What is this thing underneath the scope bottom?

All my scopes have a flag bottom. Then this new scope I order came in and it have this thing on the bottom of the scope at an angle. Not sure what it is but I used a pliers and turn it counter clockwise and it came loose. I kept turning it and there is a spring inside that pushed the whole thing out. I was like wtf lol. I tried to screw it back but the spring was so hard. You have to really push it down and twist it back. Took me awhile but I was able to screw it back. So what the hell is this thing for? Why most scope don't have it and then there is this scope that have it.

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I think you might have just let out all of your nitrogen
Well I didn't see anything inside. Was just the cap and spring I think. I was curious what it was since none of my scope had it so i twist it open to see whats in it Lol.
You removed the cap for the spring that supports the erector tube.

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Scope was brand new. I didn't damage it did I? How come some scope have it and others don't? I have like 5 scopes on other guns doesn't have it. But this new scope I order had it. I don't really like how they install it at an angle and it is sticking out.
 
Well I didn't see anything inside. Was just the cap and spring I think. I was curious what it was since none of my scope had it so i twist it open to see whats in it Lol.

Scope was brand new. I didn't damage it did I? How come some scope have it and others don't? I have like 5 scopes on other guns doesn't have it. But this new scope I order had it. I don't really like how they install it at an angle and it is sticking out.
Some medium and all low mounts that cap/ plug hits the mount and no good ..

Needing to use it I desperation gouged out a old mount to make it work till new mounts that would arrived .lol ( pissed)

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Lol.. it's sad but it worked ..lol
 
Well I didn't see anything inside. Was just the cap and spring I think. I was curious what it was since none of my scope had it so i twist it open to see whats in it Lol.

Scope was brand new. I didn't damage it did I? How come some scope have it and others don't? I have like 5 scopes on other guns doesn't have it. But this new scope I order had it. I don't really like how they install it at an angle and it is sticking out.
If it ain’t broke…..