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Military Firearm Restoration Corner

Receiver Hardness


rdfrench31

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I took everyone's advise and ordered a copy of "The Mauser Bolt Actions", and I must say you guys were right. This book is great. I have seen mention of receiver hardness mentioned several times already in this book. It seems that anytime the receiver is machined, filed, drilled, etc...care must be taken to avoid removing the layer of hardened steel. I know most everyone trues up the secondary torque shoulder, and many lap or face the primary torque shoulder. Then there in drillind and tapping for a scope...and removing the charging hump. My question is...at what point do you guys consider having the receiver heat treated? Also, how does one go about having it heat treated, is it a DIY or do you send it out to a specialist?

 

Thanks

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Well, as far as drilling and taping goes, don't worry about the heat treatment. If you're grinding off large parts of the receiver, well, that's something else.

 

Heat treating is a lost art anymore. If I recall, there are a couple of places that more or less specialize in heat treating old receivers like these Mausers, but I don't remember who it is anymore. Of course, sending a receiver is the same as sending a gun from a paperwork perspective. Ovens are available comercially for a few hundred if you want to experiment with it yourself.

 

I'm getting into DIY AK's, and from what I've read, what people are doing there is heat treating the receivers themselves with a torch and a bucket of oil. You don't do the whole receiver, just the key points like the holes, ejector and the top rail, and you only do that one at a time. You don't want to do that with something with as much boom as a 300 win mag, but 7.62 x 39 in an AK design is pretty tolerant.

 

So, I guess if you're just messing with a German/Yugo/Turk Mauser action, don't worry about it. If you are doing something that will require heat treating, or heat treating in the first place on a Mauser action like trying to build up a big, strong safe Spanish Mauser, send it to the specialist or just get a Yugo to start with, which will probalby cost you the same (or less).

 

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I'm no expert but have been hanging around this sight for about 5 years and this is what have learned regarding hardening.

 

The following operations DO NOT require rehardening.

a. Trueing the primary and or secondary torque shoulders.

b. Drilling and tapping for scope mounts.

c. Removing stripper clip hump.

 

The following operation DO require rehardening.

a. Trueing or lapping the recoil lugs.

b. Welding on the receiver ring.

c. Surface grinding the reciever ring.

 

This is not an all inclusive list and you wouldn't be hurting anything to have rehardening done to all sporterizing projects. I believe Kuhnhausen recomends it as a standard step in sporterizing Mausers.

 

Disclaimer: This is my opinion only and I have been known to be full of s__t!

Kenny

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Thanks for the replies fellas. My yugo 24/47 is still in transit, but here are the things I plan to do to it once it arrives.

 

- face the secondary torque shoulder

- true the primary torque shoulder

- lap the bolt lugs

- lap the bolt face

- mill off the stripper clip hump

- weld on a new bolt handle

- drill and tap for scope mounts

 

I just want to make sure I didn't weaken the receiver in a key area.

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kenak2,

I'm not saying you don't know what your talking about because you know more than me but is it a nessicity to re-harden the recoil lugs after laping or trueing? I've read books that say one doesn't have to. Just a thought. Walk me through your explanation.

Brenden

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kenak2,

I'm not saying you don't know what your talking about because you know more than me but is it a nessicity to re-harden the recoil lugs after laping or trueing? I've read books that say one doesn't have to. Just a thought. Walk me through your explanation.

Brenden

 

I assume you guys are talking about the bolt lugs. Like MD said I haven't heard of this either. I would think that only a minute amount of metal would need to be removed. Though, I am in no way an expert...so I could be way off base.

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I assume you guys are talking about the bolt lugs. Like MD said I haven't heard of this either. I would think that only a minute amount of metal would need to be removed. Though, I am in no way an expert...so I could be way off base.

 

You would think. Be forewarned that the case hardened layer on mausers can be very thin. In most cases no more than .010" deep, often less. Even removing .001" diminishes that layer by 10%.

 

PM me and I can take care of your hardening needs.

 

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z1r, who may know more than anyone else on this forum, is on record as always heat treating Mauser actions.

 

PM him for a referral to the best place.

 

flaco

 

Doubtfull, but I do know a lot about mausers anyway. :lol:

 

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kenak2,

I'm not saying you don't know what your talking about because you know more than me but is it a nessicity to re-harden the recoil lugs after laping or trueing? I've read books that say one doesn't have to. Just a thought. Walk me through your explanation.

Brenden

 

Like z1r said, the case hardening layer is very thin and by lapping the lugs you can and probably will wear through that layer.

