Just as a matter of possible interest to some, I made up a dozen each loads consisting of 158 grain bullets (lead SWC and FMJ) in .357 Magnum cases, using 7.0 grains of Unique (weighed), with maximum COAL. In firing, I used my pristine Colt .357 Trooper with a 4" barrel. Cases had mixed headstamps, and I used all chambers, to simulate reality. I chronographed these loads, and dropped the maximum and minimum MVs for each, leaving a 10 shot group for each to perform statistical analysis.

1. 158 grain lead SWC: Average MV = 1103 ft/sec, SD = 38.3 ft/sec

2. 158 grain FMJ: Average MV = 1016 ft/sec, SD = 18.4 ft/sec

Therefore, for this load, the MV difference is 87 ft/sec, in favor of the lead bullet. I am surprised the SD was so much greater for it vs. the FMJ.

You really shouldn't be.. lead has a sort of lubricating quality to it. I can't explain it, but it is a fact. Additionally, lead is softer than copper, and as a result there is less friction. Less friction means higher velocities, at least in my mind.

Cast = higher velocity for any given powder weight over jacketed.

Kinda why I like cast.

Yup! I have posted numerous times that on average the velocity difference between a cast bullet and a jacketed one is 100 FPS +/-. It always favors the Lead bullet. You are right there! This isn't guessing, it's a result of chronographing literally thousands of rounds.

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Gunsmithing since 1961

Many say this but think about it, if the bullet was slicker, vel would be less. You see this in moly coated bullets, less vel with identical charge wts. I believe it is the softer alloy creating higher friction thru greater bore seal, higher pressure & then higher vel. More maleable yes, but slicker, not really. Some day I'll have a pressure trace & can prove this.

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NRA Cert. Inst. IDPA CSO

I also suspect that Colt 3-5-7 has a pretty tight bore which tends to raise pressure and velocity. Or put another way...a worn bore will tend to give lower velocities than a tight new bore. Pythons are rather famous for tight bores.

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Bob.
SWCA 1821

If that were true then why wouldn't plated bullets be as fast or faster than lead? They have soft cores (most brands) and only a thin plate of copper, so they should fill the bore and seal like lead. But they always test slow like jacketed.
I think (guess) that pressures are similar in all the loads and the lower friction bullets like lubed lead and powder coated lead gain more velocity. Copper has high friction, whether it's thinly plated over a soft core or in a heavy jacket, so it's slower.

Lead is a lubricate all by itself.

Less friction ='s more velocity

I've tested jacketed, lead with traditional lube & powder coated bullets by swaging my own bullets with the same shape/design for the 35cal's, 44cal's and 30cal's.

In every test the powder coated bullets had the highest velocities. Followed by traditional cast/lubed lead bullets and then jacketed.

Well they are faster than jacketed, hence my theory it is a better bore seal increasing pressures. Again, lower friction bullets do NOT gain vel. Look at the Barnes manual. They have data for identical bullets but foe their moly coating. The slicker buckets require more powder to achieve the same vel. Less friction, lower pressure. I suspect using bullets 0.001-0.002" larger also increases bore seal & raises pressures. It is my theory, based on available data & my own vel testing. Without pressure data, hard to prove, but the slicker bullet theory has already been debunked in the Barnes manual.

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NRA Cert. Inst. IDPA CSO

My own exp as well, but by coating you remove the mythical lubrication of lead. Again, review the Barnes data, slicker bullets need more powder to achieve the same pressure/vel levels. Only pressure testing would prove it either way.

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NRA Cert. Inst. IDPA CSO

Bringing plain vs moly rifle bullets into this add pears and tangerines to the apples vs oranges in handguns.

Digging into info back when molly was new , the slickness of molly created issues with bullet pull ( aka effective case neck tension) in magnum revolvers.

Cast bullets can have multiple variables in themselves , but if we stipulate that the hardness and sizing is reasonably suitable for the gun and load in question, the reduced bore friction will make a difference.either higher vel at same pressure , or same vels at lower pressure.

This makes no sense to me.......a slicker projectile HAS to be faster from decreased resistance. Resistance does NOT increase velocity by raising pressures!

I don't have the Barnes manual, but it sounds like ballistic hokum from here. Maybe moly is a law unto itself, but you'll never convince me that a powder's burn rate and pressure curve is determined by what coating is on the bullet.

