All things being equal, does a jacketed bullet of same weight and caliber generate more pressure than a lead bullet?

I have read that a jacketed bullet is harder to engrave and requires more pressure compared to lead. Does this transfer into "Chamber" pressure?

I have compared plenty of Jacketed bullet data to same weight Lead data and there seems to be no direct correlation between bullet composition, powder charge and pressure. Some data will list more powder with the Lead bullet, some will list less and some will list the same. I am talking about from the same manual or powder distributor's data, not from one manual to the next.

I have also read that jacket bullets can produce less chamber pressure than lead, because a properly sized lead bullet seals off the bore and traps the gasses behind the bullet. A harder jacketed bullet does not seal the bore as well or as completely and gasses can escape past the bullet thus reducing "Chamber" pressure.

Is there even an answer to this question?

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.

Interesting, I would have thought it was the jacketed�.learn something new every day!

Same here, from having to drive bullets out of bores. Just goes to show ya, hadn't considered gas sealing.

I knew that watch out or you'll lose your Poobah card

Found this on another forum, what do ya think?

Lower pressures will be observed with lead bullets. Barrel friction isn't the principle reason. Copper jacket alloy has a higher static coefficient of friction with the brass case neck than a lubricated lead bullet does. Also, copper jacket alloy is substantially harder than lead, and, even though it is just a thin skin over a swaged lead alloy core, it takes more pressure to engrave a jacketed bullet with the rifling than a lead bullet requires. The combination of these factors results in higher start pressure and more powder burned getting a jacketed bullet started onto the rifling. Burning more powder before the bullet moves down the rifled portion of the barrel far enough to expand the volume behind it yields higher pressure. This is true for both rifle and pistol.

Nick

Yup. and your chrono will show that with like weight bullets and powder charges.

Here's somedata from Hodgdon's website:

.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.

I don't know who "Nick on another forum" is, but all he has to do is look at the vast amount of pressure-tested data available today to realize he's FOS.

For ships and giggles, I crunched the numbers for three 240 gr. 44 Magnum bullets. One by Lee and two by Hornady. I used 22.0 gr. of IMR 4227.

The two jacketed bullets were shorter in length.

.678 - Hornady HP (23,700 @ 1547 fps)
.710 - Hornady SWC (24,300 @ 1554 fps)
.735 - Lee cast SWC (26,200 @ 1573 fps)

.735 - Lee cast SWC (25,100 @ 1551 fps)

If you throttle back the velocity of the cast bullet, and bring the it in line with the jacketed bullets, the pressure is a tad higher, but not much. - 800 PSI more than the Hornady SWC and 1400 PSI compared to the jacketed HP.

Of course, this is a computer determined pressure projection. For me, it's not really much of a difference. Although, I grant that there is a little more with the lead.

Edited to add: With these same weight bullets, because the length changes (the lead bullet is longer), there is less internal space for the propellant. With the jacketed bullets, the 4227 occupies less than 100% capacity. For the cast bullet, it becomes a compressed load.

This is what I've always assumed since the jacket is generally harder than lead. Not too old to learn new tricks.

Recently, I did a work up in one of my 9.3x62 Husqvarna rifles using Northman 285 gr plain base cast bullets. They measure .368, and are twice-lubed using Alox.

The velocity was 2236 fps with a half inch square of old cotton towel wad, tamped down over the powder, and slightly compressed COW filler to base of bullet. Group with this load is 2.1 inches at 100 yards.

This bullet penetrated six four-litre jugs of water, and was caught in the seventh. That's over 36" of water and more than half an inch of plastic!



You can see how cleanly the bullet is engraved by the rifling. Note, as well, how near perfect the base of the bullet is. No fusion has taken place at all. The gas seal is quite secure.



Now, the point of all this is that the bullet is getting almost the same velocity as the same weight jacketed bullet USING FIVE GRAINS LESS POWDER. Evidently, the cast bullet load generates higher pressure. Enough that five grains less powder gets the same velocity.

Of course, one huge difference is the COW filler, which the jacketed bullet load did not use.


Interesting stuff,
Ted

If we go back about 150 years, the military determined the need for jacketed bullets was absolute, thanks to the introduction of smokeless powder. Because it launched bullets significantly faster than BP, European military developers knew they had to figure out a way to stop lead smearing. A (rare) tip of the hat should go to Paul Vieille (inventor of smokeless powder - France) and Swiss army officer Eduard Rubin (inventor of the bullet jacket).

