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MP-40 barrel nut torque


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If you are looking for an actual torque setting there isn’t one since each gun’s parts fit together differently. Tightness should be sufficient to keep it from loosening when shooting. Some MP40s that I’ve had in the shop had the nut tightened enough so that I had to make a couple special tools and special clamp to hold the receiver, use heat and oil to get the nut off. The receivers of these guns can take a lot of torque without twisting and deforming, but most owners anchor the receiver to unscrew the nut by torqueing against the magwell. The magwell is pinned onto the tube with one pin and if used as a counter to unscrewing the nut, the pin holes will enlarge and the magwell become loose. Torquing against the front sling loop can deform the loop.

So, if you have a safe way of anchoring the receiver, tighten the nut snuggly and see if it loosens up. If it does, clean the threads of the nut and the receiver and use a drop or two of loctite and snug it up again to where it was before. Hope this helps.

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  • 1 year later...

Here's a pic of the factory installed staked locking ring on my '41 bnz MP-40. The barrel nut has never been removed. Have no idea what torque value was originally used, but it shows no sign of loosening on its own after 78 years. The sling ring wiggles slightly.

MVC-093S.JPG

Edited by TSMGguy
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Thank you TSMGguy. I have tightened the nut as best as I can, but it likes to get loose. I bought a NOS ring and will try that. Now, I may have to go look, buy my sling ring may be facing the wrong way! If that's the case. It came that way when I bought it 10 years ago!!

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I suspect the stakes in the locking ring prevent self loosening of the nut.

 

Right, the sling loop was factory installed on the right side where the sling doesn't foul the operating handle or get in the way of switching magazines. I'm a leftie, so the sling is always in my face!

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