Pedersoli Sharps chamber pressures?

Discussion in 'Gunsmithing' started by specweldtom, Oct 2, 2010.

  1. specweldtom

    specweldtom Well-Known Member

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    Didn't know a better place to ask the question. I thought about the reloading or the muzzleloading board, but this forum seemed like the best place.

    Does anyone know what steel Pedersoli uses in their reproduction Sharps 1874 Buffalo rifles? Or of Rockwell or Brinnel testing on them? The question came up because in spite of the massive size of the frame and breechblock, Pedersoli says use black powder only. I'm wondering if it's a liability issue or a metallurgical limitation. Repros and even original Trapdoors can shoot factory smokeless loads, and Rolling Block repros are rated for more pressure than the Trapdoors. Physically, both appear to be fragile compared to the Sharps. I don't have the engineering skill to anaylyze them, but comparing geometry and size, it appears to me that the modern Sharps could potentially be stronger than even the modern Highwall or the #1 Ruger. If they aren't, their metallurgy and/or heat treat condition must be the limiting factor.

    I am not a purist, so if I had a $1500 Pedersoli Sharps, I wouldn't want to shoot black powder in it either. The owner looked for Pyrodex and Triple 7 cartridge loading data and didn't find it. I made that suggestion before looking at smokeless loads.

    Thanks for any help. Tom
     
  2. specweldtom

    specweldtom Well-Known Member

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    Update: I found some good info that answers part of my question.

    I don't know how to post links, but if you search for "Pedersoli proof test rules and allowable limits", it is very informative.

    1st, Pedersoli cartridge rifles are NOT marked "for black powder only".

    2nd, they allow up to 29,000 CUP's or PSI. Also, they proof test at 30% over that pressure. That comes out at 37,700 PSI. Since the rifle must survive this pressure without any damage in order to be sold, it seems that the 29,000 PSI limit is quite safe. I'm still surprised that it's not higher, but it does indicate that the materials used are probably low to medium carbon steels and not chrome-moly or chrome-nickel-moly high strength steel.

    3rd, they allow the use of major brand commercial .45-70 factory loads. They do not endorse reloads. I did read on another search that .45-70 ammo loaded by Garrett is too hot for these old designs.

    On the metallurgical part of the question, they only say that due to the use of modern steels and some redesign, their replicas are stronger than the originals.

    If you're interested in this subject, it's worth finding and reading the whole article.

    The question of using smokeless ammo has been answered, but I'd still like to know more about the metallurgy used. I'm pretty impressed by these rifles.

    Good hunting, Tom
     

  3. shortgrass

    shortgrass Well-Known Member

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    Interesting questions , Tom. I'm always interested in stuff like this. Ya' gotta' admit steel is better today, with fewer impurities, than ever before, even if it is made in 'lower wage' areas or places where modern technology has been put to use. I guess if you're ordering your steel in big enough quantities you can get the 'blend' you specify. I've done alot of color case hardening and alot of trying this and that to see what works and what doesn't. Much depends on the 'carbon rich media' you are using to 'pack' your parts in. As it's organic material (bone charcoal, wood charcoal) there are no set standards and there can be great variations from lot to lot. As much depends on the steel. Again, when you're buying in quantity, you can specify what you want and get it. As for the actual process, heck, even my oven has digital controls. When the originals were made they might not of even used a pyrometer and depended on the 'skill' of the operator. Low to medium carbon steels, with a carbon content of no more than .35% respond to the old fashioned methods of 'color case hardening' very well. Unfortunately, the only way I know of to find out how thick the 'case' is , is to cut through and measure it (destructive). The sample part can be put under a "Rockwell" tester for a hardness check but, there seems to be much disagreement as to the validity of that test on case hardening. I would tend to think the reciever on that Pedersoli would be perfectly safe with standard factory .45-70 loads whether loaded with black or smokeless powder. I don't think there's a major manufacturer today that will sanction the use of reloaded ammo in their firearms. Too many guys load 'dynamite'! Single shot black powder cartridge rifles, no belt, no Berger Bullets, no 20 M.O.A. rail,,,,,just paper patched lead.
     
    Last edited: Oct 4, 2010
  4. specweldtom

    specweldtom Well-Known Member

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    Shortgrass, many years ago, I worked as a weldor in an industrial shop that also had a very good blacksmith shop. I had the opportunity to do some tool dressing, forge work, and heat treating. We mostly did thru-hardening on O1 tool steel, but occasionally did some case hardening with a material called Casenite. We only had a Rockwell tester, and best I can remember, only used the diamond braille, usually in the C scale. On objects that couldn't be destructively tested by removing a small area of the case, we would run a "witness" pc of the same material together with the production piece. We would have the machine shop progressively cut away the case in narrow strips on a surface grinder and then send it to the metallurgists. They could do microhardness tests to determine the depth of the case, the case hardness, and the hardness of the underlying base metal. Because of their experience, some of the old blacksmiths were very good at hitting the hardness and depth of the case. I still think it was 10% science and 90% art.

