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spring assembly in M53 bolt

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CRUSADER
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Re: spring assembly in M53 bolt

Postby CRUSADER » Mon May 17, 2010 2:48 pm

Mr. Naess,

I also have Myrvang's book. It is indeed a great resource. However, somehow or another I got it into my head that the bolt catch device was developed & actually saw use during the war. After re-reading part of the book this afternoon, it is clear that you are correct. While the device saw some development during the war, it appears that it never went any further than that. Page 163 shows the prototype. Thanks for correcting my memory today! :D

What have you seen as far as running a MG42 type recuperator in a gun used to fire 7.62 NATO? Do the recuperators operate well?

What is the best way to go about contacting you about having a recuperator or two rebuilt with your new springs?

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Re: spring assembly in M53 bolt

Postby bmg17a1 » Mon May 17, 2010 11:05 pm

You can send the recuperators to:

Black River Militaria
P.O. Box 471
Cavendish, VT
05142
802-226-7204

I have not experienced any significant difference in overall function using .308 in an MG42 with the standard recuperator, given that all else is in good mechanical condition and using good ammo.
The springs are made to a greater compressive resistance than a typical wartime spring within the following limitations. The limitaitons on the OD of the spring are the wire size, which is also limited by the OD of the coils, which have to allow fitting of the plungers. There are also limits to the radius of the coils for any given wire size. Other factors are spacing of the coils and length of the spring, given a specific spacing.
Anyway, the springs function well and hold up very well. Most of the recuperators I've rebuilt are used in FA 42s so they're getting a good workout.
Over the years, I've converted varioius of my 42s to .308 on occasion, using the full complement of MG3 parts except recuperators, of course.
Quite a few years ago, I acquired a registered Rheinmetall MG42/58, made in 1961, that was arsenal upgraded to MG3 specs by the Bundeswehr, and it is in .308. It has the MG3 recuperator, but I don't believe it was originally manufactured with the longer recuperator housing, although i can't find any info on the early post-war Rheinmetall MGs. I also had two post-sample Steyr MG74s, in .308, but only have one left, so, I shoot any of those in .308 and leave the 42s in 7.92.

Bob Naess

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Re: spring assembly in M53 bolt

Postby TactAdv » Tue May 18, 2010 12:33 am

bmg17a1 wrote:I also had two post-sample Steyr MG74s, in .308, but only have one left, so, I shoot any of those in .308 and leave the 42s in 7.92.

Bob Naess


I am sure the one '74 you got rid of has a nice home now. ;-)

BTW, interestingly enough, I can tell you quite specifically that running my wartime '42 receiver with a set of drop-in MG3 7.62mm parts is -NOT- the same "feeling" in the seat of the pants as running the stock MG-74 with temporary replacement of a std MG3 bolt/carrier/buffer so that the dynamics system matches the parts running in the MG-42 receiver running the same temporary parts combination.

While on first glance the only meaningful difference is the recuperator, there is more to it. I can't/won't/don't fully attribute the difference in "feeling" merely to the recuperator issue, there is something more to it that I haven't yet run down empirically.

-TomH

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Re: spring assembly in M53 bolt

Postby bmg17a1 » Tue May 18, 2010 2:08 pm

TH says:
I am sure the one '74 you got rid of has a nice home now. ;-)

Couldn't have gone to a better home! The letters I get from the 74 about the posh accomodations, TL care and the smiling face of the owner are gratifying, not to mention all the brother MGs for companionship.

Meanwhile, back at the ranch:
There are lots of variables between the 74 and the 42 that would need consideration and understanding to make any meaningful comparison, but in my opinion, such comparisons are generally meaningless anyway. Seat of the pants differences in feel just between 42s can be downright amazing. The .308 42/58 is smooth as butter compared the 7.92 guns, and more so than the 74. I like the physicality of the 42 types and enjoy the ride.

Bob

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Re: spring assembly in M53 bolt

Postby TactAdv » Tue May 18, 2010 2:54 pm

bmg17a1 wrote:There are lots of variables between the 74 and the 42 that would need consideration and understanding to make any meaningful comparison, but in my opinion, such comparisons are generally meaningless anyway. Seat of the pants differences in feel just between 42s can be downright amazing. The .308 42/58 is smooth as butter compared the 7.92 guns, and more so than the 74. I like the physicality of the 42 types and enjoy the ride.

Bob


I've often opined that, like any roller locked gun, it is the unique contact angle of any unique locking wedge facing any given roller that controls the personality of the gun. The entire roller locking concept, being an unlocked delayed blow-back action, is entirely dependent upon the absolute part-to-part consistency of the angular relationships of resistance. That any 2 guns would "feel" and thus be responding to the recoil impulses differently is entirely consistent with the notion of simple differential wear of the parts....rollers, locking recesses, face angle of the locking wedge, etc., that with each minute variation results in a new synergy of the entire system.