It might affect it to a small degree, but it doesn't control it.

If by 'they' you mean plated, they test the slowest of all bullet types according to these tests in auto pistols.
How Fast is your Bullet?

OTOH, this article about moly seems to agree with your side.
http://www.midwayusa.com/general.mvc...harts~moly-faq

Maybe it's more complicated than I think.

I totally appreciate papajohn's struggle with the idea that moly-coated bullets show decreased velocity, assuming all other factors are constant. It boggled my mind too when a friend and I first discovered it back in the 90's.

We were very active in USPSA shooting and experimented with moly-coated cast bullets from the Bull-X company(RIP). We loaded the same bullets(cast/lubed vs. moly-coated) from Bull-X with identical components and powder charges, brass, primers and fired them over chronographs. We used at least two different chronos to make sure the readings were similar. We ended up totally convinced the moly bullets went slower. Since that meant we had to use more powder to make major we gave up on moly. Moly residue in a gun barrel attracts moisture and the disulfide causes rust. We learned that when we found rust running out of gun barrels left uncleaned.

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Bob.
SWCA 1821

Moly coated bullets and powder coated bullets are light years apart, like not in the same zip-code.

They shouldn't even be in the same sentence when comparing bullets!!!!

It doesn't matter if the powder coated bullet is left a soft alloy, or water dropped to harden them or heat treated and aged to harden them.

They have the highest velocity across the board.

It doesn't matter if the copper coated bullet is left a soft alloy, or water dropped to harden them or heat treated and aged to harden them.

They will always be slower than traditional lead/lubed bullets and pc'd bullets.

Moly does what it is designed to do, prevent parts (bbl/bullet) from sticking/seizing together. Hence no seal ='s gas leak or lower pressure due to the lack of a bbl/bullet fit/seal.

Powder coating on the other hand was never designed as a lubricant, it was designed as a protective coating. It just happens to do an excellent job as a bullet lube.

Barnes isn't the "holy grail" or the last word on bullets and bullet lubes. And actually quoting 10+ year old data from them does nothing for modern tests, bullets, lubes or bullet coatings.

1000's of shooters have done tests and keep coming up with the same results. Lead lubricates better than copper and pc lubricates better than traditional lubes/lead.

Both copper jacket and lead seal the bore as well so the pressure will be very similar.

Lead bullets have less "pull" resistance in the bore, hence the higher velocity for the same pressure. Lead bullets are lubed so that the bullet has a lubricant between the lead metal of the bullet and the steel bore to minimize lead contact. No lubricant and you get lots of lead depositing in the barrel.

Lead most certainly does NOT lubricate better than copper
Coefficients Of Friction

Dynamic friction/sliding friction is what we care about.

Lead on steel = 1.4

Copper on steel = 0.8

We know powder requires pressure to burn, more friction = different pressure curve, which can mean better combustion of powder. Take a look a max loads, lead will often hit the max pressure before a jacketed bullet of the same weight.

If you've chrono'd coated (be it moly, tungsten, or boron) rifle bullets you'd see a very noticeable drop in velocity just from coating. How do we explain that? Change in pressure curves = changes in the powder burn efficiency.

Think of it this way. Powder burns & creates pressure to push the bullet. Reduce the pressure generally reduces the vel, all things being eq in the load. Again jacketed moly shows a reduction in vel. Moly coated lead shows a slight reduction or no loss of vel for identical loads. Look at it mother way. Shoot an undersized bullet, friction is less but so is pressure & vel. Just food for thought, but doing a bit of study, a slicker bullet is rarely faster in the bore. My theory, believe It or not, don care, it is my theory. At least i offer a vlid explanation, not just hyperbole. Someday I will have the pressure trace to prove or disprove.

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NRA Cert. Inst. IDPA CSO

Good stuff, learned a lot.
I guess I always assumed lead was slicker than copper.

More malleable, not slicker. Many assume because you can more easily drive one thru a bbl with a rod that it is slicker, but it is just more malleable.

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NRA Cert. Inst. IDPA CSO

The higher SD seen with lead over jacketed bullets observed in your
test does seem surprising. My first thought would be that you didn't
use much of a crimp with the lead bullets and their lower coefficient
of friction creates a need for the resistance of a good crimp for
consistant initial movement out of the case.

