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Post by flyfisherman246 on Jun 13, 2021 8:21:32 GMT -5
I am looking to make a 5 shot oversize cylinder out of 4140 for a blackhawk to be chambered in .500 linebaugh. I have read guys are hardening cylinders around 42 RC. How is this number determined as a good compromise between yield strength and toughness? The yield strength of 4140 at 42 RC is 170 ksi.
I took a super blackhawk and determined the center of the chambers are about .542" from the center of the cylinder. Now with an oversize 1.800" cylinder that would put a .500 Linebaugh's wall thickness to about .085" thick to the outside edge. I ran the numbers for hoop stress on a thick walled pressure cylinder with an inside radius of .265 and an outside radius of .349 and the internal pressure of the .500's max pressure of 36 ksi. I got a hoop stress of 134 ksi. This is assuming constant steady pressure and not accounting for heat and impact associated with a round being fired. This gives a safety factor of 1.27. Now if I run it with a proof load of 30% over max (46.8 ksi) the hoop stress is 174 ksi which is higher than the yield strength of 42 RC at 170 ksi which would theoretically bulge the cylinder.
I'm not at all claiming to be an expert at this stuff, I'm legitimately curious where I'm going wrong with my numbers. Surely the .500 linebaugh wouldn't be approved by saami if they couldn't fire a proof load through them without bulging. I'd like to get a better understanding of this and have the numbers line up before I put all the work into a revolver only hoping it doesn't blow up.
Thanks for the help
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Post by mike454 on Jun 13, 2021 9:15:19 GMT -5
Doesn't answer your question, but the 500 Linebaugh isn't a SAAMI approved cartridge.
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Post by flyfisherman246 on Jun 13, 2021 9:30:34 GMT -5
Doesn't answer your question, but the 500 Linebaugh isn't a SAAMI approved cartridge. Did not know that. I figured if hornady was making brass and buffalo bore and grizzly selling factory ammo it would be. Leaned something. thank you |
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Post by mike454 on Jun 13, 2021 10:51:30 GMT -5
My impression is that the 500 Linebaugh guns have about the same cylinder wall thickness at the 45 colt Ruger factory cylinders. Of course the Linebaugh's don't have the bolt notch over the chamber so should be stronger. The Linebaugh and Ruger only 45 colt loads run in the same general pressure. Not sure why the Linebaugh wouldn't be able to contain the same pressures and I don't believe I've ever heard of one letting go absent a handloading accident. I could be misremembering some of these measurements so don't take them as gospel.
"Theory and practice sometimes clash. And when that happens, theory loses."
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Post by flyfisherman246 on Jun 13, 2021 14:38:31 GMT -5
There has to be more to it than the numbers I'm running. Does the cylinder walls take the full force of hoop stress?
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Post by zeus on Jun 13, 2021 16:55:26 GMT -5
You should read some of John L’s old articles. Maybe start with something other than one that will hurt you if it comes apart?
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Post by leftysixgun on Jun 13, 2021 17:43:27 GMT -5
Why not use a stronger tougher steel for the safety margin?
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Post by Lee Martin on Jun 13, 2021 18:16:44 GMT -5
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Post by flyfisherman246 on Jun 15, 2021 4:07:12 GMT -5
That page is very informative. Thank you for sharing that information. I'm not at all doubting you on it, I'm just curious for myself. How do you come up with the hardness numbers you use on these cylinders? I understand its a balance between yield strength and toughness, but how was this determined. Thanks for the help, I really appreciate it.
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Post by Lee Martin on Jun 15, 2021 8:29:47 GMT -5
How do you come up with the hardness numbers you use on these cylinders? We have a Rockwell hardness tester. -Lee www.singleactions.com"Chasing perfection five shots at a time" |
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Post by mike454 on Jun 15, 2021 9:26:39 GMT -5
That page is very informative. Thank you for sharing that information. I'm not at all doubting you on it, I'm just curious for myself. How do you come up with the hardness numbers you use on these cylinders? I understand its a balance between yield strength and toughness, but how was this determined. Thanks for the help, I really appreciate it. Get a copy of the ASM heat treaters guide. If that doesn't provide the illumination you require you would need to probably talk to a metallurgist. I know Linebaugh has consulted with metallurgists over the years as have other smiths I'm sure. I have a colt SAA he built 35 years with an oversize cylinder to take Ruger loads. He told me if he built that gun now he would have used a different steel because the steel he used wasn't great at handling hoop stress, which he discovered in consultation with a metallurgist. |
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Post by flyingzebra on Jun 15, 2021 9:44:11 GMT -5
... which he discovered in consultation with a metallurgist. *And* which you have not discovered via failure of the gun. :-) |
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Post by mike454 on Jun 15, 2021 9:53:33 GMT -5
Correct!
