So I just got a Remington Model 11 from a buddy. It has a 26 or 28" barrel, finish is okay, not a museum piece or anything. From my research, it was MFG'd in October 1946 ( "ERR" date code). The only reason I took this in trade was because I had the intention of cutting it down to 18" and eventually SBS'ing it. My buddy's dad owns a gun shop and can cut the barrel down and add a bead front sight for $75. My question is, should I really do this? Would I be ruining this gun that's actually worth something, or is it just a run-of-the-mill shotgun and doesn't really matter? Also, are extended magazines available for these? It has a screw-type plug on the end that holds the barrel onto the magazine tube, it's not the cap version. It actually threads into a hole in the front of the mag tube, not onto it.

It's well worn but looks very usable.
It's yours do what you want.
I would find a second barrel and keep the best, chop the worst one, and be that much father ahead in the long run.

I had considered doing the same a while back but haven't found the right deal on the right gun.  There are a few nice examples here on arfcom so maybe someone with more knowledge will come along with more info on cutting them back.  I had two concerns.  One was the fiber buffer in the rear of the receiver.  They tend to degrade.  If yours is fine then it's not a problem.  But if they do degrade badly, the gun will beat itself to death.  From what I gather, the first sign of a problem will be a crack starting at the rear of the charge handle slot.  The second worry was that since these are long recoil operated guns, I worried about removing too much mass from the barrel.  Again, without enough mass in the recoil system I was concerned about the gun beating itself to death.  The first concern is a known issue, but is easy to check.  The second one may just be me worrying about nothing.  IDK.

On the mag tube.  I believe that they had two versions of these guns.  One with a limited magazine capacity.  Maybe called the Sportsman???  Not sure.  But it can't be increased.  The other standard model will accept a standard mag tube extension meant for an 1100.  There's a few pics of those floating around too....

They're neat old guns no matter what you decide to do.  It's yours so just enjoy it.  They aren't exactly rare anyway.

Damn, this is the three-shot model

Is it possible to put a 5 round tube on this gun? I see that Sarco has the tubes...

Most likely you will have issues. Yes, as you stated that is recoil operated. IMO. leave it alone and go get yourself a more modern riot type shotgun if that is the goal.
it might work at 18" but then its to late. I know it will have issues at 14". I had a moron come into the shop with one cut off at 14" looking for us to get it working. I helpped him out by cutting through the middle of the chamber, flattening out the rest with a 3lb hammer and throwing it out.
When i told him the amount of jail time he could expect if caught he claimed he had no idea. He was ok with it. Found him another barrel. he left it alone.

Edit: I should have said. Issues but a good smith should be able to tweek it. Not worth it..IMO.

From what I've read, the barrel length has zero bearing on function UNLESS You go below 15". I'm reading that 15" and up function flawlessly. Dillinger and the like apparently liked "whippet guns" for a reason

You will need to replace the mag tube with the 5 shot version and replace the forend wood so it will not be cheap.The barrel length will not affect function. I love my model 11 but for the cost you would invest in a sportsmen  to do what you want your better off finding a model 11 5 shot.

Tech- what length is your bbl?  My Auto 5 is 20" with a ramped bead.  Who makes your extension and how many is it?

OP: As stated you have a Model 11 Sportsman.  Its up to you but depending on how much you have in it you can convert it and shorten it as you like.the bbl my Auto 5 is 20" and will eat any type/style ammo without missing a beat.  Its really fun to shoot and draws some attention at the range.

Mech- it is 19 1/4 I also have an A5 cut to 20. The model 11 will pretty much eat any ammo I throw at it. The extension I made from parts I got in the white from Choate. You have to use a deeper nut to fully seat the extension against the forend. The 870 extension works but will need a shim underneath. Using 2 3/4 it will fit 7 in the tube.

I thought that looked like a Choate extension.  I would like to add an extension to my A5 but the Nordic is kinda expensive for my taste(more than half what I have in the gun).  Sweet M11 you got there.  Ill post a pic of my A5 when I get home tomorrow.

I've never fired a M11 but I've read several reports that they kicked like the proverbial mule.  I understand the principle of setting the friction rings up correctly, but I've still read reports that even when set up right, they still recoil pretty strongly.  Then I see the one above with the stock butt plate and that makes me wonder...  what is the recoil like with these?  Does cutting the barrel back increase felt recoil?

