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Benelli M4 -- Magazine Tube Polishing


StrangerDanger
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I figured I'd share this basic gunsmithing technique to enhance reliability in pretty much any shotgun that is fed from a magazine tube. Generally, I avoid doing this technique on steel magazine tubes since it can remove the protective finish and you may face rusting issues depending on your climate.

 

Magazine tubes like the titanium tubes from carriercomp and FFT benefit from this the most. Titanium tends to gall against other metal surfaces. This can diminish the strength of the shell delivery system. For an example, insert one shell into your magazine tube. Now, use the shell release to eject a shell onto the elevator. Listen to how it sounds, how it feels, and how far back the shell it ejected onto the elevator. Compare this to how it feels when your magazine tube is full and under full spring tension.

 

Another issue that is commonly misunderstood about the magazine tube is you do not want any kind of lubricant whatsoever inside of it. If you have a steel tube that is prone to rusting, you may apply a surface coating of a rust inhibitor. Lubricant breeds an environment for debris to be present inside the magazine tube. This can turn into a sticky situation that will slow down the shell delivery system.

 

How many times have you heard people claim the weapon works great until the last shell in the magazine tube? These are signs that one of the following problems exists;

1. The magazine tube is dirty

2. The magazine spring is incorrect or worn out

3. Friction inside of the magazine tube is retarding the shell delivery

4. The magazine tube or follower is bent or damaged

 

To really squeeze the very best performance out of your magazine tube, you'll need to polish the full length of the magazine tube. When you look inside you tube, it looks and feels to be pretty smooth. Take a look at my three or four year old carriercomp titanium magazine tube.

 

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Notice the oxidation and dull looking finish? These imperfections drag on the spring, the follower and even the shells as they slide down the magazine tube towards the shell stop. We intend to fix this and test exactly what kind of end user improvements are felt.

 

To do this job correctly, you need to remove the magazine tube from the weapon. Without doing so, you'll be making a huge mess that will be difficult to clean up. You'll be stuck using a longer length of rod to do the internal polishing as well. It isn't going to work well. Having a vice is pretty much mandatory. The tube will be getting hot and it will be difficult to hold the tube still while you're performing the high speed polishing. A padded vice is ideal, but you can get by with some shop rags. Do not crush the tube to the point that you cause damage.

 

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You need the following shop materials to perform this task. I purchased some 0000 steel wool from Walmart for about three bucks.

 

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You are going to need some polishing paste. I purchased this from Brownells a while back. I have three different grits. The 600, 800 and 1000 grit.

 

You are going to need an electric drill gun, a section of cleaning rod at least 10 inches long that you can put in the drill chuck. A 12 gauge brush that fits the cleaning rod as well. Recommend eye protection as well.

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Now, this isn't rocket science, so I don't feel I need to show every step of the way. Put your cleaning rod in the drill chuck with the brush installed. Now cut sections of the steel wool and wrap it around the brush. You want enough on the end of the brush so that it presses tightly into the magazine tube.

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Smear some of the lowest grip polishing media you have onto the steel wool or into the end of the magazine tube. Push the steel wool brush assembly into the magazine tube. Start out slow to make sure you can get the hang of the vibration caused by the unevenly wrapped steel wool. You may wish to wrap the threaded end of the magazine tube with painters tape if you're concerned about accidentally making contact.

 

I ran my drill on high for about 10 minutes on each side of the magazine tube. I then wiped the tube out, threw away the steel wool, re-wrapped it and moved up to the 800 grit paste. I followed this same routine through the 1000 grit paste as well.

 

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Once this was complete, I wiped the tube out thoroughly with hot soapy water to remove any paste left behind. The inside of the magazine tube is nearly a mirror finish from top to bottom. Feeling with your finger, you can tell the definite improvement in surface smoothness.

 

Upon re-installation of the weapon, there was an immediate difference in feeling when ejecting the shells onto the elevator. You actually feel the weapon kick back with authority from the last shell in the magazine tube. The magazine tube still has that raspy spring scratching noise when loading shells. Shell loading is improved a minor amount. You can feel that they are easier to press in. Overall, I found it to be a worth while technique to improve weapon reliability.

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Good idea to polish the tube, but you may want to use something other than steel wool as the abrasive. Steel wool will imbed itself in many metals and rust even if used on a non rusting surface (like aluminum). I polished some aluminum, stainless steel and titanium parts on my dirt bike using steel wool and all showed rust within six months.

 

Using a high #automotive sandpaper (1000-2000) in sequence will give good results, followed by Flitz or Semichrome polish. Also dry teflon will reduce friction and not attract dirt or grit.

Edited by paochow
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My concern with those polishing bits is they are pretty low grit levels. 180 grit is pretty rough stuff. Plus, you'd have a hard time getting into the center of the magazine tube. You'd need to rig up some sort of extension/chuck.

 

Brownell's had some polishing brushes that looked like this, but they are pretty expensive and I'm not sure if the diameter would be exactly what you need.

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You could fill it with your abrasives, and other suitable media - think like a stuff to polish rocks or brass - tape up the ends - then either vibrate it to death by securing it to something that will continuously vibrate vigorously. Or if you can rig up something to tumble it on axis. I think either would work.

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Both Titanium and aluminum are highly suseptable to galling, the combination of an aluminum follower in a Ti tube, I suspect will eventually result in scrubbing of the naturally forming protective oxide layer and galling will result.

Just FYI , here is a pix of the inside of one of my chrome -moly steel tubes... nice shiny finish on the drawn (DOM) tube.... no galling here!

Edited by SOCOMguy
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  • 2 weeks later...
You could fill it with your abrasives, and other suitable media - think like a stuff to polish rocks or brass - tape up the ends - then either vibrate it to death by securing it to something that will continuously vibrate vigorously. Or if you can rig up something to tumble it on axis. I think either would work.

 

http://www.youtube.com/watch?v=xXHUdvvHTkw

 

Surely some lucky lady you know would be willing to help you?

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Both Titanium and aluminum are highly suseptable to galling, the combination of an aluminum follower in a Ti tube, I suspect will eventually result in scrubbing of the naturally forming protective oxide layer and galling will result.

 

What about a Ti tube with a stainless steel follower?

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