What Is This?

[agilmore01]

I have noticed this small button hole on the bottom of many scopes and don't know what it's for. I bought this used Primary Arms 3-18x50 scope online, always knowing what you get may not be the best, but I took my chances since it was a decent deal. On the bottom, it appears the small screw or plug that goes in the hole was put in crooked and then grinded down. What are these holes for, and is there a certain tool I can use to get this taken out and put back correctly?

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[celltech]

I believe that is the port where they purge the oxygen and then fill it with nitrogen so the glass won't fog internally. If you pull it the seal is broke. With the wear marks on it they either sent it back for service or pulled it themselves for who knows what. All my Vortex scopes have angled plugs so it's not uncommon..and looking at online pics of that scope they are as well. I would just leave it alone and try to enjoy it....hopefully it works for you.

[Txhillbilly]

More than likely,the previous owner of the scope mounted the scope in rings that were too low for the screw plug to clear the scope mounting rail and ground the end of the plug off for clearance.

[agilmore01]

More than likely,the previous owner of the scope mounted the scope in rings that were too low for the screw plug to clear the scope mounting rail and ground the end of the plug off for clearance.

That's what I am starting to figure.

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[Robinhood]

Good scope for the money. The reason it is at an angle is that it is the return spring part of the suspension system that guides the vertical and horizontal adjustments of the scope.








One would surmise that the screw was making contact on the base and it was filed to allow clearance to align the scope.

[agilmore01]

Good scope for the money. The reason it is at an angle is that it is the return spring part of the suspension system that guides the vertical and horizontal adjustments of the scope.








One would surmise that the screw was making contact on the base and it was filed to allow clearance to align the scope.

This diagram you posted is exactly what I was searching for so that I could visually see what it was for. Thanks!

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[JeepsAndGuns]

More than likely,the previous owner of the scope mounted the scope in rings that were too low for the screw plug to clear the scope mounting rail and ground the end of the plug off for clearance.

Had that exact same issue with a rifle and scope combo. I ended up finding a set of rings in my spare parts box that were just high enough to clear it without grinding it.

[Robinhood]

https://www.primaryarms.com/pa-3-18x...-6-5cm-reticle

There is a pdf manual on this page.