I found a Remington 1100 at the local pawn shop yesterday.  It came with 21" smooth bore rifle sight barrel and scope mount/ red dot.  It was in good exterior condition but problems inside.   I got it out the door for $270 including a plastic hard case.  The piston/ piston seal were rusted stuck inside the barrel.  The barrel was tough to remove.  Well I used a barrel brush and oil and cleaned up the rust.  I added a new o ring too.  Picked up a +3 Remington mag tube extension this morning.  I will probably take scope mount off and get gas piston upgrade.  It's my first auto, I have several pumps.  Not sure if was a good deal but I am happy.  Here is obligatory pic. Attached File

Good deal, I had one with the 21" slug barrel and it was a hammer.

I'd take that "sight" off and throw it back in the cast off drawer, strip the furniture and oil it, and bead blast/parkerize all of the metal.

That's a great deal. A new piston and seal are cheap.  

The metal and wood look like they are in very good shape.

I took the 1100 to the range yesterday.  Only had two fail to ejects out of forty, both cheap low brass Winchester targets.  It was fun to crank shots out faster than my pumps.  I had a problem loading though.  I had added a Remington +3 extension before.   I check for dimples and there are none but still can't load more than four in the tube.   It has the original plastic follower in it which I will replace I think with a Scattergun one.   I cleaned the mag tube also.  Any other suggestions to be able to load seven?

I'll assume you've had the follower completely out of the gun so you know that the follower can clear the end of the tube (no dents or dings to hang it up).

The extension tube is likely a 2 piece thing (coupling nut and tube). Disassembly those 2 parts. Screw the extension tube coupling nut on to the gun so it holds the forearm tightly in place. Now insert the follower and spring, then screw the extension tube into the coupling nut until it bottoms out against the gun's mag tube.

This assembly method should ensure there is no gap between the end of the gun's mag tube and the extension tube; a gap there can let the spring or follow hang up and limit capacity

I picked up up a $165 rusty 870 express magnum couple years ago.. after some action work, polishing out the dimples and a new finish of rattle can ceramic engine paint, it's a beast... I ruv pawn shops.

Yep our agency took off all the factory extensions because of the hang ups.  Five reliably is better than maybe eight.   These were factory police 870s that came with factory extensions.

I had the follower out it looks original and worn.  Ordered the Scattergun follower this morning.  I stopped by the LGS this morning.  I found a 28" vent rib rem choke blued barrel on their orphan barrel rack for $70 otd.  Feel lucky on that, eBay barrels are a lot more expensive.

Damn! I bought a 26" vent rib rem choke blued barrel from an individual for $80 and thought it was a steal.

Nice deals OP. If it was me, I'd take the red dot and mount off, sell them(there's bound to be somebody who would want them) and turn the $270 shotgun into a $235 shotgun.

Got a similar setup. Bought a well hunted 1100 for $250 with a Mod choked vent rib barrel. Found a Rem Choke slug barrel (with a rifled choke) for $25 and ordered a Remington plus 4 extension then relaced the stock sights with Tru-glo steel sights and the choke with a Carlson's extended IC choke. Upgraded the piston ring and new O ring. Throws cheap slugs to POA like a pussy cat! And I have the benefit if having a beater bird gun too. It's not pretty but it's killed a shit ton of dove.

Check the extension for burrs in the tube and when you are screwing the tube into the nut with the spring inside give it a couple raps to free the spring from binding before it's seated.