was just a general question. Only kill paper targets, so i shoot mostly lead. load 100 grain 380,158 grain 38 spec 357,124 grain 9 mm, 175 grain 40 s&w and 10 MM.
357reloading, the primary difference in load data between lead and jacketed bullets has to do with the bullet diameter and the material the bullets are made of which translates to bullet-to-barrel fit that directly affects chamber pressure. And yes, jacketed bullets generate more friction with the rifling than softer lead lead bullets (although most lead bullets are harder lead alloy).
Jacketed bullets are smaller in diameter than lead bullets of the same caliber (typically 0.001" smaller):
9mm: 0.355" jacketed vs 0.356" lead
45 ACP: 0.451" jacketed vs 0.452" lead
Most factory barrels are cut to match the smaller diameter jacketed bullets and when fired, there are gaps that exist between the bullet and rifling land/grooves where hot gases escape around the bullet which decreases some chamber pressure. With the larger diameter lead bullets (typically 0.001" over the barrel diameter), the softer lead alloy "digs" into the rifling when fired to seal the bullet against the bore of the barrel and you have less hot gas escaping which increases the chamber pressure. This is the reason why lead load data is often lower than jacketed load data.
As to leading, when a lead round is fired, you will have hot gasses escaping around the base of the bullet and the heat from the gases will soften the base of the bullet causing leading near the chamber end of the barrel bore. So check the barrel bore size or slug the barrel to determine the barrel size and order the lead bullet that is 0.001" over. Gas check prevents the base of the bullet from melting from this heat and reduce leading (think of it as jacketed bullet wanna be lead bullet).
However, even shooting properly sized bullet (0.001" over) will cause leading in the barrel if pushed too slow. Why? When the primer ignites the powder, the expanding gas pushes hard on the base of the lead bullet like a hammer. This pressure shot wave expands the base of the lead bullet a bit and help seal the bullet to the barrel - this is called obturation. If you shoot light "paper punching" target loads, the base of the bullet may not obturate and still allow some hot gases to escape around the base of the bullet, and this causes melting of the bullet base and leading - also called "gas cutting".
So, you have two options if you want to minimize leading:
1) Increase the powder charge until you get proper obturation of the bullet base without exceeding the max load.
2) Shoot softer lead bullets that will obturate with lower powder charge. Most commercial lead bullets are available at 12-24 BHN range. If you push your bullets to max load data, 24 BHN will do well. 18 BHN will do well at mid-high range load data and 12 BHN will do well at low-mid-high range load data. If you are looking for lighter target loads,
Missouri Bullets carries lead bullets at 12 and 18 BHN.