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Strange M50 Bolt Failure


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#1 DGinGA

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Posted 15 May 2019 - 04:12 PM

Today I went to test some reloaded ammo in my M50: 185 gr round nose, 6 gr of 231. Hornady data says abt 800 FPS. Fired 3 rounds, no extraction. After hat, the operating rod wouldnt push back the bolt. The lower read of the bolt underside had broken off. Id may have expected that with hot loads; is there any reason light loads could cause this? Ive read about Reisings can have interchangeability issues - will fitting be needed for another bolt?
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#2 ron_brock

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Posted 15 May 2019 - 04:52 PM

See this series of threads. I cannot quite tell from your text and some auto correct, did the bottom rear of your bolt break off?

http://www.machinegu...opic=19926&st=0

Ron
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#3 dalbert

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Posted 15 May 2019 - 08:38 PM

Yes, a new bolt will almost certainly require fitting, and it sounds like your issue aligns with the failure most commonly encountered.  This was the genesis of the reputational issues for the Reising at Guadalcanal, when parts were switched during communal cleaning.  The Reising was never required by the USMC to have interchangeable parts because the USMC wanted the weapon on an expedited basis, because they couldn't get Thompsons, so they agreed with H&R to supply hand fitted Reisings, which was H&R's normal process.  The USMC just did not communicate this well internally...thus the bad reputation coming out of the first action in the Pacific.

 

David Albert

dalbert@sturmgewehr.com


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#4 DGinGA

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Posted 15 May 2019 - 09:52 PM

Should proof posts before posting. Sorry about the errors. The underside of the bolt has a milled angled cut, into which the operating rod end fits. A portion about 5/8” broke off, so with nothing to push against, the operating rod can be moved back, but the bolt stays in place. I’ve had this gun for a year or so and fired about 550 rounds. Seems odd for this failure to happen now.
How is a part ‘fitted’? How would I know if the bolt doesn’t fit properly? Are there gunsmiths who do this?
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#5 emmagee1917

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Posted 16 May 2019 - 11:36 AM

This is not surprising at all . I've used W231 for decades using 5.3gr behind a 230 gr FMJ . After getting into lightweight Commanders and Defenders , I've dropped to 185 gr under the same charge . Looking in the online Winchester load data the min / max of W231 in 45acp with 185gr is 5.0/5.9 . Loading over max is not a light load and that area of the bolt is the place that gives under high preasure .

 

The bolt lifts up into a locking notch . It has to headspace and lock up at the same time . If it doesn't it will either not fire at all ( the hole in the hammer is to keep it from hitting the firing pin if the bolt does not tilt up ) , fire when only partly locked up ( upper bolt wear and / or reciever damage in the lockin slot  ) to beating itself to death ( excessive headspace ) .

 

Chris


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#6 BillyDixon

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Posted 16 May 2019 - 04:20 PM

years ago i bought several reising m-50s from a highway patrol office, when we took apart to clean them the bolt was broke as you describe and the broke off part fell out. then once i bought a  bag of resing parts and there was a bolt broke as you describe in the bag, just sayn


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#7 StrangeRanger

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Posted 16 May 2019 - 08:53 PM

Every piece of steel in a machine (or machine gun) which is subjected to cyclic loading has a fatigue life.  The greater the loading, the fewer cycles the part can withstand before failure.  Reisings are getting old and many have seen a lot of cycles.  Unlike TSMGs they are not over-engineered to the point of near indestructibility.  Add to that the fact that the design of the bolt creates a stress concentration at the rear of the cutout which further reduces the expected life and no failures in that area should be surprising.


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#8 DGinGA

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Posted 16 May 2019 - 09:37 PM

I found another bolt. It fit, but the action was tighter than usual. Before firing, I polished the bolt with 400, 600,800,1000,1200,1500,2000 grit sandpaper and assembled. BTW, I was mistaken about my load recipe: should be 5.0 gr 231. Quite pleasant out of my AMT long slide; little recoil or muzzle flip. In the Reising, in semi, got failure to cycle every other round. Never went FA at all. Fired Remington 185 gr, 1045 FPS; gun worked perfectly, fired fast and climbed. My 230 gr 850fps was better. Going to a sub gun shoot this weekend, but think my S & W 76 will be used the most. Aftermarket barrels are readily available, and simply screw in. I’d even shoot steel case ammo. StrangeRanger’s observation about the Reising age and fragile design are correct. So I’ll use the 76, and my new/old Stemple 45/9mm for heavy use. The M50 won’t be a total safe queen; a few hundred rounds per year only.
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#9 StrangeRanger

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Posted 17 May 2019 - 08:39 AM

FWIW all steels are not created equal.  If anyone is considering making their own Reising bolts (and yes I have considered doing it), the selection of material is critical.  I have no idea what the originals were made from but looking at the data I have available I'd be torn between a specially heat treated version of 1144 steel commonly trade named "Fatigue Proof" or a heat treated version of 4130 which has very, very high impact resistance.  Heat treated 4140 might also be a good choice, it is more or less the go-to standard for high performance steels.

 

There is one dimensional change I would consider making to the bolt: I would increase the fillet radius at the vertex of the acute angle at the rear of the cutout.  This would necessitate a corresponding revision to the radius on the tip of the lug on the action bar that engages the bolt cutout.  You'd be playing with fire on this one since the geometry that area appears to be critical to function of the Reising. 


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#10 Bridgeport28A1

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Posted 17 May 2019 - 12:34 PM

I had an old school "retired" gunsmith silver solder my Reising bolt that had sheared of the bottom rear of the bolt. I haven't used it since the repair as it is #2 back up bolt. Not sure how the repair will stand up as I don't have any immediate plans on shooting the repaired bolt. For what it is worth my gunsmith said the steel on broken bolt was very hard.


Edited by Bridgeport28A1, 17 May 2019 - 12:40 PM.

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#11 BillyDixon

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Posted 17 May 2019 - 04:20 PM

we dad bought several reising bolts from numrich..the outside diamiter was way over size and bolts still had burrs from machining, these appear to be unfinished bolts.. we ran them thru our centerless grinder to bring the out side diamiter to whatwas factory spec. they ran fine. i think numrich sold a lot of reising parts that were factory scrap or not finished, stuff that tthey got years ago when they bought out H+R.  numrich  assembled a bunch of reisings with registered recievers they got from H+R, and had stocks made in italy, at one time i think numrich was selling these reisings for something like 300.00 in shotgun news, just sayn


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