Lead vs Jacketed load data

[pantannojack]

I just read the thread about Alliant 2400 vs hercules 2400, with various primers resulting in differing pressures. It refreshed in my mind my question regarding how most printed manuals recommend lower charge levels when using lead bullets compared to jacketed ones.I savy the possibility of leading and progressively increasing pressure as leading worsens, but wonder does the possibility of the lead projectile increasing in diameter under pressure increase resistance in bbl travel? I am casting 158g Lee gas check bullets sized .357 from whatever mixture I have in the pot lubed with some red stuff requiring about 100 deg. Never pure lead but some WW, some lino, some salvage with tin added. I like the HS 7 @ 10g as recommended by Hodgdon but with F100 std primer, and 15g IMR 4227 also std primer. My loads are not showing any bbl leading at all.

 

[WR Moore]

IIRC, the difference in charge levels have to do with flame temperature that might produce leading. Also, lead (and plated) bullets are generally easier to drive down the bore than jacketed. The load manuals generally are approximating factory velocity levels, not going where no (sane) reloader has gone before.

 

[mtgianni]

Some of the manuals are using swedged bullets rather than cast. Frequently the Lyman Handbooks show higher charges for cast than jacketed as there is less friction moving sown the bbl. Less friction also results in less pressure so the amount of powder is increased, increasing speed and resistance from friction.
Not all manuals due this, some because of their ballasticians, some because of the marketing of cast projectiles they are not selling.

I am not sure about flame temps and leading. I have experimented by putting a dab of grease on bullet bases before loading and firing. The grease is still present on the bullet when it's recovered. If it won't melt grease I have a hard time believing it is melting lead.

 

[rockquarry]

I just read the thread about Alliant 2400 vs hercules 2400, with various primers resulting in differing pressures. It refreshed in my mind my question regarding how most printed manuals recommend lower charge levels when using lead bullets compared to jacketed ones.I savy the possibility of leading and progressively increasing pressure as leading worsens, but wonder does the possibility of the lead projectile increasing in diameter under pressure increase resistance in bbl travel? I am casting 158g Lee gas check bullets sized .357 from whatever mixture I have in the pot lubed with some red stuff requiring about 100 deg. Never pure lead but some WW, some lino, some salvage with tin added. I like the HS 7 @ 10g as recommended by Hodgdon but with F100 std primer, and 15g IMR 4227 also std primer. My loads are not showing any bbl leading at all.

No easy answer and lots of changeable factors, the main reason(s) cast bullet load development is often extensive. The search for the right alloy and right bullet diameter for the load will pay off with freedom from leading and fine accuracy. There aren't really aren't any shortcuts if you do it right, unless you just get lucky and hit upon the perfect bullet for the load from the start.

As for the pressure you mention, I think there often is a greater pressure rise with cast bullets as opposed to jacketed, but staying short of maximum loads, it's probably insignificant.

A number of years ago, I spoke with one of the Lyman guys who was involved with shooting and pressure testing for their load manuals. I wanted to know how much pressure difference there was in increasing bullet diameter by a thousandth, as in going from a .358" bullet to a .359". Granted, a general question, not taking into account changeable factors, and I received an equally general response that the pressure difference was slight. For my purposes, that's fine.

If you have a load that's not leading and accuracy is good, you may have arrived where you want to be or are very close to it.

 

[Tu_S]

Just taking a quick look at what I have on the shelf for projectiles, the unjacketed lead seems to all be longer and would seat deeper, and are a thousandth greater in diameter, both of which would lead to higher pressures for an identical charge.

 

[mikld]

Cast lead bullets have less friction in the bore and require smaller charges. Nearly every bullet manufacturer's manual list their soft swaged lead bullets that also require a much smaller charge/lower velocity to prevent leading.Cast lead bullets are larger n diameter than jacketed so the lead can grip the rifling and seal the gasses in the barrel.

 

[smoothshooter]

Some of the manuals are using swedged bullets rather than cast. Frequently the Lyman Handbooks show higher charges for cast than jacketed as there is less friction moving sown the bbl. Less friction also results in less pressure so the amount of powder is increased, increasing speed and resistance from friction.
Not all manuals due this, some because of their ballasticians, some because of the marketing of cast projectiles they are not selling.

I am not sure about flame temps and leading. I have experimented by putting a dab of grease on bullet bases before loading and firing. The grease is still present on the bullet when it's recovered. If it won't melt grease I have a hard time believing it is melting lead.

I have always used the same powder data whether loading swaged, cast, or jacketed bullets, except when dialing things back to prevent or reduce leading with non.jacketed bullets.
I generally load all handgun ammo to lead bullet velocities.
I no longer load jacketed bullets in handgun ammo anyway.

 

[Hair Trigger]

The main issue with leading at higher loads is the bullet velocity through the barrel. Friction will heat the lead and past a certain point the surface of the bullet begins to melt and deposit along the barrel. Hard cast is not as prone to this than soft lead like factory wadcutters or round nose, because of Tin, Antimony and other alloyed metal with higher melting points than pure lead. A coating will also delay or decrease leading.

 

[Gamecock]

I thought lower loads for lead was due to lead bullet obturation sealing the bore better, making them more efficient.

 

[venomballistics]

I thought lower loads for lead was due to lead bullet obturation sealing the bore better, making them more efficient.

that's more to do with a common progression of problem solving than anything.
Elmer Keith drove cast lead for all it was worth.
Bullet fit was important before coatings went mainstream.
If you didnt know exactly what you had in your hands, fit could be difficult to achieve. and thats where the trouble starts.
You try for a Keith result, you lead line the bore.
You ask for advice you got "Size and lube properly"
You asked how to do that you got "Slug the bore"
You asked why its not working you got "Check the throats"
at this point you might have found the throats to be smaller than the bore making bullet fit irrelevant.
You'd now find yourself at a crossroads of having a gunsmith ream the throats, potentially risking the gun, or living with the issue.
Taking option B... we are on a fast track to 3 grains of bullseye.