How to Install a Magazine Extension on Benelli M4

How to Install a Magazine Extension on Benelli M4 and How I installed the Dave’s Metal Works add on two piece magazine extension on my Benelli M4.

Now after learning more about 922R I understand that installing the extension is not the best way to add the extended magazine. The best method is to install the full length US made magazine tube, US made magazine follower, and US made fore end. Adding these US made parts makes the M4 922R compliant.

Since installing the magazine extension I have learned more. Click here to learn how to Keep your Benelli M4 legal and in 922R compliance.

1. First make sure gun is safe, check magazine, cycle bolt to check chamber.
The red magazine follower indicates an empty magazine.
Cycle the bolt to see that the chamber is empty. Verify the empty chamber.
2. There are several choices in magazine extensions:

  • Full length
  • Add on, two piece extension
  • Steel
  • Titanium

3. Suppliers and Manufacturers include:

  • Daves Metal Works -Add on two piece, and Full length magazine tube
  • Pro Mag
  • TacStar
  • CarrierComp – Titanium
  • Freedom Fighter Tactical – Titanium
  • Brownells
  • MidwayUSA
  • – Benelli Add on extension

4. To install the magazine extension
Note the Benelli spacer installed in lieu of the magazine extension.
Caution: The magazine spring is under considerable compression.
Caution, wear eye protection
Remove the barrel nut
Remove barrel
Remove split retainer
Caution: Spring is compressed.
Remove the spring seal washer – The spring will fly out at some point
Remove factory spring
Unscrew and remove the Benelli spacer
Screw on the new add on magazine extension
Install new longer spring
Install spring seal washer
Install spring split retainer
Install the barrel
Install the fore end pieces. They are marked LEFT and RIGHT.
The front of the plastic fore end grip goes in first
Install the barrel nut
Finished – The Benelli M4 now has a 7 round magazine capacity.

How To Install the Full Length Magazine Tube.
Disclaimer: The following information is not a recommendation to install a full length magazine tube on your Benelli M4. It is provided so one can compare the complexity of installing the full length tube compared to the ease of installing the add on extension. In fact, I recommend using the add on extension. I installed the Dave’s Metal Works extension and I am very pleased with the appearance, the ease of installation, and the performance. With that said, many have installed the full length tube with good results.
Benelli uses LocTite when they install the factory magazine tube.
Installation of the one piece tube requires heating the receiver to about 300F to loosen the LocTite.

  • Remove the barrel
  • Remove the magazine spring and follower
  • Strip the receiver –  Remove the bolt, Remove the trigger group, remove the pistol grip and stock.
  • Use a heat gun, do not use an open flame as it may discolor the finish.
  • Wear oven mitts.
  • Apply heat to the receiver.
  • Do not apply heat to the magazine tube.
  • When the receiver reaches 250F to 300F the factory tube can be turned.
  • Using oven mitts, unscrew the factory tube.
  • NOTE: Don’t forget the metal bracket that holds the fore end grips
  • Install the new full length magazine tube with fore end bracket while the receiver is still hot.
  • No need to use LocTite
  • Using oven mitts screw the full length tube into the receiver hand tight
  • The heated receiver will shrink down on the new magazine tube and some residual LocTite will provide tight fit.
  • Let the receiver cool
  • Reassemble the gun

NOTE: I decided against using the full length magazine tube because I didn’t want to apply heat to the receiver of my new $1,600.00 shotgun. The add on two piece Dave’s Metal Works magazine extension that I installed works fine, was easy to install, and I am very pleased with it. I highly recommend using the add on two piece extension.
Video Install Magazine Extension on Benelli M4

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