What we have to remember is that the military set the standard back then. They did over 90% of the research and experimentation with firearms cartridges. As a result, jacketed bullets were here to stay. It didn't take long for new cartridges and jacketed bullets to find their way over to the civilian world.

Shooters have been reloading for many years with jacketed bullets. As a result, many have forgotten how to load lead. Fewer people have that basic knowledge. Most reloaders are scared that using lead bullets is dangerous, restrictive or too complicated.

Many believe that they will line their bores with lead, accuracy will decline, or both. Some are even scared that their firearms will blow up when the bore becomes clogged up and internal pressures will go through the roof.

Does a gas-checked cast differ greatly from one that isn't?

If one bullet is easier to move down the bore than another, then wouldn't the bullet that is easier to move have a potentially greater velocity at the same pressure?

This is, in part, what fans of molly believe, correct? This is also why equal weight bullets with greatly different bearing surfaces can not use the same max load data.

I thought cast bullets moved through the bore with less friction than jacketed (or at least were far easier to drive down the bore) that therefore they achieved equal velocities with lower powder charges.

My experience with cast bullets is limited to pistol rounds and the 45/70, but it is true that equal powder charges will produce higher velocity with the same weight bullet in those cartridges when comparing cast to jacketed.

Since one can drive a lead bullet down the bore with a mallet and brass rod and cannot readily do the same with a jacketed bullet -I believed the lead bullet must have less friction associated with it. Is this not true?

In long guns, you have to watch the pressure and lead hardness. Gas checks let you push the bullet faster, which means higher pressure, before they start to lead.

A general rule of thumb is 1000 fps max. for lead bullets and 2000 fps max. for GC bullets. You can start playing around with these numbers by varying bullet diameter, hardness and bullet style. Most of the lead that I shoot from my 303s, 30-30s, 45-70s and 44 Magnum is GC.

I use heavier bullets, so I do not have to worry about exceeding a self imposed limit of 2000 fps. Other shooters will tell you that they routinely exceed 2000 fps with their cast loads, but I don't bother.

Thanks - good stuff. Does a g-c cast bullet develop appreciably either more or less pressure with a given charge than does a non-checked one?

To be honest, I don't know. I cannot see there being much difference between the two. It's mostly lead riding the bore for both.

I just did a bunch of shooting with cast .22 caliber bullets designed for gas-checks. The alloy was a bunch of wheelweight metal I melted down and mixed together several years ago.

The bullets were all lubed with Lee Alox, but some were sized to .224" with gas-checks added, some were size without gas-checks, and some were left unsized and averaged .225" in diameter. All were loaded in the same brand of .22 Hornet cases with the same primer and powder charge.

The lowest velocity, by far, was with the gas-checked/sized bullets. The highest was with the unsized bullets, but the sized but not gas-checked bullets were very close.

The best accuracy was with the unsized bullets. They averaged about an inch at 50 yards, versus about 1.5" for the sized bullets, with or without gas-checks.

Another of those infamous examples of one.

Pressure aside, for cast bullet accuracy a somewhat soft bullet unsized with a diameter of groove or slightly (.001) larger diameter usually works pretty well.

I have to wonder about bearing surface, lead bullets are not streamlined so as a generalization I would expect modern spitzer jacketed bullets would have less surface area in contact with the barrel.

Very difficult to compare apples to apples in this hobby.

65x54,

That's been my experience as well.

My guess is that a lot of new bullet casters have mediocre luck because they assume all cast bullets must be sized. I cast for several of my rifles and handguns, and in most unsized bullets shoot more accurately. Of course, sometimes I try different lead alloys to see which works best, but in general I prefer doing as little work as possible!

Except that most Lead bullets are equipped with Lube grooves which take away from the actual bearing surface.

There is another consideration I think: Obturation.

Those extra few msec that result from the pressure building and pushing on the bullet before it moves. There's likely more hang time with lead than with a jacketed bullet.

I assume you mean the bullet is spending some time expanding (increasing dia.) instead of moving forward? Get your stop watch out and get back to us on that...


MD, and the trap for new casters seems to be as they lead their barrel they figure they need harder bullets.

How about I get back to you right now about that?

I have a couple of computer programs that plot the time spent in the barrel from ignition to exit. You can go with the powder company info or introduce your own information from a strain gauge.

