Coated bullets solve many issues with cast bullets. I've been coating for 3 years and have done from bunny farts to full power loads without any leading in 9mm, 10mm and 45. Ive also coated and cast bullets for a friend in those calibers plus .357. no issues with leadand to date would number around 20,000 of my own coated bullets and many more that were Hi-Tek and that's why I suggest them.
Non coated cast bullets require a little more work sometimes to prevent hours of barrel scrubbing and soaking to remove lead. In most cases leading doesn't become an issue and a lot depends on whether it does or not. A 9mm pistol with a bore size of .355" shooting a load within published data from most any cast bullet company will most likely not lead that barrel.
Bullet hardness, obturation, and bore size span more than one gun type and different measures to prevent leading depends on that type and each gun Including chamber pressure and velocity. That's the reason why people have different experiences with what it takes in what gun and what accounts for leading and what doesn't. A forcing cone sizing bullets down too much can and has caused leading for by swaging the bullet down in some cases and gas cutting (even with harder bullets) can occur if it doesn't fill the bore well.
Different experiences often yield different results and add to the confusion of what cast bullet hardness should be. Not to mention reduced loads and the lube used. BHN, pressure and velocity as it pertains to leading was worked out in testing years ago. Factors in the gun and differing load often lead back to confusion as to what is good and what isn't rather than what caused it.
One perfect example of those changes is a larger bullet and barrel fit. It often fixes a leading issue that still may have been fixed with a softer bullet. Making a bullet big enough in a semi-auto pistol so that the bullet is swaged by the bore (slightly) often has the same effect as obtruation and eliminates the need for it. Yet that same bullet may raise pressures in another semiauto with a smaller bore size and cause more problems. That is an issue for someone with different guns and bore sizes and two different size bullets are needed unless the BHN and pressure of the load are used to eliminate that need by good obtruation.
From one of my favorite resources for compact and detailed cast bullet information.
Note: Lyman #2 has a BHN of 15
Approximate "Maximum" Chamber Pressure For Lead Alloys (PSI)
Plumbers lead, stick on WW 13,000 - (Black Powder Only)
Wheel weights / clip-on
25,000 - Non-Magnum handgun
loads, Rifles to 1,900 fps
Lyman # 2 (alloy varies in
Lyman cast bullet books)
35,000 - Magnum handgun &
rifles to 2,000 fps
Quench-cast WW (dropped
from mould into cool water)
48,000 - Magnum handgun
& rifles to 2,200 fps
Oven heat treated WW
55,000 - Jacketed velocities in handguns
and rifles with quality bore & balanced load
"A very common misconception is that leading is caused by the bullet being too soft. Historically, tin was used to harden bullet alloys. Today tin is used to lower the surface tension of the molten alloy and allows it to fill out the mould more completely. Antimony hardens lead alloys much more effectively than does tin, in addition, antimony allows the alloy to be hardened via heat treatment, something the chemistry of tin doesn't allow (and arsenic is even better for heat treating than is antimony)."
"The formula (from the pages of HandLoader Magazine) to determine at what pressure an alloy of given BHN will obturate the base of the bullet and seal the bore. If the bullet is too hard to obturate, gas cutting usually occurs on the base band on the non-driving side of the rifling and barrel leading is likely. Simply multiply the alloy BHN by 1,422.
Example: Alloy BHN of 12 multiplied by 1422 = 17,064. An alloy of 12 BHN should be used with a load that develops a "minimum" of 17,000 psi. Need more info on minimum / maximum alloy BHN? These Glen E. Fryxell articles explain alloy BHN in easy to understand language."
From LASC Website found here : http://www.lasc.us/CastBulletNotes.htm
More on leading : http://www.lasc.us/Fryxell_Book_Chapter_7_Leading.htm
MAin page:
http://www.lasc.us/
A resourceful forum for everything about casting, loading, coatings, paper patching, and more at: http://www.castboolits.gunloads.com/
