Benelli M4 -- Receiver Extension Servicable?

[StrangerDanger]

On my older M4 11703 hybrid shotgun, I've determined part of my cycling speed issues has been caused by the spring in the receiver extension.

 

We just got a second M4 11707 last week. The actions are significantly different in stiffness. Even after oiling and feeding several hundred rounds though the new M4 the past few days. When cycling the same type of shells, you can feel and hear that the newer shotgun is cycling faster. I cannot make the newer one jam due to beating the trigger disconnector.

 

11,000 - 12,000 rounds seems to have taken it's tole on the mainspring.

 

I don't want to hit the receiver with a flame to take the receiver extension off. Can the spring and plunger set be removed from the extension at the rear of the extension? There is a snap ring present, but I've been unable to locate tech data on the procedure.

 

I don't want to tear it apart for no reason.

Thanks

[StrangerDanger]

I figured what the heck and tore it apart. It's actually rather easy to disassemble the recoil extension. The only thing that is a pain is taking the extension off of the receiver.

 

ftp://ftp.benelli.it/Public/UM_SPL/G0227900.PDF

Pages 12 and 13 have a parts diagram and referenced names.

 

1. Unscrew the stock or slide off the collapsible stock.

2. Use a pair of snap ring plyers and remove the snap ring from the base of the receiver extension. This is the portion that screws into the stock or indexes with the collapsible stock portion.

3. There are two witness holes on the bottom side of the receiver extension. Insert a punch through one of the holes in order to prevent the spring from shooting out.

4. Unscrew the stock retainer screw from the end of the receiver extension. This has a strange castle nut style head. A very large flat head would work. My snap ring plyers worked also. It isn't torqued down. The spring is being held captive by this part. So be careful as you unscrew it all the way.

 

5. Put your thumb over the end of the receiver extension as you remove the punches.

 

6. The spring will simply pull out and the recoil spring plunger will just slide out after it.

 

Done.

 

There was a metric ton of crap inside mine. I blasted out the inside of the tube with Breakfree Powder blast. It looked like coffee pouring out for about 20 seconds.

 

I forgot that I had accidentally bought a action spring a year ago thinking it was a replacement magazine tube spring. I wasn't a 100% sure that it was for the receiver extension. I believe the one I put in was from Wolff.

 

Reassembly is easy. Lightly lubricate the parts. Push the recoil spring plunger back into the receiver extension. Then insert the spring. Press the spring in as much as possible by hand, and push the punch through the witness holes to capture the spring in place. Finish pressing the spring in with the stock retainer screw and begin screwing it in. Once it is in, remove the punch from the witness hole. Reinsert the snap ring into the end of the receiver extension.

 

Done!

 

I'm going to add this to my cleaning process after 2,500 - 3,000 rounds being fired. I've tried flushing this area out in the past with breakfree, but it doesn't seem to have gotten all the debris out.

 

I need to go test fire some rounds later this week, but the action now feels identical to my brand new M4. I never noticed how much the M4's action had weakened over time since it was a gradual decline. Only when compared with a new M4 was it obvious. So if you've got a lot of rounds down the pipe, you might want to consider a new spring. Perhaps every 5,000 rounds would be a good idea. It is not just "broken in more".

 

I sent an e-mail to Wolff asking if their springs will fit the M1014 series.

http://www.gunsprings.com/index.cfm?page=items&cID=2&mID=10#468

Edited December 31, 2009 by StrangerDanger

[Unobtanium]

On my older M4 11703 hybrid shotgun, I've determined part of my cycling speed issues has been caused by the spring in the receiver extension.

 

We just got a second M4 11707 last week. The actions are significantly different in stiffness. Even after oiling and feeding several hundred rounds though the new M4 the past few days. When cycling the same type of shells, you can feel and hear that the newer shotgun is cycling faster. I cannot make the newer one jam due to beating the trigger disconnector.

 

11,000 - 12,000 rounds seems to have taken it's tole on the mainspring.

 

I don't want to hit the receiver with a flame to take the receiver extension off. Can the spring and plunger set be removed from the extension at the rear of the extension? There is a snap ring present, but I've been unable to locate tech data on the procedure.

 

I don't want to tear it apart for no reason.

Thanks

 

Remove snap-ring, un-screw threaded plug. Should be as simple as that, I hope Benelli did not use an adhesive on that plug, but I doubt it as they put a snap-ring in there. Redundancy yes, double-redundancy? Less likely.

[cody6.0]

Remove snap-ring, un-screw threaded plug. Should be as simple as that, I hope Benelli did not use an adhesive on that plug, but I doubt it as they put a snap-ring in there. Redundancy yes, double-redundancy? Less likely.

 

The SuperNovas with the PG stock used the notched tube similar to the one on M4's and also used the same snap ring and threaded plug. Neither of mine had threadlocker so hopefully the same applies to M4's.

[StrangerDanger]

No thread locker was present on mine.