It is my opinion, that the recoil lugs on the bolt as well as the receiver are the most critical areas regarding hardening.

Lack of hardening in these areas can lead to bolt set-back, which leads to case head seperation, which leads to potential injuries. Not to mention a ruined rifle.

Kenny

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Like z1r said, the case hardening layer is very thin and by lapping the lugs you can and probably will wear through that layer.

It is my opinion, that the recoil lugs on the bolt as well as the receiver are the most critical areas regarding hardening.

Lack of hardening in these areas can lead to bolt set-back, which leads to case head seperation, which leads to potential injuries. Not to mention a ruined rifle.

Kenny

I would say yes.. except that if you ever get case head separation... you already HAD a ruined rifle... or abused brass MV

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RD, welcome to the madness. I've been messing with my 1st Mauser for a little over a year. I learned 98% of what I know from these guys. It's an excellent group. Take the advice of many and do the metal work, then pm Z and follow up with the correct heat treat process. He'll know who should do it and what to ask for. I'm a newbie to Mausers, but have been involved with heat treating for over 20 yrs. I've heat treated alot of tooling with a torch or furnace and a 5 gal bucket of quench oil. Case hardening, especially a receiver, is a way different story. Hell, if it didn't crack, it would probably look like a pretzel! Leave that to those who do it for a living.

PS: My Turk was so soft, I made a fixture to hold it in a lathe, bored out the small ring threads and re-threaded to large ring dimensions. With a high speed tool bit! Cut like butter. Needless to say, when it's done it's getting re-case hardened. And not by me.

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RD, welcome to the madness. I've been messing with my 1st Mauser for a little over a year. I learned 98% of what I know from these guys. It's an excellent group. Take the advice of many and do the metal work, then pm Z and follow up with the correct heat treat process. He'll know who should do it and what to ask for. I'm a newbie to Mausers, but have been involved with heat treating for over 20 yrs. I've heat treated alot of tooling with a torch or furnace and a 5 gal bucket of quench oil. Case hardening, especially a receiver, is a way different story. Hell, if it didn't crack, it would probably look like a pretzel! Leave that to those who do it for a living.

PS: My Turk was so soft, I made a fixture to hold it in a lathe, bored out the small ring threads and re-threaded to large ring dimensions. With a high speed tool bit! Cut like butter. Needless to say, when it's done it's getting re-case hardened. And not by me.

 

madness is right...I'm starting to feel overwhelmed

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madness is right...I'm starting to feel overwhelmed

 

Like the Beastie boys said, slow and low, that is the tempo.

 

Sometimes it is best to start on an easy project. But, if your like the rest of us and like to bite off a lot, then just remember to chew. Take your time, think things out, and before you start on anything decide what exactly you want. Changing direction midstream will cost you more, delay the project, and often time lead to unexpected difficulties.

 

Read Kuhnhausens book with a grain of salt.

 

 

 

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I have a question on this subject. I have a commercial mauser action in 30-06 that survived a fire. Is it worth salvaging the action to build a rifle on? Will it need to be heat treated and who can do this for me? What about the bolt assembly? Would like to make this a project rifle if possible.What about the barrel that is still attached to the receiver? It appears to be OK except for needing to be refinished. does it need to be removed, and can I reuse it or do I need to buy a new barrel?

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Hi 762cavalier, there are questions as to how involved was the action in the fire. Was it stocked and if so, was the stock consumed in the fire. A big key here is the condition of the springs in the magazine, the bolt, and the ejector to name a few. If any of the springs are sacked, it obviously was subjected to excessive heat. I'm not sure if any parts are salvageable if they were indeed subjected to excessive heat, but perhaps others here can give you a better guess than I. Perhaps there is a test that you can do or have done to check the action's suitability. Like I said, I have more questions than answers.

 

Spiris

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Like the Beastie boys said, slow and low, that is the tempo.

 

Please Mike, no Beastie boys.lol. I've got a book around here somewhere that deals with rehardning, and a step by step project that is illiulstrated. I can see what you mean. 10% can be a significant amout, especially if your dealing with a gun that is 50+ years old. Thanks for the info everyone and opening my eyes.

Brenden

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Mike,

I take it you're not a huge fan of Kuhnhausens

 

Actually, I like his book the best. It's just that he obviously has a team of lawyers watching over him. Hence the warning.

 

I heat treat every mauser I build for myself and most clients. The cost is a drop in the bucket compared to the total cost of most builds I do. And unless the customer drops it off the side of a mountain it will still be in working order for his grandkids or even their kids. I've seen to many builds that were intended to be used frequently give up the ghost in short time. This sours the guy who commissioned a custom rifle and gives mausers a bad name. I'm of the opinion that anything worth doing is worth doing right.