I believe the higher pressure results from the lead obturating and spending more time in the barrel. The lead is more elastic. That allows the pressure to build slightly, as compared to a jacketed bullet.

I'm sure the surface of a lead bullet also results in more friction than copper or gilding metal.

Steve, it could be on the more barrel time thing. However there is no elasticity to lead. It's going to depend on the burn rate of the powder also as to just how much obturation there will be.

Interesting stuff that has a lot of time spent on it before this conversation.

Yes, lead likely has a higher coefficient of friction. This, and its elastic properties would explain the longer barrel time for the lead.

Lots of variables, lots of ifs and buts.

I've miked jacketed pistol bullets that obturate and quite a few rifle bullets do at rifle pressures.

One is also forewarned that at very low pressures jacketed bullets stick in bores much more easily; at higher pressures beyond a lead alloy holding its shape, the lead certainly will create more pressure and if its leading at that point, its pretty unsafe!

Everything exhibits elastic properties. WRT gun barrels, you have a cylinder upon which which the propellant acts. As the pressure increases, the lead compresses slightly. The time it takes to initiate the pressure, until it is sufficient for the lead to move down the barrel would be the barrel time.

From the time the pressure starts until the lead begins to obturate, would be its modulus of elasticity. This would be different for lead and jackets bullets. And, I suspect, different for jackets made from different materials.

Steve,

Lead isn't elastic, since that means returning to the original shape after stretching or deforming due to applied force. Lead is very malleable, however. As Hawk1 notes, even lead-cored jacketed bullets can deform under pressure.

That "elastic" property is more like a deformation; it takes the shape and doesn't return. The same thing happens when the nose hits something; it deforms by force and pressure.

I mistyped, and will try again.

Lead takes longer to move because it has a higher coefficient of friction. It also a low modulus of elasticity, so it will deform more quickly. (All metals have elastic properties. Lead has a low modulus. Elastic properties include both stretching and compression of a material before deformation.)

Because lead is softer and deforms sooner under pressure, it will take longer to move down the barrel. Like pushing Jell-O through a hose, or poking the Pillsbury dough boy before knocking him over. This slightly longer barrel time will allow a higher build up of pressure.

That's not always true though.

Heat treated lead alloys can exhibit zero obturation while a jacketed bullet can still obturate at the same pressure.


I'm not arguing, I'm just adhering to the concept that there are so many variables that occupy this discussion. The extremes however, are pretty much facts.

When you heat treat though, you are changing the properties of the material.

I think that there may be three or four variables, but not too many. It's out of my area, but I had to deal with engineers, so this sort of conversation was a regular event.

The original question, "Does a jacketed bullet of same weight and caliber generate more pressure than a lead bullet?" was answered. I think that we were exploring the reason explain why. I don't think we'll get to the bottom of it here.

Aren't you changing properties when you alloy too?

And lube, plus the pressure the lube can withstand then the size (and in some cases shape) of the lube groove...the position of the lube groove in relation to the bullet base....

And heat. It increases friction.

This is from Buffalo Bores web site, "...Additionally, hard cast bullets create less friction inside the barrel than jacketed bullets and thus we are able to obtain significant velocity gains at lower pressures, than would be possible with jacketed bullets."

Sundles is a pretty savvy ammunition manufacturer.

I took some time and read through my Lyman 48 and Hornady #7, looking for any information on bullet composition and pressure. Hornady had nothing. Lyman 48 had a small paragraph in their, "Mystery of Pressure" section page 99.

It basically said bullets are not created equal and can have a huge affect on pressure. Length, bearing surface, bullet hardness and composition can all play a role in chamber pressure. Hard (jacketed) bullets can be sensitive to bore diameter and rifling style and cause higher pressure.

It went on to say, Don't assume any rule of thumb to be true, especially this one. Sometimes a "hard" bullet shows lower pressure while the softer bullet shows higher pressure. A soft bullet may cause higher pressure because the bullet is so malleable that the sides will push hard against the bore when high pressure is exerted on the base.

I got this from Western powders.

Steve,
Lead bullets are generally longer than jacketed bullets, thus using up more case capacity, which in turn increases pressure. Lead bullets usually take less powder to reach max pressure, but generate more velocity than jacketed bullets.


Don W.
CSR Western Powders
406-234-0422

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."
_________________________
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.....