I didn't notice any difference but I'm in an Auto 5, slightly different from the M11 with its fiber buffer setup.  Never played with a M11.

Yeah, the fiber buffer is the one thing that held up my plans.  My original plan to do a M11 "riot" was when I found a good deal on one with "finish issues".  My initial thought was "no biggie, I'll just Park it."  Then a little more research into the guns lead me to the fiber buffer issue and I realized that the Park solution would probably destroy the buffer even if it was good to begin with.  And unfortunately, replacing the buffer isn't something I can do with common tools....  I knew that the A5 didn't have the buffer but I'm not sure exactly what is different about it that makes it not need one since obviously the Remington does.  I think I've also read that Savage made a similar gun that didn't use a buffer either.  I haven't ran across a project A5 yet and I've never seen one of the Savage models, so the whole idea, while still cool, is on the far back burner for me now.  They're still one of the coolest looking guns in the retro shotgun scene, IMO, though.  

I had an overly buffed and re blued 50's Browning A-5 that I had cut down to 18" and added a Nordic extension.  The shotgun ran like a top and looked awesome but, I found the whole gun pretty abusive recoil wise.  I know my friction rings were set right but, never knew how to check if they were in need of replacement.

You're not the first person that's reported that.  That's another reason I backburnered the idea.  I didn't want to tie up several hundred $$ in a cool looking wallhanger.  And I know that if a gun isn't fun to shoot, that I'd tend to not shoot it enough to justify keeping it.  Of course that's pretty hypocritical of me to say since I have TONS of guns that I don't shoot...  But still, having guns I don't shoot just isn't quite the same thing as buying a gun, then spending time and $$ on the project, knowing up front that I probably won't shoot it enough to justify it...    Too many other guns that I want and at least THINK I'll shoot.  

If it was mine and I wanted a 5 shot with extension, I'd sell it and put the money towards a 5 shot model instead of converting a 3 shot model to a 5 shot.

The Model 11 has a adjustable system for light field loads and heavy buckshot rounds. Anyone that says they kick likely had it set up for light loads and ran buckshot through it.

Dad ran his Savage 16 ga 755a (same gun different look) with the rings set for light or heavy loads even though it had a cuts and never had issues. never had battering either.

Yeah, I'm familiar with the friction ring settings.  I've never shot one personally, so I was just referring to what I've read reported by others.  But, with that said, and as I mentioned above, several of the reports I've read claimed to have the rings set correctly and still said that the guns were unpleasantly hard kickers.  Having no personal experience, I'm just curious since I've read varying reports on this issue...

I've found several missing the steel friction ring. That  means it'll recoil hard with buckshot.

Hmm...well I just took the mag tube apart (stayed on the receiver) and removed a small metal tube that was threaded onto the back of the mag tube cap (front) and it allowed me to fit a third shell into the tube. Seemed to feed pretty well, but I won't know for sure til I shoot it. I'd still like to pick up a 5 shot tube for it....

ETA: I shot this gun the first time with the recoil system set up for light loads and shot some 00 buck through it and holy BALLS it kicked hard. I'm curious to see how it is with the recoil system set up for heavy loads now.

I set mine to heavy and the recoil is not abusive at all. It is one of my favorite guns to shoot and since purchase about a year ago has close to 1,000 rounds through it. The buffer was gone in mine and the rivet was pounded flat in the receiver. A friend is having a machinist make the tools to drill it out and replace it properly. For now I have a new fiber buffer epoxied into the rear of the receiver. The last time I stripped it down the buffer hardly showed any wear on it and was still rock solid in the receiver. Sarco is a great ounce for old factory new parts.

This is mine with heavy game loads at 1350FPS

http://youtu.be/YI9n6xoze3U

The Model 11s are neat guns.

OP, if the gun isn't special to you and you still want to go down the Model 11 path, ditch that Sportsman and pick up a nice 5-shot version.

I found mine on gunbroker a while back, got it for a couple hundred bucks, had Guncat cut it down and add the base/bead. The gun runs perfectly. It was born in 1923 IIRC so no idea how many shells have gone down the pipe in that time, but its probably seen a good 1000 or so in the few years I've had it. The gun never fails! Its a beast, eats everything its fed without issue. Couple things I've come to look for with these things is cracked wood and barrels that are SNed to the receiver.