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Rifles, Reloading, Optics, Equipment
Gunsmithing
Pedersoli Sharps chamber pressures?
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<blockquote data-quote="specweldtom" data-source="post: 430932" data-attributes="member: 2580"><p>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.</p><p></p><p>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.</p><p></p><p>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.</p><p>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.</p><p></p><p>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?</p><p> </p><p>I apologize for getting so long-winded, and if I have miss-stated something, please correct me.</p><p></p><p>Thanks again to all, Tom</p></blockquote><p></p>
[QUOTE="specweldtom, post: 430932, member: 2580"] 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 [/QUOTE]
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