Home Forums Hunting & Shooting Ask The Gunwriters Jacketed vs Lead vs Pressure?

That is my experience as per my post #8565918 earlier in this thread.

It took five grains less powder to get the same velocity with cast bullets, as I got with jacketed of the same weight.

Ted

I didn't read this thread for a while because I thought it would be boring, and I thought I already understood the differences between lead and jacketed. Apparently, I didn't understand it anywhere near as well as thought, and now I'm really glad I read the thread.

It has been printed many times by respected authors that cast bullets produce higher velocity than jacketed, and many times that statement goes on to say "with lower pressures." Indeed, the Sundles quote above says thus as I understand it. This leads one to believe lead bullets have magical properties. I have read that for years and thought I understood the concept. Now this thread comes up and contains statements by respected authorities that claim basically the opposite. What's a layman to think?

What's a layman to think?

When the layman is a dummy like me, he does better not to think too much.

I agree though, it has been one of the better threads of late.

One pressure "problem" is we tend to discuss the peak pressure and not the area under the curve which is a more complete picture of the power available to get the bullet moving.

The smart ones will think that there are too many variables involved to get a good answer to this sort of question.

Ballistics isn't an "absolute" science

At best it's just educated predictions

It is an absolute science. It just requires equipment that most people don't have at their disposal.

.44 Magnum handgun--
240 cast/ 22.0 IMR4227/ 33,300 CUP
240 jacketed/ 22.0 IMR4227/ 28,400 CUP

.38-55 rifle--
250 cast/ 27.0 H322/ 27,000 CUP
255 jacketed/ 27.0 H322/ 25,500 CUP

250 cast/ 24.0 IMR498/ 36,200 CUP
255 jacketed/ 24.0 IMR4198/ 31,400 CUP

Please not that even though the jacketed bullet in the .38-55 weighs 5 grains more, pressures are less with the same powders charges. And in all the above instances, the STARTING load with jacketed bullets is the MAX load with cast bullets.



Just a guess - but I would think the only way this data would be valid as a comparison between lead and jacketed is if the bullet shapes were exactly the same. Or am I missing something?

It's results are only "absolute" for the test that was done and recorded

It doesn't mean it can be duplicated precisely in another firearm

Even "identical" loads in the same gun will quite often give varying results

If it were truly "absolute" you could always duplicate loads exactly

Math is "absolute"
Ballistics........not so much

Whatever you want to believe.

I believe reality.

It's a simple fact that X amount of powder under Y bullet will produce DIFFERENT amounts of pressure in different guns, or even in the SAME gun if more than one round is fired

That's why there's such a thing as "Standard Deviation"

Even the most consistant handloads won't produce the exact same velocity for every round, as it would if the science was truly "absolute"

So, are you disagreeing with this comment?

"Normally a lead bullet of the correct diameter and hardness produces more pressure with the same powder charge, because it does seal the bore better."
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John

There's no reason to disagree since it's not an "absloute" statement, as evidenced by the first word in the sentence

It also spells out two specific parameters that have to be met for it to be true.

With standard deviations, it's still possible an individual load could randomly produce more pressure with a jacketed bullet

I also think there are more factors involved than just how well a bullet "seals the bore" since all properly sized bullets are swaged to fit the barrel on firing

Interesting.... i had thought that the lead bullet = < pressure thing was along the lines of the sun is probably going to rise in the East......

Since we are talking cast bullets..... I had also thought that it is difficult to cast an accurate .22 bullet...... I have a CZ in .221 Fireball..... Might need to look into trying cast in it.....

I don't think I have ever seen commercially cast .224 bullets though..... ? The CZ loves 40 grain Vmax bullets..... Thinking it likely has a slower twist.....

http://www.moyerscastbullets.com/pricelist.html

Okay they are out there.....