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Author Topic: M21 Optic Question  (Read 454 times)
Jotles
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« on: April 17, 2017, 01:15:42 PM »

Hi there,

I've been running an M21 optic with the picatinny throw lever adapter for about 6 months now and I've started to notice an oddity with how the optic returns to zero after side pressure is applied and just wanted to confirm whether this was normal or not. I'm aware that the W/E adjustments are external and that the optic is designed to attach in a spring-loaded manner to the mount which allows it to take an impact and return to zero. The issue I'm having is that if I put side pressure on the optic it doesn't quite return to zero when I release it, it gets kinda close but needs to be jolted by the recoil of firing a round or 2 or by charging the bolt manually a couple times.

I noticed this when I was checking to see how well it co-witnessed to my irons. If I look at the reticle through my irons and twist the optic to the left and release it, my reticle rests just past the left side of the iron sight, if I do it to the right it rests to the right of the iron sight. Give it a few jolts of force and it returns to the center of the front sight post. I was able to confirm that this threw off my point of impact at the 25 yard line by about 3 inches for the first shot while zeroing which is kinda disturbing because that means it would throw me off by a foot or more at a couple hundred yards out. It doesn't take a lot of force to get this effect either, just a light twist or even setting the rifle down briskly on the optic.

Anybody else have this issue?
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larryz
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« Reply #1 on: April 20, 2017, 09:56:18 PM »

Similar but different.  I've noticed the nuts holding the swivel levers get a little loose, and that throws zero sideways a bit.  Applying a little torque with the TAV-Tool does the trick, though. 

I've decided to tighten up the nuts as much as possible and re-zero at that relative tightness.
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Jotles
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« Reply #2 on: April 20, 2017, 10:35:37 PM »

That was my first thought too.  I cranked down the nuts as far I could get them before they felt like they might start stripping but that didn't seem to help.  I think whatever is going on is happening within the optic itself and not related to the mount.  I did manage to get ahold of Mako and they said it was normal to have to fire a round to reseat the optic after something puts pressure on it but it's really crazy how little pressure it takes to throw off the zero, it literally only takes a light push with a finger...   Shocked
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