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Thread: Bearing Friction less With Cast?

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    Default Bearing Friction less With Cast?

    I guess this may be a true/false question, not sure.

    I was questioning a reloader about his 45/70 loads using Cast Performance 470gn. He is using 47 to 48 grns of RL-7. My thinking was this would easily put him in the 70,000 to 80,000 psi range. His response was that using either Cast Performance or Performance Cast (different companies, same bullet) there is less bearing friction with lead cast so loads can be increased with while still keeping pressure manageable.

    I can Partially see how this might be similar to having graphite lube on a bullet but with hard cast would it be the same?

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    Quote Originally Posted by TYBSP View Post
    I guess this may be a true/false question, not sure.

    I was questioning a reloader about his 45/70 loads using Cast Performance 470gn. He is using 47 to 48 grns of RL-7. My thinking was this would easily put him in the 70,000 to 80,000 psi range. His response was that using either Cast Performance or Performance Cast (different companies, same bullet) there is less bearing friction with lead cast so loads can be increased with while still keeping pressure manageable.

    I can Partially see how this might be similar to having graphite lube on a bullet but with hard cast would it be the same?

    Two things here. First the big thing.....I'm pretty sure a charge of 48.0 grains of RL-7 and a 470 grain bullet in a 45-70 will yield 70,000 psi. Even with a jacketed bullet. Was that a program or just a guess? I would say it is about 45,000 psi. It is in several loading manuals as a safe load. So fear not.

    Secondly...I agree with the lower friction but with qualification.
    When loading two bullets of the same weight, one jacketed, one cast, in the 45-70 (or any caliber) with the same powder charge, the cast bullet will be faster. BUT and this is a big one. You could also get higher velocity from one of two bullets of equal weight when both are jacketed. And that could be due to higher pressure. It could be from higher pressure with the cast, also.

    Bearing surface, friction, diameter and the amount of crimp all affect the pressure, which changes the velocity. Increasing any of these will increase pressure but not necessarily the velocity. Think of friction, being greater would offer more resistance to the accelleration of the bullet, increasing pressure, but would be drag on the velocity curve. Crimp increases the "rate of confinement" and ups pressure and usually velocity. We can and usually do crimp lead bullets more. So other factors apply here but I do believe that a cast bullet will give higher velocity at the same pressure, or the same velocity at lower pressure. And all loading date published by major makers support this conclusion in data numbers though I don't remember ever seeing the verbage in print.

    I have loaded jacketed and cast bullets in rifle and handgun and shot them through the chronograph for a solid 30 years since I made my first chronograph back in the seventies. I have drawn a few conclusions about certain things and I'm sure some of them are correct.
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    So no one here has bought one of those fancy piezio pressure rigs?

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    Quote Originally Posted by Murphy View Post
    Two things here. First the big thing.....I'm pretty sure a charge of 48.0 grains of RL-7 and a 470 grain bullet in a 45-70 will yield 70,000 psi. Even with a jacketed bullet. Was that a program or just a guess? I would say it is about 45,000 psi. It is in several loading manuals as a safe load. So fear not.

    The pressure was basically a guess. I've got 4 load manuals and none show a 470gn load. Though Hornady shows their 500gn jacketed using a max load of 44.5gns of RL-7. Nosler doesnt show anything close. Speer shows a 400gn max load of 48gns of RL-7 but that is far from 470gns.

    I personally went to 46.5 gns and got 1610 through my BFR Revolver and am told that 47 gns will produce 1900 from a marlin. (Both Chronographed) I backed back down to a Max of 43 gns (Chronographed at 1424) for my revolver due to recoil but I'm not sure about a rifle round.(Marlin Lever)

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    Quote Originally Posted by Beer:30 View Post
    So no one here has bought one of those fancy piezio pressure rigs?




    I have an Oehler model 43 system. It uses a strain gage as a "pressure transducer" that you epoxy to the barrel (chamber) . It is then connected to a PC (laptop) and will display pressure curves, etc. This isn't the best system and requires precise measurement of chamber wall thickness and some standard ammo for calibration runs. I have a lot of pressure numbers from it that seem to support most manuals.

    The Load from a Disk S/W is also a very informative program and I've used it a lot too. It does not rely on a set of "standards" of dimension just case volume, bore size, swept barrel, etc. basically just what you can easily measure. Lots of gadgetry.
    Is there nothing so sacred on this earth that you aren't willing to kill or die for?



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    Quote Originally Posted by TYBSP View Post
    The pressure was basically a guess. I've got 4 load manuals and none show a 470gn load. Though Hornady shows their 500gn jacketed using a max load of 44.5gns of RL-7. Nosler doesnt show anything close. Speer shows a 400gn max load of 48gns of RL-7 but that is far from 470gns.

    I personally went to 46.5 gns and got 1610 through my BFR Revolver and am told that 47 gns will produce 1900 from a marlin. (Both Chronographed) I backed back down to a Max of 43 gns (Chronographed at 1424) for my revolver due to recoil but I'm not sure about a rifle round.(Marlin Lever)
    What barrel length is on the BFR? The limiting factor is probably going to be recoil. Do you have trouble with bullets backing out of the case with recoil? For its effectiveness, there is really no reason to go above 1400 fps and actually anything above 1100 fps or do all that can be done with that load. That is some pretty serious velocity for such a big bullet.
    Is there nothing so sacred on this earth that you aren't willing to kill or die for?



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    Quote Originally Posted by Murphy View Post
    What barrel length is on the BFR? The limiting factor is probably going to be recoil. Do you have trouble with bullets backing out of the case with recoil? For its effectiveness, there is really no reason to go above 1400 fps and actually anything above 1100 fps or do all that can be done with that load. That is some pretty serious velocity for such a big bullet.

    My BFR has a 7.5" barrel and your dang correct about recoil being the limit. I recently bought it and my first order of business was to find out where manageable recoil was. 1610fps does not produce manageable recoil.....hehe. In fact it hurts not a little to pull the trigger thus making accuracy nearly impossible. Around 1400 recoil is significant but I'm used to my 454 and 500 Smith so its not too much. I crimp tightly and have not had any jump crimp even at 1610fps.

    My concern was more for my Marlin. With the BFR, recoil definetely is the limit but not so with my Marlin though it too will kick like a mule. Its a second year production model and has a nice curved Butt pad made of 1/4" steel.

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    Gotta like those solid butt plates... Reminds me of the Remington Model 6 that I used to have ...a pump action .30-06 believe it or not. That gun was an accurate shooter though. My first experience with it was in an indoor range, shooting from a shooting table that was just plain too low for my 6'3" frame. I thought, "Hmmm... no recoil pad, just a solid plastic plate. Well, it's just one shooting session." After leaning forward too far and having that gun kick me in the shoulder bones about 40 times, I could no longer lift my arm and nearly couldn't drive home because my right arm was so hard to raise for shifting the standard transmission in my car ...Didn't seem so bad when shooting, but man did I figure it out afterwards! . About a week after that, that gun had a Decelerator on it... heh heh. Night and day difference.

    Brian

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