I’ll post pictures later, if desired.  

I “think” I got a good deal on a used 1301 Comp.  Out the door for $920 ($70 in taxes).   It’s the 21 inch barrel.  

However it’s not without some issues.  

1.  The front sight is loose.  I can try some loctite or replace it completely.   If I replace it, I’d like to go brighter.   Which one?

2.  The magazine tube is aftermarket and is a foot longer than the barrel.  It’s also damaged from the blast, appears to be carbon fiber.  

Which tube should I get and where to get it from?

This is what I need to do first.  

3.  The fore end is kinda mangled, but I can restore it.   If I can’t, I’ll replace it with Magpul stock and fore end, I assume the fore end will fit the 1301 comp?   Is that correct?

Interesting.   Now it makes sense.  The counter guy said, don’t let the range officer see you with this extension.    I totally assumed he said it because it looks absolutely ridiculous and its taking blast damage.   Never thought about 922 (which is also crap).  

Ok!   I’ll go all Magpul on the furniture, where should I get a compatible magazine tube?

Edit.  Just took off the offending tube.

My 21" Comp has a Lancer CF mag tube on it, which brings the tube out even with the barrel (+2 or +3, iirc).

Just saw this. Your front sight is held on by a nut, it uses an 3mm wrench and tighten it back down, a dab of blue or red loctite will help. If you want to replace it with a new one you can find it at MWG. https://www.midwestgunworks.com/page/mgwi/prod/C55674

Another option is the tritium FO Hi viz sight. It comes with various nuts to fit various shotguns. The 1301 uses the 3mm. This would be a huge improvement over the standard FO sight.
https://www.midwestgunworks.com/page/mgwi/prod/pmn301

The Magpul furniture is a step up over the standard. Aridus just came out with their V2 version of the Zhukov handguard. They have a better mount set up for it and now offer laser texturing. This handguard will give you a lot of options for match savers, sling and light points. Pricy but one of the best upgrades for the 1301 IMO.
https://www.aridusindustries.com/products/1301hga-blk/

For a magazine tube, I like Nordic or Toni Systems. For your gun you want a +3 set up.
Toni

Unfortunately Nordic doesn’t sell the extension as a lot for the Comp model like they do for the Tac version. So you’ll need to buy the extension nut and tube kit.

This may still extend out past the barrel slightly the idea is that the tube will be flush with an extended choke.
Tube kit, at least a +3
Nordic MXT extension nut.

Out of the two the Nordic is the tougher tube. The Toni is lighter and geared towards competition.

They give you a chart with the measurement of each tube's length, which is handy.

Lancer Carbon Fiber

Alright, got a plan.

I bought a stock and fore end off of EE.  It’s on the way.

Now it’s time for a replacement tube.  Matthew from Lancer System wrote back and told me how to size the tube.

From the base of the threads to the end of the barrel is 10.5 inches.  

If I go with
+4, it adds 11.5 inches
+3, it adds 8.9 inches
+2 it adds 6.3 inches

I am thinking +3 at 8.9 or even +2 at 6.3.  I am wondering about a fully loaded magazine and the weight that far out.  Thoughts on that?

Edit.  The tube that came with the shotgun is a +7 at 19.4 inches, or 9 inches past the end of the barrel.