Please 'Splain This To Me: Lead VS. Jacketed Pressure

[GunAdmirer]

I think all the reading of reloading guides has finally gotten to me.

According to my Lyman manual, it seems that the powder charges for lead bullets is less than for the same weight of jacketed bullets. The pressures listed seem comparable. I know that the bullets are very different in construction and resistance.

Here's my questions:
If a lead and jacketed bullet were similar in construction and handloaded using the same powder charge and components, would the lead bullet generate greater pressure and velocity than the jacketed?

Does the lead bullet generate higher pressures with a lower powder charge because it seals better?

Can a lead bullet be driven to higher velocities (within safe pressures) using jacketed data if leading were not an issue?

Obviously, I am confused.

 

[AFhack]

"Here's my questions:
If a lead and jacketed bullet were similar in construction and handloaded using the same powder charge and components, would the lead bullet generate greater pressure and velocity than the jacketed?"


High pressure does not automatically convert to high velocity, especially when friction is vastly different between two different types of bullets. Generally speaking, it takes less pressure to push lead down a barrel than it does to push copper down a barrel. So, if you were to take exact same weights of bullets, one lead and one copper jacketed, and put them in front of the exact same powder charge, the lead one is going to exit the barrel faster than the copper jacketed one. The slower moving jacketed round will generate a higher pressure in the chamber just because of the fact that it's releasing (moving down the barrel) slower than the lead round the pressure has more time to build and less area to release into.

 

[Bullet]

I was told that lead will create higher pressures than jacketed because it makes a better seal or a faster seal.

I was at Hodgdon Powder Co awhile back talking to one of the guys there about bullet speeds and bullet composition and this is what he told me to the best of my recollection.

 

[Murphster]

I'm not an expert on this but I've always heard that with a jacketed bullet, some of the gas escapes past it in the grooves when the cartridge is fired. A lead bullet obturates more thus making a tighter seal preventing as much gas from escaping past it and creating higher pressures.

Or maybe not.

 

[Grump]

Can a lead bullet be driven to higher velocities (within safe pressures) using jacketed data if leading were not an issue?

IME, no. No leading issues with *some* Oregon Trail bullets and *some* Rim Rock hard-casts (both above 20-22 BHN) in *some* of my guns, but exceeding the jacketed bullet velocities always, without fail, showed higher pressure signs than those loads with jacketed bullets of equal weight.

I could equal them (within 30 fps either way, IIRC, at 1200 fps or higher) in .357 Magnum with 125-gr bullets, with 296 and Power Pistol, but exceeding those velocities never worked.

 

[triple4]

First off you should see higher velocities with hardcast bullets vs jacketed and the same charge of powder, why Hardcast bullets are by nature Slicker (lubricity) then add a little lube it helps as well. Hardcast can seal better if the powder charge/bullet hardness can obturate the bullet.

The Hardcast bullet also is by nature shorter then the same weight jacketed bullet so if possible you can have more powder space, so since its easier to get the bullet moving and keep it moving we develop a different dwell time at peak pressure vs jacketed the bigger the expasion ratio the less time at peak pressure.

 

[anonanon]

Since Hodgdon has been quoted, here's some data from them:
13 gr H4227 wi 158-160 Lead, 1223 f/s at 24800 CUP; 12.5 gr H4227 wi 160 gr Jacketed, 1172 f/s at 25800 CUP. 2.8 gr HP38 wi 158-160 Lead, 731 f/s at 9900 CUP; 3.2 gr HP38 813 f/s at 13300 CUP. Other powders, calibers, bullet weights -- when you can find comparable loads -- work out the same way: Lead gives more velocity and/or less pressure than jacketed. Obturation, lubricity, all the theories are interesting and no doubt valid, but empirical results show lead bullets are faster for the same pressures.

 

[Ol` Joe]

Since Hodgdon has been quoted, here's some data from them:
13 gr H4227 wi 158-160 Lead, 1223 f/s at 24800 CUP; 12.5 gr H4227 wi 160 gr Jacketed, 1172 f/s at 25800 CUP. 2.8 gr HP38 wi 158-160 Lead, 731 f/s at 9900 CUP; 3.2 gr HP38 813 f/s at 13300 CUP. Other powders, calibers, bullet weights -- when you can find comparable loads -- work out the same way: Lead gives more velocity and/or less pressure than jacketed. Obturation, lubricity, all the theories are interesting and no doubt valid, but empirical results show lead bullets are faster for the same pressures

Once more from Hodgdon..........

From Hodgdons Annual manual loads for the 45 acp and 44 mag useing the SAME powder charge and bullet wgt.


45acp 200 gr
lead; 8.2 gr HS-6 860 fps @14400 PSI
jacketed; 8.2 gr HS-6 868 fps @14000 PSI


45acp 230 gr
jacketed; 8.0 gr HS-6 790 fps @ 14400 CUP
lead; 8.0 gr HS-6 859 fps @ 16600 CUP

jacketed; 5.4 gr Universal 751 fps @13300 CUP
lead; 5.4 gr Universal 857 fps @16800 CUP

jacketed; 4.8 gr Titegroup 818 fps @16700 CUP
lead; 4.8 gr Titegroup 855 fps @17000 CUP



44mag 240 gr
lead; 11 gr HP-38 1334 fps @38100 psi
jacketed; 11 gr HP-38 1272 fps @37800 psi

lead; 10 gr Titegroup 1288 fps @ 38400 PSI
jacketed; 10 gr Titegroup 1292 fps @ 37700 PSI

lead; 10.2 gr Universal 1276 fps @ 37500 PSI
jacketed; 10.2 gr Universal 1247 fps @ 38200 PSI

One can never state that lead always is lower in pressure or gives higher velocity with the same powder charge, it`s only a "general" rule that`s wrong almost as often as right.

 

[triple4]

You are right, its not cut and dry, Crimp, throat size, bullet size,Powder, primers, all play a part........I once read a test were rubber bullets was used and only primers No powder and the spread was + - 200 fps.

 

[anonanon]

Ol' Joe, I stand corrected. You obviously did better and more complete research than I did. I had questions about some statements, gave a quick look at data, and saw what I wanted to see, without checking in depth.
Pretty much you covered it when you said one can never state that something is always true...and general rules are wrong almost as often as right.