Word of warning , you will need a expensive rivet setter to use the tube rivets .
Like someone else mentioned, screws washers and nuts are alot easier to use .
To remove them use a drill bit slightly larger than the rivets drill the "flare" out from the inside and punch the rivets out.
You can refinish your stock or repaint and if the swivel needs rifinished do it while out and then reinstall with screws and nuts .
I use button head cap screws (10-32 ).
I length will vary depending whether your stock is a wood NM or 'glass or standard profile. You can use shorter screws on the glass, but will need some a little longer if the stock is NM.
Hope this helps !