Benelli M4 -- Receiver Extension Removal/Reinstallation Guide

[StrangerDanger]

 

 

[benelliwerkes]

Stranger.

 

Nice neat photos and a clean work bench.

 

The receiver lock nut is a 27 mm for those that have that size.

 

After cleaning off any debris as you described and before you apply the heat, they can also use a silver sharpie to index mark the tube to the receiver as well as count exposed threads rearward to the locknut for reference when re-assembling.

Edited January 9, 2013 by benelliwerkes

[BigHat]

Damn! You do a really nice job on these. Worthy of a sticky. Not planning on doing this anytime soon, but this will be helpful to those that opt to disassemble to this level.

 

Thanks for the effort and thanks for sharing.

[jaggedx]

I agree with BigHat. I feel smarter just from reading this thread. Nice work!

[StrangerDanger]

Thanks! I'll be editing some of the text over the next day or so to make it a little clearer. By the time I got to copying the text into these boxes, I was pretty tired of doing it.

 

Pretty much the only reason to ever disassemble one of these extensions is if you have an older model M4 that you want to add a three position receiver extension to. Pulling the components out of the receiver extension should be done if the weapon is ever submerged or after 2500 rounds or so.

 

Having a clean work area helps a lot. I have two 7' x 3' tables set so there is one in front and behind me. A vice mounted to one and a reloading press mounted to the other. Both have a large rubber mat on them to reduce scuffing and marring.

[dannymac63]

Stranger, as I wrote in my PM, I don't know how to thank you enough, I was thinking a range session and a cold one after on me, but it doesn't even seem worthy.

[StrangerDanger]

If we were closer, I'd help you do the install. I've wanted to do this write up for a few years now. Just finally got motivated enough to actually do it.

[paladinjme]

Great job SD...I've referred several people to your previous posts about this process, but this one is even better!!! Thanks.

 

..I noticed you didn't get into part #183J ...the dreaded 'flexible ring'... I have some 'tips' for removal, but it takes some explaning and pics to make clear, I may try to put that together to 'compliment' your already great thread..

Edited January 11, 2013 by paladinjme

[StrangerDanger]

Please do! I was never able to remove that ring myself. I tried with two sets of picks until I gave up. I've put several in, that is easy. Getting them out is a pain. I just assume buy a new one.

 

So people know what we're talking about, this is the Flexible Ring. It is what keeps the Recoil Spring Plunger from pushing through into the receiver.

 

With and without the Flexible Spring installed

[StrangerDanger]

Alright, I finally found a surefire way on how to get the Flexible Ring out of your existing extensions. After removing the Receiver Extension from the receiver, put the Receiver Extension in a vice with the Flexible Ring side up. I've tried for nearly an hour to dig the Flexible Ring out with various tools. It's impossible and you'll just break tools that cost more than the five-dollar part. Sadly, these little rings are hard to find and are usually out of stock.

 

The best solution is to modify your Receiver Extension by cutting a small notch into the lip of the Receiver Extension. This will allow you to hammer a small punch or blunt tip probe behind the leading edge of the Flexible Ring. With this mechanical leverage, you can easily dislodge the Flexible Ring and recover it.

 

To make the notch, I just used a small cut off wheel and a Dremel tool. Note where the Flexible Ring is, and cut in the gap between the open ends of the Flexible Ring. Once the notch is complete, simply use a probe or punch to slide the Flexible Ring over the notch. The Flexible Ring freely spins within its race. The notch will not affect function of the Receiver Extension whatsoever. Besides, you're not using that extension anymore and they pretty much have absolutely no resale value.

 

Naturally, I took some pictures of the process.

 

Here the notch was cut with a Dremel cut off wheel. You don't need to go too deep, just enough to allow your probe to get under the back side of the Flexible Ring. The notch is shown in red, and the open ends of the Flexible Ring are shown in green. Hope you guys aren't color blind!

 

Do not try to cut your notch on top of the Flexible Ring. You'll damage it in the process. Cut the notch between the open ends of the Flexible Ring.

 

 

With a probe or a punch, push on the edge of the Flexible Ring. The Flexible Ring will spin freely within the race. Align the leading edge of the Flexible Ring over your newly cut notch.

Edited February 7, 2013 by StrangerDanger

[StrangerDanger]

Once the notch is cut, it is easy to remove the Flexible Ring. I tapped on my probe with an 8 ounce hammer very lightly. This cause the probe to push under the end of the Flexible Ring and dislodge it from the race.

 

Continue to drive it downward until the entire Flexible Ring has dislodged from the race.

Edited February 7, 2013 by StrangerDanger

[StrangerDanger]

Once the Flexible Ring is dislodged, hook the loop with a punch or a probe and pry it out. Be careful, this part is under spring tension and tends to fly.

 

For such a small part, it is a troublesome one to get out.

