Why are lead handgun loads lighter

O

osborne

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Just wondering, why are lead hard cast loads lighter than those for jacketed bullets. I just recently started loading lead hard cast and I'm wondering why????? I realize lead cannot be driven to rifle velocities but take for instance .40 S&W, it's what I'm loading. A 180 gr. jacketed bullet load starts at 5.8 grs' of unique while the max load for a lead bullet is 5.5 grs. of unique. Both loads seem subsonic, even a max load with a jacketed bullet is just borderline to supersonic. So what gives???

Pressure for max loads with both bullets are very close but I would have thought that lead would offer less frictional resistance as compared to a jacketed bullet. What am I missing?

Osborne
 
One possible reason is that unless they have a gas check, the rear end will start to melt as they go down the barrel. Hence the conidtion of leading up the barrel.

I'm sure there are other reasons though.
 
All things being equal a lead bullet will give higher velocity for the same powder-charge. Jacketed bullets create more friction in the bore.

44Bore
 
There are a couple of factors at work here, maliability and friction;
1) lead is soft the pressure of the burning powder will cause the lead to spread out into the grooves and work as a better seal
2) the other reason is that lead is a lubricant and will gladly slide along your barrel.. I hot loads it does melt but that's not really a good thing.. if you can avoid it don't melt your bullets in the barrel that ain't good for you or the gun that is what causes leading ....

End result less powder will give you the same results....
 
Leads expands under pressure and seals the bore better than a jacketed bullet. Called Obituration. Bullet actually gets shorter and larger in diameter. Requires less powder to produce the same pressure and velocity. This will be affected by the hardness of the lead, type of lube, shape of bullet ....etc.
 
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