    I believe that you are correct that the Rockwell diamond braille will punch through the case, at least partially, and give a false reading. I also believe that a Brinnel tester would give better information about the underlying hardness and consequently a better idea about the strength and toughness of the core of the part, but would also be skewed by the case hardness and depth. Brinell testing also leaves a noticeable dent in the part tested.

    Bottom line to this novel is that short of information from the factory, I don't know a good way to find out if the steel itself has enough carbon to strengthen during the quench or not. The published Pedersoli allowable chamber pressure has to be accepted, regardless of how strong the Sharps action looks. I will say that it is astounding that they rate their Trapdoors and Rolling Blocks at the same pressure. No way they are as strong as the Sharps. Oh well, 29,000 psi can get it done.

    By the way, I don't remember us ever getting the strong color variations when we case hardened. I'm betting that IS art. It's also the prettiest finish on a gun part that there is.

    Thanks for jumping in. Looks like it may be a dead topic. Tom
     
  5. shortgrass

    shortgrass Well-Known Member

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    I've used the Casenite before on small parts that need some hardness, the only color it seems to leave is gray. True "color case hardening" is having the part you want to harden 'packed' in a crucible with carbon rich material such as bone or wood charcoal and heating in a heat treat oven to between 1335 deg. & about 1400 deg. for a predetermined length of time. Charcoal made of leather was used at one time in the past but, since chromium is now used in the tanning process, it no longer is used or desirable, needs to be 'brain tanned' leather. (Cyinide 'salts' were and are still used today, but that's not a process I deal with. I 'm not sure if 'salts ' transfer any 'color', either.) When you get the crucible and its contents up to 'heat' carbon transfers to the surface of the part you are heat treating (the crucible is a sealed container and the part(s) and charcoal inside have to be 'packed' in a certain way, very tightly, so as to eliminate as much air as possible to prevent oxidation and combustion). I've never heard a resonable explination of where the colors come from, could be the impurities from the charcoal, who knows, but I do know, different charcoals produce different colors and different hardness. I have found very little technical information in print, some good stories and basic info, though. Most of what was known by the men of the past that did the work was kept in their heads or personal note book and was lost when they pasted. The story goes, When Colt decided to re-intoduce the SAA they had to run an extensive R&D program for the case hardening, there was no or very little technical info from the past. Another story goes, When Colonel Hatcher took over operations at the Springfield Armory (the Springfield '03 was in production then) he discovered that the temps were being judged by the operator visually in the case hardening process. After installing the then new pyrometers as much as a 200deg. could be possible just because of a cloudy day. Heat treat got better after the pyrometers were installed. Alot of this is art to this day. It takes alot of time and failures to get even a slight handle on the process. I learned the basics at a NRA Summer week long class, but spent the next two years, off and on, refining to the point I felt comfortable doing a Rolling Block or a box lock shotgun action. Part of the high cost of doing color case hardening today is in making the blocks/braces for parts of thin section that will warp out of control if not blocked of braced. Going from above 1330 deg. to air temp fresh water tends to do that. The blocks/braces don't last very long as they warp too. Those nice "Case Colors" of yesteryear were and are a by-product of the hardening process. Some of the high quality guns of the day had the color polished off and then they were rust blued. Those 'colors' can be had with a modern chemical process, but I know nothing about it. I'd be glad to e-mail some of the articals I have a accumulated over the years if you would like, just PM me an e-mail address where I can send attachments. You're right, it's a 'dead' topic on this forum, not 'magnum' enough , I guess.
     
    Last edited: Oct 5, 2010
  6. specweldtom

    specweldtom Well-Known Member

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    I'll P/M you my email address. I appreciate you taking so much time.

    Tom
     
  7. Trickymissfit

    Trickymissfit Well-Known Member

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    four years ago, I could have found out exactly what kind of steel they used as I worked with several big name metalic shooters that used them as well as the real Sharps rifles. Looking one over my guess is that they are using some kind of hot rolled steel, and to take it a step further my guess is 8620. The ones I have looked at up close seem to have a slightly pourus surface, just like 8620. And the strength factor fall right inline as well. 8620 will carburize for upto .035" case, but doubt they are doing much more than .005" to .012", if any at all. Add to this the fact that at least one well known manufacturer of Hi-Walls and Lo-Walls over here uses nothing but 8620 for their recievers leads me into this direction. But it's also possible that they are using a cast steel reciever, or even a forging of somekind of low alloy steel (like 8620). Of course they also could be going the other route and use a block of 4150 pre-treat for the reciever. It too has that pourus surface. But 4150 is much stronger than 8620 or even cast steel
    gary
     
  8. specweldtom

    specweldtom Well-Known Member

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    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
     
  9. Trickymissfit

    Trickymissfit Well-Known Member

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    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
     
  10. specweldtom

    specweldtom Well-Known Member

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    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
     
  11. Trickymissfit

    Trickymissfit Well-Known Member

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    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
     
  12. specweldtom

    specweldtom Well-Known Member

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

    Tom
     
  13. Trickymissfit

    Trickymissfit Well-Known Member

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    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