Ah, the dreaded dimples. There are several ways to deal with these (according to Remington non-PC) dimples.
The easiest thing is to drill them out. They are covered by the barrel ring so you'll never see the holes.
I can not bring myself to touch my guns with a drill so I opted for another way.
The one's that I've done, I used a socket that just fit into the mag tube as an anvil and flattened the dimples with a ballpeen hammer, dressed it with a dremel, sanded and painted and it looks terrific. Careful not to pound the mag-tube out of round! Both of my Express guns were dimpled originally.
I've read that some folks have had good luck with hones as well.
Some just go at it with the dremel.
The most important thing is to get that tube smoooooth inside so you do not hang up the follower.
After finishing, please write or call Remington to express your distaste of the alleged non-PC dimples.
They will claim that they are a convenience to hold the new style follower. Of course if they had not gone cheap and removed the locking ball-bearing from the barrels so the old caps would hold tight.......grumble grumble mutter mutter........
Note that the police guns (which accept extensions) do not come with these things.
Mike