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Benelli M2 Stock Retaining Nut Screw Issue


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After a couple years of use I finally decided to remove my M2 recoil spring for cleaning. After much research I concluded that the Retaining Nut Screw was possibly attached with Loctite and would require heat to remove. The nut was very tight so I heated it and was able to remove it. I found that there was no Loctite on the threads. There was, however, what appears to be an O-ring (plastic?) at the top of the nut interior threads. On removal of the nut, the O-ring was damaged though not enough to come entirely off the nut. After cleaning the recoil tube and spring, I reinstalled the spring and nut with the damaged ring still in place.


I have a couple of questions about the O-ring and nut. First, does anyone know the purpose of the o-ring? Secondly, is here any potential harm from using the nut with the damaged ring? And, lastly, is there any way of obtaining and replacing the ring only? Otherwise replace with a new nut @ about $20+.


Thanks for any info or advice.

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  • 4 weeks later...

sounds like what is called a "nylock" nut, a type of self locking nut . without seeing it from your explaination. google nylock see if it is the same. get a new one. nylon insert not replaceable. nylon insert locks nut on instead of lock washer, star washer etc. some cheaper self locking nuts are slightly egg shaped if it was still a little tight going on you might be ok. nylocks should turn on and off stiffly not able to turn on by hand

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Photos by permission: Benelli M1 / M2 Anatomy Series of Manuals


For lack of a better term, it is O-ring like. My speculation is that its purpose is twofold: 1) prevent over-tightening of the Action Recoil Spring Retainer into the Action Recoil Tube, not so much when the retainer is fitted to the recoil tube, but rather when the stock bolt nut is being secured- as the shaft is common to both threaded ends 2) function as a soft locking washer. The "O-ring" is not a identified part in the M2 schematic parts list. I have replaced it with a similar-sized O-ring, or if partially damaged (as shown at arrows) ignored it and re-installed it; Regardless of the situation, I do however put a dab of blue loctite so the ramming action of the Action Spring Plunger does not loosen the fitting.



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Your reply is right on and the photo of the damaged "o-ring" looks very similar to mine. You indicated that you have replaced it with a similar o-ring. Did you use a rubber or plastic ring? The original in mine looks like some type of plastic.


Thanks much for you response.

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  • 3 weeks later...

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