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Post by RDW on Jun 16, 2021 19:46:52 GMT -5
I am looking to make a 5 shot oversize cylinder out of 4140 for a blackhawk to be chambered in .500 linebaugh. I have read guys are hardening cylinders around 42 RC. How is this number determined as a good compromise between yield strength and toughness? The yield strength of 4140 at 42 RC is 170 ksi. I took a super blackhawk and determined the center of the chambers are about .542" from the center of the cylinder. Now with an oversize 1.800" cylinder that would put a .500 Linebaugh's wall thickness to about .085" thick to the outside edge. I ran the numbers for hoop stress on a thick walled pressure cylinder with an inside radius of .265 and an outside radius of .349 and the internal pressure of the .500's max pressure of 36 ksi. I got a hoop stress of 134 ksi. This is assuming constant steady pressure and not accounting for heat and impact associated with a round being fired. This gives a safety factor of 1.27. Now if I run it with a proof load of 30% over max (46.8 ksi) the hoop stress is 174 ksi which is higher than the yield strength of 42 RC at 170 ksi which would theoretically bulge the cylinder. I'm not at all claiming to be an expert at this stuff, I'm legitimately curious where I'm going wrong with my numbers. Surely the .500 linebaugh wouldn't be approved by saami if they couldn't fire a proof load through them without bulging. I'd like to get a better understanding of this and have the numbers line up before I put all the work into a revolver only hoping it doesn't blow up. Thanks for the help There is much more to the story of these monster bore magnums than meets the eye! For clarification only, By print and by countless averaging the bore to center is .546" and by the way your on paper numbers are correct! Good math there fly fisherman! But, But! There is something to be said for proof loads. However i guess i would ask you, why would you want to proof load a 500L when we have had such great luck with 17-4 ph and 4140 for a cylinder material. just asking Buddy. Ive built over a hundred of them, there is no telling how many john has made or david and hamilton. To answer your question of how is this number determined i guess it would be best said that when we were bugging these out and trying not to blow our selves up, we tested the best materials on the market during the 80s and this is what we have just stuck with. Theory is great but a smidge of trial and error has been our best teacher. One thing i would like to point out is that the massive bore size is a factor that has to be considered with the 500 L. Example. I am a top fuel slash nitro funnycar guy now most of my adult life. thru the 80s we battled it out with each other with power. Somewhere in the 2 to 3 thousand horsepower range. We had a two speed transmissions then and thru out the 90s we realized that with more power we didnt need two speeds anymore so we went to duel mags, bigger pumps ( more nitro) A multi disc shreddable type clutch and boy did the fun begin!!!!! By the end of the first decade of the new millennia we were all making over 10,000 HP. Its even worse now. we cannot really dyno test these things anymore because at about 11,000 HP we twist the end of the crankshaft off. So you cant load the engine up to get a full power reading! Austin coil had a special crank made with a 5" rear main and broke a train dyno in Florida at about 12,000 HP. The crank shaft doesnt break off in the car because the wheel load is allowing it to unwind the power being made. the tires are 36' tall and at about 240 mph they have grown to almost 5 feet. you go from about 115" of rollout to almost 200. Thats how we run 340 mph in a thousand feet under 4 seconds. You can only get so much h110 or w296 in the case behind any thing over 400 grains anyway and one of the reasons the pressure wont go in to outer space is because it has one hell of a big hole to get out of. Now i remember yappin with john one day in around 1990 and he had just put a cylinder back in one of his customers guns who had double charged a unique round. Big difference in the spiking pressure of a 14 grn load versus a 28, and it will fit in there. AND IT CAN GET REAL UGLY. HAHAHA. I have stuffed the 500 with the slower powders and never had any problem other than banged up knuckles. That is why i went the grip frame direction. to find a better way to hang on to em! I have a ruger that i built in the 90s that uses a 348 winchester case cut to about 1.550' and knecked down to .430 . I call it the 44 ronnie super stupid. its overall case length comes out to 1.425" and it is a terrorist. Fermin loves it. I would venture to say that if i made a 500 grain 44 cal bullet, (Probably be about an inch and a quarter long) that it would blow me straight to white mans Hell. to small a hole and to much friction in the bore. The pressure would spike way up there and it would be nasty! I mowed on a piece of carpenter last year and man o man is it a Beatchamahala to machine! The 500Linebaugh i beleive was a great idea that circled around the theory that a big ole Honkasaurus bullet even flying moderate speeds was not only a deep penetrator but it has one hell of a big smackaroonie factor because of the meplat surface which is bigger than most 44 cal bullets. hahaha. It has always been my favorite. Dont be afraid to tax the hell out of the 500l using those two infamous metals with your project. They have served us well. If you would like i will send you a copy of a builders print for the 5 shooter. its on my thread somewhere and its a great starting point. Gimme a hollar anytime if i can help. Ronnie ps 17-4 ph at h900 process to 42 RC is very elastic. And brownells # 84 will blue the heck out of it if you dont like the brown. |
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450ak
.30 Stingray
Posts: 458
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Post by 450ak on Jun 19, 2021 13:39:16 GMT -5
When I built the prototype model 89s I used 4140 heat treated to mid 30’s. Tried pretty hard to break one or stretch one. Didn’t happen. Yes I stuck cases and had to tap them out with a rod. Western powders said I was over 100k psi. Best to keep your mouth closed when shooting such loads it the recoil will close it......
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