Nikon M223 mount... Sighting in questions

[skidoo j]

About a year ago I purchased a Nikon M-223 scope mount and a 3-12x42 sf scope.

I have sighted it in at 100 yards with the turret on 100 yards and it shoots well. I recently took aim at 400 yards. I turned the turret to the 400 yard hash and was about 2-3' low. turned it back to 100 yards, took aim at 100 yards and dead center.

This scope is designed for 55gr .223 ammo at ... fps the ammo i was shooting and sighted to, matched said specifics. The scope has the Nikoplex reticle...


So my questions:
did all the m-223 mounts when they first came out have the 20moa in the mount and nikon has just relabeled it m223-xr?

Am I supposed to be sighting the rifle differently at 100 yards if the mount has the 20moa? (again i put the cross hair on center at 100 and sighted then popped the turret free and snapped it on the 100 hash and have not popped it free since.)

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[bman940]

Skid, When the M-223 AR Mount first came out they all had 20MOA built into them. Then folks started asking for a mount without the 20 MOA so now we have 2 M-223 AR Mounts. One with (M-223 XR) and one without (M-223). As for your shooting and being 2-3 feet low, a huge difference obviously. While that Nikoplex reticle is built around .223/55 grain polymer tipped bullet at 3240 fps. Some shorter barrel AR's are producing less MV. My 16 in barrel averages 3040 fps. That being said I have still shot it to 600 yards and been able to hit a 10 inch steel gong at that distance.
I have seen guys put this mount on backwards many times, alaways first question I ask, left handers seem to be more likely to do this....
I would suggest going back to 100 yards, shot 3 shots, turn turret to 200 yards, shoot 3 shots, the impact whould be 2.76 inches high, turn to 300 and the impact should be 11.2 inches high. This will give you a good idea if your calibration on scope and your rifle/ammo are functioning as designed. Please keep me posted on progress Skid.

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[skidoo j]

I have the overhang to the rear of the gun. So it looks like the scope is allowed to go further back.

So with the 20moa mount I don't sight it differently?

 

[skidoo j]

Skid, When the M-223 AR Mount first came out they all had 20MOA built into them. Then folks started asking for a mount without the 20 MOA so now we have 2 M-223 AR Mounts. One with (M-223 XR) and one without (M-223).

That's dumb in their nomenclature The new one should have been M-223 FL or M-223-LV rather than changing the name of their old and then giving the old name to a new product. I spent almost an hour reading through their web sight trying to find reference stating M-223 of this age ... It's not like it's a computer and models change weekly, to me it would be like ford changing the name of the Mustang Saleen to Stallion and then renaming the Mustang (Base Model) to Saleen.

 

[speedtriple]

The reason for a 20 MOA mount is for long distance shooting. You sight them in just the same as a level or 0 MOA mount. But it you are shooting long distance, the 20 MOA mount will leave your scope more more vertical adjustment to allow for bullet drop at 600 + yards.

 

[bman940]

There should be no difference in the way you sight in your rifle with the 20 MOA base or a flat base. Like I said earlier, try the bullet drop test to see if your bleeding MV from somewhere. It's just strange you are 2-3 feet off. I look forward to hearing what your results are Skid.