MV of cast vs. Jacketed bullets

[alwslate]

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.

 

[fredj338]

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.

 

[alwslate]

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.

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.

 

[rwsmith]

You know, if a lead bullet......

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.

 

[aurora40]

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.

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.

 

[DWalt]

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.

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.

 

[Forrest r]

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.

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.

 

[30calflash]

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.

 

[DWalt]

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.

 

[fredj338]

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.

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"

 

[azjohn]

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.