leadmonkey
01-24-2014, 05:51 PM
I've been loading pistol ammo for a while, but I'm new to loading lead, so maybe someone can point out what I'm missing here.
I bought some 40 S&W 180 gr LRN boolits that appear to be very close to RCBS #40-180 online. They are wax lubed, hard cast, and .401 dia. The closest data I could find for a lead boolit of this size at the time was in Lyman's Reloading Handbook, page 364, for a 40 S&W 175 gr lead flat nose (I think) boolit, Lyman #401043. The charge weights for Universal are 4.8 gr start load, 5.5 gr max load. I derated those numbers a bit for the 5 gr weight difference, and loaded some test loads up at 4.8 gr, 4.9 gr, 5.0 gr, 5.1 gr, and 5.2 gr. They leaded up the barrel of my Shield, and even bulged some cases. Way too much velocity I assume, and too much pressure I know.
I have since got a Lyman's Cast Bullet Handbook, and I found data for the RCBS #40-180 in it. (right next to the above mentioned data for the Lyman #401043) The charge weights for Universal are 4.4 gr start load, 4.9 gr max load. Obviously, I had overloaded my first batch of ammo for this boolit. I now loaded some test loads up at 4.4 gr, 4.5 gr, 4.6 gr, 4.7 gr, and 4.8 gr, and the results were much better. No leading, no over pressure indications. Nice shooting ammo.
Why is there such a drastic difference in the charges for two boolits so similar in weight? What is there about that Lyman 401043 that allows such a significantly larger powder charge?
I bought some 40 S&W 180 gr LRN boolits that appear to be very close to RCBS #40-180 online. They are wax lubed, hard cast, and .401 dia. The closest data I could find for a lead boolit of this size at the time was in Lyman's Reloading Handbook, page 364, for a 40 S&W 175 gr lead flat nose (I think) boolit, Lyman #401043. The charge weights for Universal are 4.8 gr start load, 5.5 gr max load. I derated those numbers a bit for the 5 gr weight difference, and loaded some test loads up at 4.8 gr, 4.9 gr, 5.0 gr, 5.1 gr, and 5.2 gr. They leaded up the barrel of my Shield, and even bulged some cases. Way too much velocity I assume, and too much pressure I know.
I have since got a Lyman's Cast Bullet Handbook, and I found data for the RCBS #40-180 in it. (right next to the above mentioned data for the Lyman #401043) The charge weights for Universal are 4.4 gr start load, 4.9 gr max load. Obviously, I had overloaded my first batch of ammo for this boolit. I now loaded some test loads up at 4.4 gr, 4.5 gr, 4.6 gr, 4.7 gr, and 4.8 gr, and the results were much better. No leading, no over pressure indications. Nice shooting ammo.
Why is there such a drastic difference in the charges for two boolits so similar in weight? What is there about that Lyman 401043 that allows such a significantly larger powder charge?