Edited February 7, 2013 by StrangerDanger

[StrangerDanger]

Press the Flexible Ring into the end of the Receiver Extension. As you press it in, you will be compressing the ring so that it can pass into its race. Pressing the Flexible ring in with a punch is the easiest method I've found. Once in, pry upward on the Flexible ring until it seats in place.

 

Be sure that all the edges of the Flexible Ring are recessed into its race.

 

With the capacity to disassemble the Receiver Extension completely, you can buy a stripped 3 Position Receiver Extension and transfer all your existing internal components over from your existing unit. This will save you some time and money.

Edited February 7, 2013 by StrangerDanger

[benelliwerkes]

SD

Here are some tools that can be easily fabricated that I have used to remove the flexible rings.

 

[benelliwerkes]

Continued.........

 

Edited February 7, 2013 by benelliwerkes

[StrangerDanger]

You have some great tools beneliwerks. I tried several hooks to dig out the Flexible Ring, but failed. I figured I was just going to break my hooks.

[benelliwerkes]

SD,

 

I contacted this company today.....Retaining Ring Pliers - Specialty Products & Services | RingMasters LLC.....

they even specialize in custom ring pliers !!!! no luck for the style used on the Benelli.....that's why I have resorted to some of these Flinstone looking fabrications.......still searching though.

[benelliwerkes]

Although the installation of the flexible ring is much easier than extraction, the installation task can be performed in a more controlled manner by using a simple hose clamp and compressing the ring slightly smaller than the internal diameter of the receiver extension and then pressing it out of the clamp into position.

 

 

Edited February 8, 2013 by benelliwerkes

[benelliwerkes]

Continued......some might find it useful that the same principle can be applied when trying to install a tight magazine retaining cap that does NOT have holes that could be compressed with internal snap ring pliers.....this illustration just happens to have a retainer with holes. This trick often prevents the marring of parts that is the goal when manipulating the gun art.

 

Edited February 8, 2013 by benelliwerkes

[StrangerDanger]

Benelliwerkes,

That first tool looks like it would work best. Along with slipping that piano wire hook under the raised edge.

 

Milling a notch into the slot works very well. Sometimes it sucks to modify a part to work on it. In this case, the modification doesn't effect function or even looks really. You'd be hard pressed to even see it. Notching the extension took about 15 seconds and will make future service a breeze. Benelli would probably install such a cut if it wouldn't create another milling operation for them to price out.

 

If re-installing in the modified extension, you just put the gap between the Flexible Ring over the notch.

 

Pretty smart to use the hose clamp to compress the ring. With this extension, it is pretty easy to just push the ring into position. I could have used the hose clamp idea on a Magazine Spring Retainer I encountered a while back. Nearly broke the snap ring pliers trying to compress it enough.

[paladinjme]

My approach for removing the flexible ring was similar StrangerDanger's although I just used 5/32 or so drill bit to drill a small 'indentation' in the race that the ring rides in that is slightly wider than the race itself, then rotated the ring so that you can insert an awl or similar sharp pointed device into the indentation beside the ring, push it under the ring and pry it out. Hopefully, you can see from the pic that the 'indentation' is inconsequential and almost not even noticeable.

[ATTACH=CONFIG]1923[/ATTACH][ATTACH=CONFIG]1924[/ATTACH]

Edited February 8, 2013 by paladinjme

[StrangerDanger]

Great minds think alike!

[benelliwerkes]

.......... I encountered a while back. Nearly broke the snap ring pliers trying to compress it enough.

Those stamped sheet metal magazine retainers can be surprisingly STIFF.....and like you said, trying to reduce the circumference of the retainer with application of force to those existing small holes with snap ring pliers, often times, will deform or tear thru the hole in the retainer......leaving you with a screwed up part that still isn't installed ! Been there.

[StrangerDanger]

Had a brand new 11707 M4 kick my ass today. I roasted the receiver extension for 2 and a half hours with my heat gun. Didn't budge a millimeter. The lock nut wouldn't even break free. I think Benelli is using a different type of locktite now. I'm probably going to have to double down and get a better heat gun that can reach a higher temp.

 

Even the magazine tube was held on by a different type of locktite. The new thread locker is a reddish color.

[benelliwerkes]

As I'm sure you know the red Loctite requires ~ 500 deg F to be degraded. A heat gun rated at 1,000 degrees and, just as useful, is an infrared digital temperature gauge to know when the parts are hot enough to attempt disassembly; often times we use the "smoking" sign to start rotating the parts apart, but sometimes the smoke may appear when the temperature on the loctite may still be 100 deg or more from breaking down. The IR temp gauge let's me know when to start using muscle efficiently to proceed with disassembly. Just because the heat gun is "rated" at a specific temperature does not mean it can get the parts that hot. Finally, for those that are attempting to remove loctited parts, make sure you remove the trigger guard, magazine spring and follower, etc. as they will act as heat sinks making the task even more challenging, not to mention, ruining some parts.

 

Edited April 17, 2013 by benelliwerkes