The friction isn't less though, this just keeps getting thrown around, it's not less friction. THe diff in SD is the springback of the brass when crimping. The lead compresses slightly, the brass springs back, neck tension then varies. Annealing cases would help, crimp, too much can make it worse.

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NRA Cert. Inst. IDPA CSO

When lead SWCs are the bullet involved I think of the typical
designs that feature a crimp groove. A substantial roll crimp
over the shoulder of the crimp groove has been shown to
increase velocity and contribute to efficient powder burning
in loads whether light or heavy. I don't think there's much
"spring back" of the case mouth when roll crimped into a
groove. If there is it's certainly not visible to the naked eye
in any loads I've ever assembled with cast SWCs. Some
folks want to taper crimp loads with lead bullets for some
reason, maybe your theory would apply to their loads. But I
don't know how anyone could conclude that there's no
difference in friction between lead and jacketed bullets.Try
driving one of each through a barrel with a hammer and
brass rod and see how that works out. Ever see anyone use
a jacketed bullet in a muzzle loading rifle without using a
sabot? I haven't either.

If a lead bullet gets a higher velocity with the same amount of powder with less pressure, it stands to reason that lead bullets could take a somewhat higher load of powder and get the highest velocity attainable out of a gun.

I'M NOT ADVOCATING EXCEEDING PUBLISHED LOADS, just proposing a reason why lead bullets could get maximum velocity compared to any other bullet type. Call it a physics puzzle.

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"He was kinda funny lookin'"

I think your generalization seems sound. But in reality, there are many published lead bullet loads. So one doesn't need to start with jacketed data and then guess at how much of an increase (if any) can be safely had.

As an example, Lyman lists .44 Mag loads with 2400 that have similar pressure. A 240gr cast bullet with 20.6gr lists 1250 fps and 38,000 CUP. The two jacketed bullets they list of the same weight list 19.5-20.5 grains of powder, go 1150-1170 fps, and also reach basically 38,000 CUP.

There are probably counter-examples out there as well. And of course many lead loads that are artificially light so that the bullet itself doesn't fail.

I am all for velocity, but the differences in jacketed, plated, lead, etc don't seem extreme to me. I like some other purported aspects of lead, like reduced wear on the barrel. Personally though I find plated or jacketed "simpler" to shoot in revolvers. I don't have to measure throats or barrels or bullets to get decent performance. And the cost of plated and lead are about the same (unless you make your own). I'm not into it enough, I suppose. Mostly I reload for the cost savings.

Problem is that jacketed bullets can be driven to somewhat higher velocities than lead bullets, depending somewhat on the lead alloy and lubricant used, and whether gas-checked or not.

Well spoken!!!!

The real issue is that (this thread is an excellent example) most people can't wrap their noodle around the fact that there's a huge difference between what happens to lead and copper when such a minor thing as pressure is added to the mix.

Well let's see, in my hand this one's slicker than that one, yada/yada/yada.

Try adding a 10,000psi+ and see what happens. Hay!!! Wait a minute!!!! People already have & the chronograph don't lie.

You can lead a horse to water only to watch them drown.

Ken Waters of Handloader magazine did a test between 38 special and 357 mag chambered revolvers in 4" and 6" barrel lengths.

The end result was a 4" 357 magnum firing a jacketed bullet 38 special load versus firing a lead load in a 6" 38 amounted to almost 200 fps difference, favoring the 6" 38.

There were many results published for the test, powders, primers, bullets, etc. Lots of variables to consider.

Lots of variables indeed. I am very leery of believing any comparative MV results involving different revolvers. My own comparisons of MVs between my 14-3 (6" barrel) with my Colt 3-5-7 (also a 6" barrel) has shown that identical .38 Special loads produce OVER 100 ft/sec average MV differences, always in favor of the Colt. I think the Colt has a somewhat smaller cylinder-forcing cone gap (you can barely see daylight), but it could also involve barrel and chamber dimensions, forcing cone angles, or maybe other unknown factors.

No one said there is no diff in friction. Again, you mistake maleability with less friction. Even if you roll crimp, there is some next tension implied. That is where spring back can occur, especially if you over crimp even slightly & buckle the case even 0.001-0.002"

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NRA Cert. Inst. IDPA CSO

Cases were mixed head stamps; coupled with 2 different bullets = different case capacities. Use the same brass and trim it so you get a more consistent crimp. Seat the bullets so that they take up the same space in the case.