visual path of light through your aiming device) the first time fairly close to the shooter (at about 20-30 yards, depending on the weapon/caliber), and then as the bullet reaches the top of it's arc, it starts downward and crosses the line-of-sight again (at your selected zero distance, say, 100 yards). At any point after the zero distance, the bullet will now be BELOW the line of sight (shooting low).

The only way to be sure of your bullet's impact point vs. your aiming point is to actually shoot the weapon, with it's normal ammunition, at all (or most) common distances it will be used. Sight-in at 100 yards, then if you think you may have to shoot at, say, 25/50/75 yards, then post a target and shoot at these distances. Aim at the center of the target, and note any change in the point of impact. Jot this down on a piece of paper. Now do the same thing for longer distances (150, 200, 250, and 300 yards). Make similar notes. Finally, type or print it nice and neat in a bold typeface, then take it to a copy shop and shrink it to 20-25% of it's original size, then tape it to the side of your stock with clear packing tape, so it's waterproof. Now you have a quick reference of point-of-aim/point-of-impact at all common distances.

[1911copper]

Originally posted by DJ Niner
Actually, that's the way it is with ANY sighting device.


When I zero my iron sights at 100yds, everything from 0-100yds is point of aim. This reflex scope varies every ten yards.

In boot camp, they taught us that everything from 0-250m was the same dope. (M-16)

[MrMurphy]

Are you keeping a consistent cheekweld? Some dot scopes have parallax, though a Mepro shouldn't.

[1911copper]

Ha! On mine, its more like a "chinweld".

[Nigel_C]

Copper,
What they told you in boot about dope was incorrect.

I had a m21 and liked it.. never co witnessed irons with it though.
I run Aimpoint now with ARMS back up..works sweet.

Ballistics is Ballistics Point of Aim == Point of impact is only true for the distance Zeroed.
CLoser will hit high, to a point than real close you will have hold over to worry about (bore axis vs sight axis)
further than Zero distance will hit low.

Optics, irons or rock tossing.. thats just how it is..

Not a flams, just a fact jack..Remember most of the time in Boot your DS is full of ****. It's basic training...

Later dude and good luck with the meprolight.

[1911copper]

Originally posted by Nigel_C
Copper,
Not a flams, just a fact jack..Remember most of the time in Boot your DS is full of ****. It's basic training...

Later dude and good luck with the meprolight.

Didn't really see it that way, and remember that USMC has the best shooters of all branches, but I take your point.

[DJ Niner]

Originally posted by 1911copper
When I zero my iron sights at 100yds, everything from 0-100yds is point of aim. This reflex scope varies every ten yards.

In boot camp, they taught us that everything from 0-250m was the same dope. (M-16)
If your target is large enough, and all you want is a "hit", anywhere on that target, then what they told you is BASICALLY correct, but not SPECIFICALLY correct. If you carefully aim the weapon at a specific point on the target, and compare that aiming point with the impact point of the rounds at varying distances, then what I told you will be true. MOB (minute-of-body) shooting is what your DI was talking about, and he was also trying to "keep it simple" so it would be easy to remember. And it worked; you remembered it.

The instructions with the Mepor 21 sight were correct, but the exact distances and measurements (like 2" high at 100) will vary a bit based on how high above the barrel the sight is mounted, etc. They were probably just speaking of how the average Mepor user sights-in and uses the sight. But again, the specifics may vary, but the concept will not; ANY sight you use, when used properly, sighted-in properly, and used on an accurate weapon will show the effects I outlined. No exceptions that I'm aware of at this time.

[1911copper]

Yes, I think the problem is the amount of height that the scope is mounted on this weapon to allow iron sights to co-witness. I'm becoming more and more frustrated with this approach. I ordered a tritium front post for the gun tonight, despite what DSA says about it being too thick. I'll give it a shot. If I could make iron sights work, everything would be simplified. I never had any problem making iron sights work beyond skill level. They'll shoot as straight as most of US can shoot.

[MrMurphy]

Don't use the cowitness mount, use QD rings and get the scope down on the rifle. If it does bust (highly unlikely), 3 seconds and you're in action with irons.