The "feel" part of shooting these guns is largely due to the unique pathways taken of the transmitted recoil forces as they progress through the angular translations of the locking parts. Change, alter, or modify any one pathway even slightly, say, from an asymmetrically worn locking wedge face, and that gun now will display a unique recoil as it does not match anymore the carefully calculated pathways of force that appeared on the designers original sketches. Bolt rollers are troubling in that they wear down with use. Same for the locking recesses in -some- barrel extensions. A lot of this is exacerbated by another of the synergy parts, the recuperator assembly, being ignored as it suffers the effects of aging and use, too. Lose any of the original force balancing inherent in new parts....and synergistically the problems will manifest themselves in the other effected areas.

Point being here is that all of the locking system parts contribute to the "feel" of the recoil impulse, and that it is likely hard to compare any two guns as Bob says. Given a range of different guns, all that really matters is that any unique set of locking system parts perform well ENOUGH to keep the margins of safely intact, breech pressure safely contained, unlocking dwell within safe periods, etc. If the locking forces are too well contained the gun will run "rough" as it takes comparatively more absolute force to cause the rollers to disengage, if the locking system parts allow unlocking to begin too soon- from worn, incorrect, or improper parts used...Bad Things(tm) can happen. One of the things about a "smooth" running gun is that it shows a nearly perfect balance (currently) exists in the synergy of the locking system component parts.

That a MG-42 running .308 ammo will seem "smoother" than the same gun running 8mm is not strange as the original design of the locking system synergy for the recoil impulse of the 8mm cartridge's peak pressures (which one must intimately understand was TOTALLY relevant to the GERMAN'S idea of their own proprietary propellants and attendant properties only) was intended to be balanced for the lower absolute impulse of their cartridges compared to the later 7.62 NATO M80 round. An important realization is to remember that the whole reason the initial development of the T65 cartridge came about was due to a discovery of how to better prepare propellant formulations for energies relative to bulk. IOW's the newer propellants contained similar energies as earlier propellants in a form that had less physical bulk. That chemical property change, resultant in differing deflagration characteristics, is what makes recoil impulse of the 7.62 NATO give different operating "feel' through the locking system.

-TomH

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Re: spring assembly in M53 bolt

Postby bmg17a1 » Thu May 20, 2010 1:16 pm

Some further observations follwing Tom's very interesting post. Part of the incurable harshness of the 42 is the impact of inner rear face of the barrel extension against the tips of the cam bosses on the curved piece (trunnion). The design of the 42 is somewhat crude in this respect, since there is no practical or easy way to eliminate the impact or even reduce it significantly in produciton or as an after production modification. The high rate of fire amplifies this impact, and deterioration of the recuperator springs also increases the severity of the impact. The vibration created by this impact is quite destructive over a long period of time. I don't have much science to back this up, but the hardened steel of the curved piece being struck agains the hardened steel "anvil' of the barerl extension probalby creates some rather potent high frequency vibrations that will be absorbed by the pressed steel fo the receiver and any pressed. stressed or welded areas will suffer.
Increasing the vibration and its destructive potential is the bolt and its impact on the buffer. The vibratiion caused by the collision of these various heavy and hard parts causes loosening of various rivets, such as rail, barrel stop, rear sight, popping of rivet heads and cracking of various areas like the webs between the shroud vent holes, the die formed waist at the muzzle that holds the bearing sleev inplace and elsewhere.
It is wise to remember that these MGs were "throw away" weapons, designed cleverly, but also built of fairly fragile materials using fast produciton techniques, ,and using a design that is close to the edge of malfunction while firing and highly self-destructive. Low cost, fast production, and conservation of materials creates a weapon that isn't supposed to last very long. There's some irony in the fact that such a devasting high rpm weapon became a priority target, with the average life expectency of an MG42 gunner at about 24 hours. With this odd consequence of the 42s unique character, gunners didn't survive long and, many of these guns remained after the war without having seen really heavy use. Compared to Chau Chats, which were very heavily used, the MG42s mostly are in great condition. ammo supply was a ocnstant problem and operator discipline broke donw pretty quickly under combat, so it seems that many 42s survived the war ijn good cnditon for us collectors.

Bob Naess

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Re: spring assembly in M53 bolt

Postby BDE » Fri May 21, 2010 5:27 pm

What would be need to switch over a 8 mm SA 42 to 308 ?

Thanks
Brian

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Re: spring assembly in M53 bolt

Postby bmg17a1 » Fri May 21, 2010 6:43 pm

MG1 and MG3 parts can be used. I am partial to the MG3 topcover, comnpared to the MG1 parts, as it has a holdopen device in the hinge, and also the MG3 feedtray with the extra belt holding pawl and box bracket. And, of course the .308 barrel and booster/flash-hider, both of which are used with any post war 42. there are lots of Steyr .308 barrels out there, but if you buy one test the headspace as some of them can be extremely tight with the boltface binding agianst the breechface on lockup.

Good luck.

Bob Naess

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Re: spring assembly in M53 bolt

Postby MGMichael » Mon Jun 28, 2010 7:22 pm

I posted a lot of detail on MG42 recuperators, springs and keepers, as well as firing pins, in a thread on this forum last July. It can be found with the search function.

M

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Re: spring assembly in M53 bolt

Postby tomcatshaas » Mon Jun 28, 2010 8:39 pm

A little trick. You can go into your own profile and search your own posts.

viewtopic.php?f=9&t=8862&p=67743#p67743


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