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I have 2 509 midsize mrd's. I have a Deltapoint Pro and a Holosun 507c x2. Looks like there wont be any issues with the DPP, as the screws that came with the FN fit fine. However, I noticed that although the Holosun uses the RMR plate, the screws provided by FN do not seat properly in bevel of the Holosun due to either the angle or diameter of the head, and the screws that came with the Holosun are different threading than the 509.

I have done my share of research on this, and have not found a solution aside from milling the existing screws to fit. I don't really want to do that. Another solution i've read about if securing with loctite or vc-3. I don't want to rely on just that. My next option is to just return the Holosun and buy an RMR. Does anybody know if the screws provided with the FN will seat properly with the RMR? I do not want to run into the same issue, and know that the screws provided with the RMR are the same threading as the Holosun.

Mildly frustrating. Any pointers would be great.
 

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Have a micrometer, angle gauge and thread pitch gauge? If not Harbor Freight can help with that. Take some measurements and order the correct screws from www.boltdepot.com trust me, if BD doesn't have it, it doesn't exist.
 

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Have a micrometer, angle gauge and thread pitch gauge? If not Harbor Freight can help with that. Take some measurements and order the correct screws from www.boltdepot.com trust me, if BD doesn't have it, it doesn't exist.
I don't have any of those fancy items. I know the thread pitch of both screws. So the angle and diameter of the bolt heads would be the winning ticket. I originally looked at McMaster, and the head diameter was the same on all the 6-40's, so I didn't bother digging any deeper. I'm pretty sure I said "screw it" out loud, and decided it was easier to just buy some RMRs. I'll head to Harbor Freight tomorrow and check the site you recommend. It may help more than just me. I've read plenty of people stating that they stripped threads, the optic came loose, or only 2 threads holding on.

I appreciate you advice. Thank you.
 
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