 

Kuhnhausen can be a bit overly cautious. Which probably sounds funny coming from me.

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Hi 762cavalier, there are questions as to how involved was the action in the fire. Was it stocked and if so, was the stock consumed in the fire. A big key here is the condition of the springs in the magazine, the bolt, and the ejector to name a few. If any of the springs are sacked, it obviously was subjected to excessive heat. I'm not sure if any parts are salvageable if they were indeed subjected to excessive heat, but perhaps others here can give you a better guess than I. Perhaps there is a test that you can do or have done to check the action's suitability. Like I said, I have more questions than answers.

 

Spiris

I'm with Spiris on the springs as an indicator weather or not they have sagged.

I'd think that even if the action had gotten annealed by the fire, that it could still be

re-heattreated . If I had access to a machine shop that can test for hardness I'd get

it tested ( others chime in here ) I think that if it tests near 50 or at least 45+ "Rockwell"

it's OK. Here is something else I thought of as an indicator to the springs.

Pull the bullets and dump the powder on 5 ( a magazine full ) cartridges. If you can

"fire" all 5 primers without a misfire I'd say the odds are good that the springs are

still good and therefore the rest. Let me just say that I'd prefer the hardness test.

Per Jerry K 35C to 40C. Anyone know how the 'C' scale relates to the 'Rockwell' scale?

 

Tinker

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762, welcome to the Forum. Glad to have you aboard. You bring an interesting question.

 

Any commercial Mauser is worth a try at saving, within what you are willing or able to spend on it.

 

If it has been burned to an absolute crisp, then all is probably lost. However, if you have looked at the things the others have suggested and it still looks like there may be life in it, do one more thing. Look for warping. Get out a small straight edge and go around all the straight edges.

 

If it still looks good then I would consider using it after it has been re hardened (contact z1r). Before that is done get rid of the barrel and have it "trued". What is the condition of the springs? Mushy, good or shot?

 

If much heat got to the action then the bolt, also, would be of concern and should be sent for rehardening.

 

Anyway, consider what you paid for it and how much you want to spend. A good commercial is worth $200-400 depending on what trigger guard and a few other things it has (including the trigger if it survived).

 

If it has the military style bolt shroud and some funky mod of the mil trigger, go down. If it has a mil style tg, go down. But if it has a hinged magazine, adjustable trigger and commercial shroud, go up.

 

Good luck,

Brad

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Tinker, the C scale is Rockwell. There are many. Rockwell, Brinell, Knoop, Vickers and so on. Rockwell alone has several scales, C being the most common or "mentioned". The problem with these receivers and hardness testing is the C scale uses 150 kilogram load which is too heavy to pick up a .010" case. It punches through it, indicating "soft". You would be better served to use a Rockwell Superficial at 15 kilogram load, known as HR15N. The 15N scale is tough also because the impression is so small that any surface imperfections throw it off. Therefore the surface must be smooth and the part being checked must be sitting solid.

I would guess that when a place like Blanchards does an old Mauser, they are gas carburizing. The gas atmosphere reaches all areas equally so they either put a test pc in with it or check the recvr somewhere they can get a good reading. This is basically time and temp. The higher the temp and longer the soak, the deeper the case. Also the carbon potential of the gas effects this and case furnaces will usually have probes inside to monitor this.

762 - Very difficult to tell if a fire would lower the hardness. It certainly could. If the metal surfaces have scale on them, the hardness is gone. A rule of thumb in heat treating is that it takes 350 deg to temper something. That would be a minimum. Tempering can go as high as 1200 for certain steels. So all we need to figure out is how hot a fire is!! Another idea - where are you? Maybe you can send me the bolt. I possibly could tell something from it. I spent a day checking my Turk. Worst heat treat job I've ever checked. It's going to Blanchards!!!!!!!!

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Well I want to salvage it if I can. I couldn't beat the price, it was given to me.I got it as a barreled action, with the bolt and trigger. Don't know what happened to the stock. Doesn't appear to have any scaling and isn't warped.I will have to look at the bolt and spring. the trigger spring seems to be fine. I am located here in CA. I will try to post pics soon

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I've been following this thread and am a bit confused! When you say heat treating, I interpret that to mean heating the whole receiver to a high temperature and quenching. Grain structure would change throughout the metal and warping would be a real possibility? Or do you mean some sort of case or surface hardening? If so whats the process and who would I get to do it?

 

THANKS :rolleyes:

Don

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