Anjin-san Posted September 16, 2020 Share Posted September 16, 2020 Started new thread because old title not descriptive enough. NIB, unfired M4 is missing mag cap retaining pin and spring. Looking for advice from anyone who has dealt with this problem before. Thanks in advance. Quote Link to comment Share on other sites More sharing options...
StrangerDanger Posted September 17, 2020 Share Posted September 17, 2020 Wish I knew myself. I looked at the assembly and it appears the spring and detent enter from the front of the barrel hanger. It's hard to see what actually retains the detent though. It looks like the area is swaged with some kind of punch or crimp to prevent the detent from coming out. This seems really difficult to do yourself without whatever specialized fixture they have for doing the job. The only way it appears it can work is the barrel is deformed around the edge which stops the detent at the shoulder shown above. Quote Link to comment Share on other sites More sharing options...
Anjin-san Posted September 17, 2020 Author Share Posted September 17, 2020 Thanks for your reply -- Since the parts are readily available from a couple of sources I thought it might be a somewhat common problem, not something that's a factory fix. I'm still waiting to hear from Benelli. Something doesn't smell right about a plastic part like this being so difficult to install or replace. But there is basically no information on the internet about how to install it so I guess if properly installed at the factory, they last forever? One disadvantage to selling the gun disassembled is they will never catch a problem like this before shipping it. Quote Link to comment Share on other sites More sharing options...
bambihunter Posted September 17, 2020 Share Posted September 17, 2020 If it is NIB, can you send it back and get a replacement? Quote Link to comment Share on other sites More sharing options...
Anjin-san Posted September 18, 2020 Author Share Posted September 18, 2020 On 9/17/2020 at 11:21 AM, bambihunter said: If it is NIB, can you send it back and get a replacement? That's the plan now. Requested a return authorization number from Benelli. I don't know how fast they handle repairs like this under normal conditions - much less COVID conditions. My experience with sending guns to other manufacturers for repair: Colt - Terrible, kept gun for 4 months and didn't actually fix it. Uberti - Good, repaired gun in a month or so. Springfield Armory - Great, repaired in weeks. Quote Link to comment Share on other sites More sharing options...
StrangerDanger Posted September 18, 2020 Share Posted September 18, 2020 Benelli is usually 4-6 weeks in my experience. Without whatever fixture they have to swage the detent, it doesn’t seem to be something the end user can fix. Quote Link to comment Share on other sites More sharing options...
Steve Rose Posted September 19, 2020 Share Posted September 19, 2020 On 9/17/2020 at 2:02 AM, StrangerDanger said: Wish I knew myself. I looked at the assembly and it appears the spring and detent enter from the front of the barrel hanger. It's hard to see what actually retains the detent though. It looks like the area is swaged with some kind of punch or crimp to prevent the detent from coming out. This seems really difficult to do yourself without whatever specialized fixture they have for doing the job. The only way it appears it can work is the barrel is deformed around the edge which stops the detent at the shoulder shown above. I bet the 870 detent staking tool would do the job. I think I have one around the shop....somewhere https://www.brownells.com/gunsmith-tools-supplies/shotgun-tools/staking-tools/870-detent-staking-punch-prod25277.aspx An automatic center punch would work in a pinch. A third hand to hold the detest and spring in place while upsetting the metal would help. Quote Link to comment Share on other sites More sharing options...
StrangerDanger Posted September 19, 2020 Share Posted September 19, 2020 11 hours ago, Steve Rose said: I bet the 870 detent staking tool would do the job. I think I have one around the shop....somewhere https://www.brownells.com/gunsmith-tools-supplies/shotgun-tools/staking-tools/870-detent-staking-punch-prod25277.aspx An automatic center punch would work in a pinch. A third hand to hold the detest and spring in place while upsetting the metal would help. Awesome. Order placed. In theory I can see how it works, in practice will probably have a learning curve. Sitting the barrel in a vice so that the barrel hanger At the front is resting on top of the jaws preventing the barrel from shifting downward seems to be the best holding position. 1 Quote Link to comment Share on other sites More sharing options...
Anjin-san Posted September 19, 2020 Author Share Posted September 19, 2020 I'd like to see a close-up picture of a correctly installed detent in that hole. Quote Link to comment Share on other sites More sharing options...
Steve Rose Posted September 19, 2020 Share Posted September 19, 2020 2 hours ago, Anjin-san said: I'd like to see a close-up picture of a correctly installed detent in that hole. This is a M2 barrel Quote Link to comment Share on other sites More sharing options...
