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Pedersoli Sharps chamber pressures?

 
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  #1  
Old 10-02-2010, 09:46 PM
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Pedersoli Sharps chamber pressures?

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
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Old 10-03-2010, 05:41 PM
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Re: Pedersoli Sharps chamber pressures?

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
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Old 10-03-2010, 07:05 PM
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Re: Pedersoli Sharps chamber pressures?

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.
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Last edited by shortgrass; 10-04-2010 at 06:50 PM.
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Old 10-04-2010, 09:23 PM
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Re: Pedersoli Sharps chamber pressures?

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
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Old 10-05-2010, 01:02 AM
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Re: Pedersoli Sharps chamber pressures?

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.
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Last edited by shortgrass; 10-05-2010 at 01:25 AM.
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Old 10-05-2010, 12:17 PM
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Re: Pedersoli Sharps chamber pressures?

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

Tom
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Old 10-07-2010, 04:33 PM
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Re: Pedersoli Sharps chamber pressures?

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
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