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M2 Bolt Return


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With my M2, I've noticed some ammo (like American Eagle) will cycle fine while other ammo (like Fiocchi) will cause the bolt to catch when fully open/driven back in the receiver. I then need to push the charging handle to get the bolt to close/seat again. I recognize that some guns just prefer different ammo. While I can use the 'lighter' ammo, I was wondering what others might recommend to try and tune their M2s to support a broader range of commercial ammo.

 

Some thoughts: Is this a common issue? Is there a recoil spring that works better for hotter ammo (I've tried USGI and Wolff)? Does the hammer spring play into slowing down the bolt? Does the Gen 2 gas piston smooth out recoil from hotter rounds?

 

I'm interested on perspectives for possible approaches to minimize these type of issues - or is it better to just accept the preferred ammo for any given M1/M2 (if it's not broke, don't fix it...)?

 

Thanks for your feedback.

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Could be a short stroking situation- some ammo is under-powered. I reload for my carbine and for whatever reason, Winchester White box works fine in my WIN M2 , but short strokes and fails to feed in my Inland M2. I load the carbine ammo a little hotter - enough to correctly cycle the Inland M2, and it seems to run fine in the WIN M2 and all the M1s . If you could provide more troubleshooting info we could probably narrow it down.

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heavy artillery, on 14 Feb 2021 - 12:00, said:

With my M2, I've noticed some ammo (like American Eagle) will cycle fine while other ammo (like Fiocchi) will cause the bolt to catch when fully open/driven back in the receiver. I then need to push the charging handle to get the bolt to close/seat again. I recognize that some guns just prefer different ammo. While I can use the 'lighter' ammo, I was wondering what others might recommend to try and tune their M2s to support a broader range of commercial ammo.

 

Some thoughts: Is this a common issue? Is there a recoil spring that works better for hotter ammo (I've tried USGI and Wolff)? Does the hammer spring play into slowing down the bolt? Does the Gen 2 gas piston smooth out recoil from hotter rounds?

 

I'm interested on perspectives for possible approaches to minimize these type of issues - or is it better to just accept the preferred ammo for any given M1/M2 (if it's not broke, don't fix it...)?

 

Thanks for your feedback.

So If I understand, when you fire the weapon, the bolt slams all the way back into the rear of the receiver and locks in? You have to push the charging handle in order for the bolt to disengage from the rear of the receiver? When this occurs, have you dropped the magazine to see if the bolt returns back to battery? If this is correct, and magazine not the culprit, would say you need a new spring and guide rod. Also are you firing with a flat bolt or round? If you have a flat bolt firing full auto, could also be a contributing factor. The round bolts weighs more and holds up better to full auto.

 

Jim is right, really need more feedback with what is happening to really diagnose or come up with possible fixes. I have never had this happen to my M2.

Edited by NFA amnesty
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#5 icon_share.pngNFA amnes

 

 

So If I understand, when you fire the weapon, the bolt slams all the way back into the rear of the receiver and locks in? You have to push the charging handle in order for the bolt to disengage from the rear of the receiver? When this occurs, have you dropped the magazine to see if the bolt returns back to battery? If this is correct, and magazine not the culprit, would say you need a new spring and guide rod. Also are you firing with a flat bolt or round? If you have a flat bolt firing full auto, could also be a contributing factor. The round bolts weighs more and holds up better to full auto.

Jim is right, really need more feedback with what is happening to really diagnose or come up with possible fixes. I have never had this happen to my M2.

 

Yes, it locks in and as you described and I have to push the charging handle. The bolt doesn't return when removing the magazine. The fired round has ejected every time. It's a round bolt. I've tried a different spring (that was my initial assumption) but haven't changed the guide rod. I'll try that. I had attributed the issue to hotter factory ammo (or at least it doesn't have this problem when using some ammo).

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My two cents:

 

Check for burrs or peened metal on the bolt and slide. The action on the Carbine is pretty violent, especially the initial impulse from the short-stroke piston and will cause peening where the slide and bolt interact. The pocket in the slide where the lug on the bolt rides is a good place to suspect, as is the little tab on the slide that runs up and down the inletted channel on the outside of the receiver. If you find any raised areas, stone them back down flush with the rest of the surface if you can. They may get battered to the point of needing replacement and then you're stuck spending money.

 

As far as avoidance is concerned, I suggest you use fairly heavy grease in the slide pocket and along the channel on the outside of the receiver, also where the bolt runs back and forth inside the receiver. Use a good strong recoil spring like the Wolff extra-power spring and change it out fairly frequently. Every 3-5,000 rounds would probably be helpful and they're a hell of a lot cheaper than replacing a slide on an M2.

 

FWIW

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Dink may be on to something. It could be the tab on the rear of the slide is engaging in the takedown notch in the receiver.

Could be the tab at the rear of slide is worn or defective and is too sloppy in the receiver track.

Or perhaps the receiver track is worn or defective.

Either condition could allow the rear of the slide to pop up into the takedown notch in the receiver.

If this is the problem grease won't help. A new slide or receiver may be called for.

Jim C

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Check back after you have a chance to look things over. My first M2 was a Plainfield conversion and the steel wasn't the best. I had a lot of battered metal in the areas I mentioned and it took some smoothing out to get things rocking again.

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  • 3 weeks later...

I had observed some looseness when rocking the slide in the track (while cycling/retracted). The slide and track looked fine and I didn't see any peening/damage (so I hadn't really focused on this area). I replaced the slide and repeated the test noting very little wiggle/looseness. I test fired with the new slide and my M2 functioned perfectly. Intermittent issue resolved. Thanks to @DINK and others for the feedback and suggestions.

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