First off you might want to do a little testing prior to doing a lot of blending and smelting.
Testing with some muriatic acid first will go a long way in finding out if you have any zinc mixed in or not. It only takes a drop on an ingot to determine this. IF it foams or fizzes you have zinc, if not your clear to mix and blend as you want. It doesn't have to be full strength industrial type either some drain cleaners have plenty in them to indicate zinc presence or not.
Get a lead thermometer for sure and use it when your smelting. Go slow and bring the heat up as necessary to get things melting. Most alloy should melt at or below 700 degrees, and should be good and liquid by then as well. IF you find your pot full is chunky like oatmeal at 700, set that aside, and use something else for the time being. Also while smelting go ahead and use some sawdust to flux it out really well. This will give you real clean ingots that can go straight into your pouring pot once you done.
Those couple of little things can become big things once you get fired up and start blending alloy. The chunky part can sometimes be an antimony rich alloy which might be really hard until you blend it down with some soft stuff, but it can also be an indication of zinc. Thats why I suggested you test with the acid first to eliminate that as much as possible form any mystery metal.
I started off much like you, I had an accumulation of what I knew it was or and what it might be to start out with. I read a ton over on CB's and asked many questions via post and PM's. At the time my main concern was pouring up bullets for my 454 which is a powerhouse when it comes to cast, and having experienced a major leading issue years previous I had no desire to repeat that episode.
I had a small amount of wheel weights that I had smelted down into ingots. So i at least had a base from which to work. I really didn't want to spend a small fortune on tooling until I was sure I could make this all work out. So I was directed over to the following link,
Testing Hardness with Pencils
This might sound a bit iffy, but trust me, if you follow the directions you will be within a point or two either side of what most testers will read. This was what I started out with and used to work with my unknown alloy. I have since purchased a
Cabine Tree Tester and found this to be true, at least with the different know alloy I have on hand. What I like about this particular tester is that it can be used on bullets or ingots of varied sizes and still get repeatable readings. For testing ingots I like to use one of the small cube shaped molds like a Lyman, Castboolit, or RCBS, that throws one out around 2" x 1"x 1" square shaped. These give the best readings IMO. I also will sometimes pour out a dozen or so bullets of a RFN design and use them as well.
One thing you need to remember is that ingots will cool at different rates than bullets will. This said a big thick ingot might be actually harder or even softer than what a bullet cast from it is, simply due to the differences of cooling. Smaller amounts will cool quicker and due to their properties might be harder. Still if you have 38 ingots all within the same area, it stands to reason your bullets will also be somewhere within the same spread once poured. Your simply looking for a place to begin, and to adjust to from there.
That said I took some of the ingots I knew all came from the same place and blended them into one big pot full of alloy. I then poured this into small ingots of all the same size, which were cooled at about the same rate. I waited two weeks before testing to alloy the properties to all stabilize somewhat. It sounds like a real pain, but you will find it isn't much once you get started. After the two week period I tested with my pencils and wrote the results on the ingots with a Sharpie marker. In the mean time I had also smelted up my unknown alloy and poured it into smaller ingots as well. What I ended up with was some soft stuff that was around a 9'ish BHN and some that came out at around a 15'ish BHN according to what the pencil tests suggested. I then took 4 ingots of each and blended them together for a small batch of around 5#. Again I waited and after 2 weeks I tested these. The resulting alloy came in at around a 12-13 BHN which was right where my standard wheel weights were hitting. At this point I simply set up equal weight piles using ingots form each stack and then smelted the whole mess into one alloy.
So yes this can be done, but like mentioned you need a starting point and a goal your looking to end up with. Before I would tell you to simply blend it all up into one mess, I would first recommend you make it all into a couple of piles of individual ingots first and alloy them to cool at a close rate. Then simply random test a few from each stack and see where they land. This will give you a much better handle on what your working with, if that matters.
I hunt with the bullets I am pouring so I want each batch to be as close to the last as I can get. I keep my ingots separated in plastic tubs so I know exactly what is in each. I keep my mystery metal in as received condition so I know it's properties aren't known. This is the stuff I pour up practice ammo for shooting at the public range. Everything else is shot on my range and is recovered, bagged, and tagged, so I can resmelt it later on.
Read through the link(s) above, and it will give you a good start to at least finding out what you have on hand. Find you a good ingot mold and something to smelt up 40 -50 pounds of alloy in. If you have something you somewhat know the content of, pour it up first and use it as a base line for your other testing. Just remember though that even range lead poured up and cooled at different rates can and does show different hardness between ingots. That is why I mention to separate what you know from what your guessing at. It might be the same, but some might have zinc or other stuff in it as well.
Hope this didn't bore you to tears, and helps out some. Getting started off can be somewhat daunting for sure, but once you get a handle on a few basic things you will be miles ahead, and pouring up bullets of good quality and repeatable performance.
Consider this: Elmer Keith designed and popularized the .44 Magnum using bullets with a 16-1 alloy. The hardness of these bullets that reached velocities in excess of 1400fps? BHN of 11. So, no, I don't buy the 1440 x bhn formula at all. I load .357 Magnum and heavy .45 Colt loads regularly, and my bullets never exceed a BHN of 11. A correct bullet diameter and a good lube goes a long ways in lead bullet loads. Regarding your 148gr wadcutter loads, if you can get some pure lead such as sewage pipe at your local junkyard, just add some harder alloy to that along with a little solder and you will be fine. Just MHO.