Anjin-san Posted September 19, 2020 Author Share Posted September 19, 2020 Interesting - I see what they did. My gun must have skipped this step completely because there is zero indentation or tooling marks around the hole. Its not a case of the hole being stamped wrong and then the part fell out - no attempt was made to close the hole around the detent (if detent and spring were ever installed). Quote Link to comment Share on other sites More sharing options...
StrangerDanger Posted September 19, 2020 Share Posted September 19, 2020 That might be better in your case if you’re going to attempt to stake the parts yourself. Material hasn’t been moved or deformed. Quote Link to comment Share on other sites More sharing options...
benelliwerkes Posted September 22, 2020 Share Posted September 22, 2020 (edited) I haven't installed one nor had sufficient intellectual curiosity just to knock it out for the heck of it BUT if I did this would be my plan. Call factory for replacement support collar; then whack away. But I believe you would have to have the proper support collar for the plunger which I envision as a small externally splined cylinder that allows the spring powered plunger head to traverse thru it. I believe the plunger spring assembly is removed by inserting a 1.5 mm punch thru the access port on the back side of the assembly which would fit thru the spring to greet the back side of the plunger. Installation would be the reverse, probably use a roll pin starter punch ? or a proper sized pin punch to compress the head of the plunger while tapping in what appears to be a support collar that is press fit into the cylindrical recess. Edited September 22, 2020 by benelliwerkes 2 3 Quote Link to comment Share on other sites More sharing options...
StrangerDanger Posted September 23, 2020 Share Posted September 23, 2020 Awesome info Benelliwerks! Quote Link to comment Share on other sites More sharing options...
Evolution Posted September 23, 2020 Share Posted September 23, 2020 Yeah BW, excellent job of reverse engineering. Quote Link to comment Share on other sites More sharing options...
Anjin-san Posted September 23, 2020 Author Share Posted September 23, 2020 Fantastic analysis - A masters class on the mag cap retainer assembly. I can clearly see the assembly sleeve has to be a different factory-only part. That could not be formed only by deforming the metal around the hole. I am sending it back to Benelli (the customer support I talked to was outstanding). It will be interesting to see if they attempt to put in the spring and detent or just swap the whole barrel assembly. One thing still bothering me is why sell the detent and spring replacement parts and not the sleeve? Nobody is going to be able to swap a worn or broken detent or spring without a new sleeve unless they can fabricate one or remove and replace the sleeve without damaging it... Quote Link to comment Share on other sites More sharing options...
benelliwerkes Posted September 23, 2020 Share Posted September 23, 2020 ^^I have never asked the factory parts guys if there is a part # to purchase. Quote Link to comment Share on other sites More sharing options...
Steve Rose Posted September 24, 2020 Share Posted September 24, 2020 On the Brownells schematic and parts # listing the cap retaining pin and spring are the same on the M2, M4 and Super Black Eagle. No mention of a “sleeve” (I still think the retaining pin is staked in place) 1 Quote Link to comment Share on other sites More sharing options...
Vertigofirearms Posted September 24, 2020 Share Posted September 24, 2020 45 minutes ago, Steve Rose said: On the Brownells schematic and parts # listing the cap retaining pin and spring are the same on the M2, M4 and Super Black Eagle. No mention of a “sleeve” (I still think the retaining pin is staked in place) I concur. Quote Link to comment Share on other sites More sharing options...
StrangerDanger Posted September 24, 2020 Share Posted September 24, 2020 Agreed. It appears you’re deforming the steel of the barrel hanger to put a lip on the retaining hole. So the barrel is probably only good for so many swage events. Brownells delivered the tool for staking these today. Looks like a solid tool. Hope I never use it! 1 Quote Link to comment Share on other sites More sharing options...
benelliwerkes Posted September 25, 2020 Share Posted September 25, 2020 SD - What tool do you speak of ? Quote Link to comment Share on other sites More sharing options...
StrangerDanger Posted September 25, 2020 Share Posted September 25, 2020 3 hours ago, benelliwerkes said: SD - What tool do you speak of ? The one Steve Rose linked up near the beginning for the Remington 870. It should work for the Benelli. Quote Link to comment Share on other sites More sharing options...
benelliwerkes Posted September 26, 2020 Share Posted September 26, 2020 ^^Got it. Thanks. Quote Link to comment Share on other sites More sharing options...
benelliwerkes Posted October 4, 2020 Share Posted October 4, 2020 The Remington 870 staking punch should work just fine. 2 Quote Link to comment Share on other sites More sharing options...
Anjin-san Posted October 9, 2020 Author Share Posted October 9, 2020 That was fast! Its back after being fixed by Benelli. Invoice shows pin and spring installed and then test fired with no malfunction. 2 Quote Link to comment Share on other sites More sharing options...
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