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Pedersoli Sharps chamber pressures?

 
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  #8  
Old 10-07-2010, 06:22 PM
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Re: Pedersoli Sharps chamber pressures?

Gary, shortgrass has been very helpful on the color case hardening process. 8620 is one of the metals that responds very well to CCH. I have a lot of faith in that steel and would be impressed if that is what Pedersoli uses. Other than cr-moly, which may not take color case very well, it would be the best choice in my mind. I have recommended that the owner keep loads below the 29,000 psi that Pedersoli lists as maximum, but have a nagging feeling that their Sharps replicas are underrated by them.

Thanks for the info. If you find out more, let us know. I forgot to check the number of views, but a fair number of people are checking it out.

Thanks to all, Tom
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  #9  
Old 10-08-2010, 10:47 AM
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Re: Pedersoli Sharps chamber pressures?

Quote:
Originally Posted by specweldtom View Post
Gary, shortgrass has been very helpful on the color case hardening process. 8620 is one of the metals that responds very well to CCH. I have a lot of faith in that steel and would be impressed if that is what Pedersoli uses. Other than cr-moly, which may not take color case very well, it would be the best choice in my mind. I have recommended that the owner keep loads below the 29,000 psi that Pedersoli lists as maximum, but have a nagging feeling that their Sharps replicas are underrated by them.

Thanks for the info. If you find out more, let us know. I forgot to check the number of views, but a fair number of people are checking it out.

Thanks to all, Tom
most folks like to use 8620 in machining processes because of it machining properties. I am too damned lazy to go out to the garage and get a steel handbook to see what's in it, but it does seem like it has a good bit of sulphur in it. It's not gummy when you cut it like 1020. It's a good steel for sure, and in low pressure apps; you can't beat it. Still if I were cutting a Sharps reciever, I think I'd start with a 4350 or even 4150 billet; and be done with it. In the end your money ahead when you look at heat treating the metal as well as a normalizing process in the middle.
Most all the guys I know that shoot the Pedersoli use nothing but black powder for 600 thru 1000 yard target shooting (per the rules). Two guys I know of shoot rebarreled ones in 40-65 and 45-60, and never miss the gong. (HOW?) Myself, I'm a Hi-Wall person from the get go!
gary
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  #10  
Old 10-08-2010, 05:01 PM
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Re: Pedersoli Sharps chamber pressures?

I agree on first choice being cr-moly or cr-ni-moly. As I recall, the old SAE, now AISI system, assigned a number to a steel or alloy steel that used the first two digits to identify the material and the second two digits specified the carbon content in 100ths of a percent (points) so that when you looked it up in the handbook, the first two digits of 8620 would list the chemistry of the steel including the carbon content, which you already knew from last two digits (20 /100ths of a percent carbon). It may just naturally be a good material to machine, because any intentional re-sulphurization (for free-machining) would be very detrimental to its mechanical properties after a high temperature heat treat. Gary, you mentioned 1020, which would now be AISI 1020, and best I can recall, is just a cold-rolled mild steel with a touch of manganese and .02% carbon. I've also heard other people say that it doesn't machine cleanly.

On the cr-moly, 4130 is a low cr, moly alloy with .03% carbon, and 4140, 4150 are the same alloy except with more carbon. The higher carbon content makes them more hardenable, but not tougher at the same hardness. 4340 is a low cr, ni, mo alloy that has similar hardenability to 4140, but with improved toughness. I don't remember the specific requirements, but I do remember that there is a special grade of 4340 that is called "aircraft grade". All I can remember about it is that it is really good stuff, and was developed to meet aeronautics industry requirements.

One of the reasons I like 8620 is that U.S. Garand and M-14 receivers are case hardened 8620 forgings. If it gets it done for them, It's got to be good stuff.
I recall back when the Chinese M-14 clones were imported, they got bad-rapped for being too soft. Turns out that they were cr-moly forgings and were being thru-hardened by quench and temper. Their only problem was that although they were strong and tough, they didn't have the wear resistance of the case hardened 8620 forgings, or the civilian made castings. They had some other problems too, but basic receiver metallurgy wasn't one of them.

Overall, the question of choice of material for the Pedersoli replica black powder guns has led to an exchange of information that has been very beneficial to me, and has taken some interesting detours, not the least of which is this one. The question of using black powder or black powder substitute caused me to advise someone to avoid black powder in a fine rifle. That was just my opinion, but it was all I had. I know that many great shooters are purists about using black powder only, and many fine guns have never shot anything else, but I still haven't changed my mind, and could not advise someone to shoot black powder in their rifle if I wouldn't.That is what got us off into this thread. If you chose to shoot smokeless, what were safe pressures, which led logically to what are they made of and how strong are they?

I apologize for getting so long-winded, and if I have miss-stated something, please correct me.

Thanks again to all, Tom
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  #11  
Old 10-09-2010, 11:11 AM
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Re: Pedersoli Sharps chamber pressures?

