I decided that if I wanted to truly HELP, I would just "do the math" and provide the results in a table here. I found a guy on Ebay that is selling lead wire for bullet swaging. The smallest diameter he sells is 0.180" and the largest is 0.475". I'll run a table from 0.180 to 0.500. I can't get all of them "snipped" into one table so there are 10 separate ones. Here ya go:

So, all 'you' have to do is take the number from the column labeled "THE Number" that corresponds to the diameter of your core and divide the weight that you want your core to be by that number. The result will be the length in inches of your core. Personally, since I swage my cores, I would add maybe "a little" (say, 0.05"), to that resulting LENGTH figure (NOT to THE Number), for "sqeeze out". (Note that at a wire diameter of 0.250", THE Number is 140.75 - the same as obtained in the OP.)

Paul

PS - For those that might be interested, I would appreciate it if you would please check this against what you have determined for your actual core length values for a given weight, and report in this thread if the numbers jibe.

PPS - I should note that a difference/error of 0.001" in the TRUE diameter of your core WIRE and what you put in the "equation" for finding THE Number will result in an error of 2.252 units in THE Number.

PPPS - I don't like the name "THE Number". Let's call it the "core length constant" or CLC. At least in this thread. Actually that could "work". As it has been described in this thread, it is unique for pure lead. Were one to use a different metal or alloy, a subscript could be added. For example: Using clip on wheel weights, the abbreviation could be CLCcoww. For lead, CLCpb.

Paul