J-word vs Lead boolit powder charge questions.

Ok I have been reloading for a long time but just recently got into casting for my 9mm and 45acp. I have three loading manuals here and they all state lower powder charges for cast boolits than J-word bullets. This does not make sense to me. It would seem to me that a J-word bullet would create more pressure to swage into the bore than a cast boolit because of the copper jacket being harder than lead. Am I wrong? So my real question is, why is it that load data for cast boolits have published lower powder charges than there J-word equivalent?

Thanks,
Mark

Mainly because lead has a lower coeficent of friction than gliding metal used for jackets. The lead will slide easier down the barrel than the gliding metal jacket.

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Originally Posted by Zymurgy50

Mainly because lead has a lower coeficent of friction than gliding metal used for jackets. The lead will slide easier down the barrel than the gliding metal jacket.

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So if that is true. Shouldn't you be able to put a larger powder charge behind a lead boolit?

you answered your own question LIGHTS. it be the pressure thing. it takes more power to push jacketed then a lead boolit. also takes ...[in some cases]... less power to push a lubed paperpatched boolit then a bare lead boolit.

so the powder requirement in a row from most needed to least is;

1- jacketed
2- lead
3- lubed paperpatched

also you will notice that the powder speed is usually different in these applications. some powders interchange nicely such as the IMR3031 and 4064 and the RL-7 powders as well as unique.

OK, I understand that and that is exactly what I was thinking. I have been comparing apples to apples as far as powder and bullet weight. So most loading manuals are full of s^*t on their published max loads for lead boolits.

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Originally Posted by Lights

So most loading manuals are full of s^*t on their published max loads for lead boolits.

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Give the man a cigar............

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So most loading manuals are full of s^*t on their published max loads for lead boolits.

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Pressure and velocity are two different things, and not as linear a relationship as we might think.

While it's often true that the many published cast loads are not at SAAMI max pressure, they might be at a velocity limit for THEIR bullet. I'm thinking about some of the soft swedged bullets Speer and Hornady made. Their bullet alloy, hardness, fit, and lube are likely not the same as your home cast boolits.

If their bullet becomes inaccurate, leads, or otherwise performs poorly above XXX velocity, there's no reason for them to publish a load for that.

Most reloading manuals stop lead bullet testing when groups start to open up, or they start to get leading. Yes, you can drive a pure lead slug at 1800fps out of your 357 revolver. the question is: do you really want to?

sides that how many bullets are you gonna sell if the home made ones make them look bad by producing higher velocity's [velocity sells product]

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Originally Posted by Zymurgy50

Most reloading manuals stop lead bullet testing when groups start to open up, or they start to get leading. Yes, you can drive a pure lead slug at 1800fps out of your 357 revolver. the question is: do you really want to?

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That's not a good comparison, as the scenario is so far fetched. The point he is making is that if 'X' amount of powder 'Y' is the proper load for a 200gr j-bo in a .45acp, then why wouldn't that same load be appropriate for a boolit? I use the j-bo chart for my lead slugs in various pistols, and have had no problems with accuracy, feeding, and NO signs of overpressure. Of course, these are all modern guns made of modern steel. I would not do this in one of my turn of the 20th century top break revolters. And in rifles, that is a whole nother question. But with pistols, yeah, it's okay. :D

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Originally Posted by Lights

OK, I understand that and that is exactly what I was thinking. I have been comparing apples to apples as far as powder and bullet weight. So most loading manuals are full of s^*t on their published max loads for lead boolits.

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Well, yeah, sorta. Thing is the faster you push cast the more important all the little factors become. Fit, dynamic fit, at 750 or 850 or 1500 fps is different than at 900, 1050 or 2500. Sometimes bad things, real bad things happen when you decide to push that boolit out with a whole big ol' bunch o'powder. So, if you want to pick the pace up move slowly and OBSERVE what happens. Write it down and when you start changing things like luube, diamter, alloy, BHN, seating depth, etc. only change one thing at a time. Sometimes you get real lucky and your chosen gun/boolit/powder mix works just dandy, other times you spend a lot of time with a cleaning rod and 4/0 steel wool cleaning that sewer pipe full of lead that used to be a nice, clean barrel.

Anyone posting here ever do A/B testing of similar-weight and shape boolits and J-Words which included velocities?

Back when avoiding a kB! event in .40 S&W pistols was a great concern, I studied the Winchester reloading guide in some detail because it was one of the few that included pressures in the tables of data and estimated velocities for their loads.

What I found was that, leaving out obviously "short range" mouse phart loads, the W-W published max charges using the same powder and jacketed and lead bullets of the same weight, there were differences in charges, in a range of up to either 5 or 7% lower for lead getting almost identical velocity, on down to a minimum of zero (identical max charges, though the velocities were a little bit different if charges were identical or .1 gr different.

I also concluded that seeing a "max" load's PRESSURE for one bullet being a few thousand PSI or CUP lower than the other near-identical weight bullet might be because other variables between the two bullets made one more likely to "spike" the pressure or become inconsistent at only .1 gr more.

So I'd be careful with the rules suggested above.

I re-read the OP a couple of times to try to figure out what the point was and I still don't know for sure. I just looked at 45 ACP data in a Lyman manual and I don't see the discrepancy as portrayed in the OP. Am I missing something?

200 gr Jacketed
BE, 3.4 gr, 604 fps, 7100 CUP..........BE, 5.7 gr, 942 fps, 17800 CUP

200 gr Cast
BE, 3.5 gr, 645 fps, 6900 CUP..........BE, 5.6 gr, 869 fps, 15700 CUP

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200 gr Jacketed
700X, 3.3 gr, 597 fps, 7400 CUP.....700X, 4.9 gr, 871 fps, 17300 CUP

200 gr Cast
700X, 4.0 gr, 745 fps, 10300 CUP...700X, 5.2 gr, 940 fps, 17300 CUP