Quote:
Originally Posted by specweldtom View Post
I agree on first choice being cr-moly or cr-ni-moly. As I recall, the old SAE, now AISI system, assigned a number to a steel or alloy steel that used the first two digits to identify the material and the second two digits specified the carbon content in 100ths of a percent (points) so that when you looked it up in the handbook, the first two digits of 8620 would list the chemistry of the steel including the carbon content, which you already knew from last two digits (20 /100ths of a percent carbon). It may just naturally be a good material to machine, because any intentional re-sulphurization (for free-machining) would be very detrimental to its mechanical properties after a high temperature heat treat. Gary, you mentioned 1020, which would now be AISI 1020, and best I can recall, is just a cold-rolled mild steel with a touch of manganese and .02% carbon. I've also heard other people say that it doesn't machine cleanly.

On the cr-moly, 4130 is a low cr, moly alloy with .03% carbon, and 4140, 4150 are the same alloy except with more carbon. The higher carbon content makes them more hardenable, but not tougher at the same hardness. 4340 is a low cr, ni, mo alloy that has similar hardenability to 4140, but with improved toughness. I don't remember the specific requirements, but I do remember that there is a special grade of 4340 that is called "aircraft grade". All I can remember about it is that it is really good stuff, and was developed to meet aeronautics industry requirements.

One of the reasons I like 8620 is that U.S. Garand and M-14 receivers are case hardened 8620 forgings. If it gets it done for them, It's got to be good stuff.
I recall back when the Chinese M-14 clones were imported, they got bad-rapped for being too soft. Turns out that they were cr-moly forgings and were being thru-hardened by quench and temper. Their only problem was that although they were strong and tough, they didn't have the wear resistance of the case hardened 8620 forgings, or the civilian made castings. They had some other problems too, but basic receiver metallurgy wasn't one of them.

Overall, the question of choice of material for the Pedersoli replica black powder guns has led to an exchange of information that has been very beneficial to me, and has taken some interesting detours, not the least of which is this one. The question of using black powder or black powder substitute caused me to advise someone to avoid black powder in a fine rifle. That was just my opinion, but it was all I had. I know that many great shooters are purists about using black powder only, and many fine guns have never shot anything else, but I still haven't changed my mind, and could not advise someone to shoot black powder in their rifle if I wouldn't.That is what got us off into this thread. If you chose to shoot smokeless, what were safe pressures, which led logically to what are they made of and how strong are they?

I apologize for getting so long-winded, and if I have miss-stated something, please correct me.

Thanks again to all, Tom
Tom, an excellent post!!

* 1020 0r 1018 is just plain old cold rolled steel like you said. Where as 8620 is a hot rolled steel with very good machining properties to it. You can carburize and harden 8620 (that is the process used to add a hard shell to the surface of 8620. But you can also just carburize it (this will imbed carbon into the surface), and then take it thru a nitride process (I rarely used this process). Now with the Chinese M14's being made of chrome moly steel, I now see something very interesting! One could dissassemble the rifle, and then take the reciever and a few other choice items (bolt carrier and gas piston assembly come to mind) and have them nitrided for about a .012" to a .018" case. Takes about one full day at the max. The action sizes will change little if any when done correctly. (note: I have had some steels shrink about .0009" and even a couple grow a similar amount!). I'm sure that's all the Fulton Armory is doing.
Back to Chi Com M14's a second. I doubt they are even doing a full hardening of the reciever group when all they needed was a piece of 4150 pretreat steel or even 4350 pretreat steel. C/M maxes out in the mid to low forties on the Rockwell C scale (I think 4350 may reach about 47 RC if it good quality stuff). A piece of 4150 or 4350 Pretreat steel is shipped 28-32RC (I used to buy the stuff by the truck loads), and it's all pretty much the same till you start machining it. The off shore steel is junk! But just as importantly, you can take a piece of 4150 and send it strait to nitride without ever doing anything else to it! 29 Hours in a good furnace at 900 degrees will get about .035" case that will go about 62RC.
Lastly, the United States has some very good steel producers. I like the pretreat stuff from Baldwin in PA the best by far! I've learned that if the steel is cheap the results are just as cheap. The very best steel sold out there period comes from Timken, but it's also the most expensive (you make that high cost up down the road)
gary
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  #12  
Old 10-12-2010, 09:13 PM
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Re: Pedersoli Sharps chamber pressures?

Gary, I've said many times; there's no substitute for experience! Thanks for following up!

Tom
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  #13  
Old 10-13-2010, 10:35 AM
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Re: Pedersoli Sharps chamber pressures?

Quote:
Originally Posted by specweldtom View Post
Gary, I've said many times; there's no substitute for experience! Thanks for following up!

Tom
sometime down the road I'll have to tell you about building my own action, and how it ended up cut in half. (I actually built two different actions)
gary
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