Gunsmithing Flush cups- What are they for?

[Oneteam]

I know this is a silly question, but I have searched and cannot find the answer.
What are flush cups used for?

 

[bohem]

Re: Flush cups- What are they for?

QD Swivel attachment for sling use in a no-snag setup on the stock.

 

[excess]

Re: Flush cups- What are they for?

Just like Bohem said. They are basically a cylinder with a groove cut on the inside diameter. A sling swivel made to work with them has ball bearings that retract when you push a button, and extend into the groove when you let go of the button, locking the swivel into the flush cup.

 

[Oneteam]

Re: Flush cups- What are they for?

Great, thanks. I knew they were for an attachment of some sorts but I was looking at them on my McMillan stock and just couldn't see why they were there.