Purity of lead by weight of your bullet?

It just dawned on me to ask this: I was weighing bullets that I cast the other day and was getting about 175gr for my .490 RB mould. I was segregating by weight and just for kicks weighed a .490 RB from Speer. It weighed 180 gr as I recall. I was always wondering how much pure lead I was getting from my source. Is there a way to calculate what percentage of pure lead is in a bullet based on weight of similar cast bullets? For example both RB's are the same diameter, we could assueme the Speer could be pure lead. How could I use that and the weight to find out how much pure lead is in my cast bullets? Does this make sense?

I don't know that you can find out, short of some very expensive tests. The advice I got when I started asking these kinds of questions was "Don't worry about it, what do you want to do, shoot, or be a scientist?" So.... I stopped worring about it and just cast straight linotype. I shot a cute little 3" group at 300 yards this past weekend from a M94 30-30 with 150's with GC's. Not bad for iron sights(peep) and out of the truck window. Have fun.armjr [This message has been edited by ARMJR (edited February 04, 2001).]

boy, you sure can take the helium out of my ballon in a hurry...

blammer,I'm no physicist, but I think you run into a catch-22 here....In order to determine the percentage of pure lead in your cast R.B., you would have to know exactly which impurities are mixed in there, atomic weights of each, relative amount of each by volume, blah, blah, blah ....... in other words, a chemical analysis. But you can perform a meaningful test, if you are interested.....measuring the actual hardness of your alloy. You would need a Brinnell (sp.?) Hardness Tester, and I THINK you can get something like that from Lyman, SAECO, or Sinclair...somebody has an inexpensive model available. (Sorry I don't have specific info. handy.) You're really into this stuff, eh?!! Good luck.

Yea it's entertaining, people tell me I have a technical mind I don't know.I did not really care about the other added metals etc, I just figured I could find out if my source of lead was ohhh say 85% lead verses 95% lead. Obviously the higher the lead content the better off I am for casting for my Black Powder rifle. I though I could do this based on varying weights of the same volume of space being filled. For example a .490 RB takes up the same volume weather you fill it with pure lead or 50% lead, but it would weigh differently. The closer to pure lead the heavier it would be. I guess I should really ask: How much would a pure lead .490 round ball weigh?

The lead used to make split shot(fishing) is close to pure lead as is that which is used to make air gun pellets. Invest in a box of one of them, cast your .49 ball and weigh. for laymans use the thumbnail will dent and scratch pure lead, so you have your varying degrees thereof.armjr

I'm having a similar difficulty myself. I was given my first muzzle loader by my wife, as an anniversary gift. Took it out to test fire it and stuck the first round ball in the barrel. Then proceeded to break the fiberglass ram rod trying to remove said RB. I pulled the tip off the rod. Now here's where I start to wonder about things being too tight. So I take my dial calipers and start to measure things. I found that I was suppose to be using a .015 patch...it wasn't it was .017. My round ball was suppose to be .490. It wasn't, it was .496. Are these combinations just too much? It was very difficult to load. So in measureing all the round balls in the pack, I found sizes ranging from .487 to .496 If this is common, then the differences in the weight will accompany this.

I'm surprised that no one posted this forumula for you to use to see if you're casting from pure lead.
 
 FIRST: Measure your cast bullets with a good caliper or micrometer. Try not to indent the surface, so that you get as accurate a measurement as possible. The radius is just the diameter divided by 2.
 
 Here's the formula:
 
 4/3 * PI * r(cubed)*.41 * 7000 = bullet weight in grains for a round ball cast of pure lead.
 
 So for a .490 round ball cast of pure lead you will have the following:
 
 4/3 * 3.1416 * (.245*.245*.245) * .41 * 7000 = 176.8gr
 
 (The 4/3 and the PI are usually carried out many places beyond the decimal point--which will make the formula more accurate. I listed it this way for brevity)
 
 So you have a reasonably good source of pure lead if you're getting 175gr for a true .490 round ball. Remember, measure that round ball to make sure of it's diameter and radius! The accuracy of the ball's radius is critical to the accuracy of the formula.
 
 Do not assume that your cast .490, a swaged Speer .490, and a Hornady swaged .490 are all the same diameter! Even a little variance can make a difference.
 
 IF that Speer ball is pure lead and it truly weighs 180gr., something is not right. It is more like .493 diameter, IF it is swaged from pure lead.
 
 You can work the formula "backwards" (if you know you have pure lead) and calculate the diameter from the weight.
 
 So calculate you're target weight for a given diameter;
 then you're going to have to take a sampling and get an average diameter and average weight and plug them into the formula and see whether you're "light". Lighter would mean that the lead has been alloyed or has impurities (or voids). Since no one has access to these new "heavier than lead" alloys for non-toxic shot... you shouldn't have a bullet that is heavier than the calculated weight.
 
 Hope this helps. I got this info. from a good friend who is a chemical engineer, rocket scientist (literally!) and a shooting buddy.
 
 WV_Hillbilly

The theory would seem sound, accepting your friend may have come up with some working substitute variable to account for the average density non-lead alloy mix in the typical lead alloy bullet.
 
 However, that would only work "precisely" if the mixture of non-lead alloys were a constant. Different Bullet manufacturers mix varying amounts of a variety of different alloys to make what they consider the "best" product. Each metal in the alloy has a different density. The exact mixture, therefore the exact average density, of the non-lead materials would be impossible to know without an analysis.
 
 I guess it all depends on how "precise" you need to be.
 
 If you weigh two items of the exact same volume, the heavier one will be more dense, containing most likely more lead.
 
 You could figure a rough ratio of purity that way.

Read the thread "Please check this, somebody" on Hunter's Campfire, above.