I did a check on some of my cast bullets and here are the results - I am somewhat disappointed! 

Here are the results where I faced them down in my lathe - maybe a 50 mil cut each time:

Recent cast session ~ 25 bullet lot: tested the heaviest @ 427.9 gr, and the lightest at 427.4 gr - Result: No voids!

Earlier cast session ~25 bullet lot: tested the heaviest at 427.1 gr, and the lightest at 426.8 gr - Result: No voids!

Earlier cast sessions: 425.8 gr and a 424.4 gr - Result: No voids!

At this point I thought maybe my lathe tool might be closing up voids as I was facing off the base of the bullets so I tried a 15 deg. radiused profile insert - 424.5 gr - Result: No voids!

This is maybe good news if I'm not doing anything wrong with the lathe operation.

My bullet mold is a Paul Jones. I have been trying different melt temps from 780 to 825 deg. I use an RCBS 20 lb melt pot and it is controlled by a PID. Alloy is 15-1. I faced off most of all the shanks of the bullets.

I've made several gang fixtures(different moulds) that get used to mill bases. They do 11 at a time. 

First one was for a rather oddball factory Savage 7-08 barrel.... they made it for a year or so with an 11 twist,total flop. So I started this notion because of wanting to shorten an existing bullet to see if it worked. It did,and did so especially well... forget the details which were written down. Have other 7-08 cast rigs with more conventional twist.

Using Lee moulds is an adventure..... to say the least. 

A cpl years later.....
Next bullet was a Lee 309-150rf for an especially accurate R700V. I make tapered nose sizing dies along with my own H&I so none of this is that big of deal. Keeps my pea brain engaged. This particular Lee mould though really works well in the 308 V. So made another gang fixture for milling bases.

Our Bridgeport has more important $$ things to do than milling cast bullet bases so I found an absolutely mint the little Atlas bench drill press. We have a bunch of beautiful Walker Turner DP's in our shop.... the little Atlas is for the loading room. Snagged a XY table off Ebay for it along with a low profile vise.

Used an absolutely piece of garbage new 3/4" router bit,mainly to get it out of our cabinet shop(came in a tooling lot). Just sayin,this is a really junky bit. The results have been great. My best casts can see very consistent weights but Lee moulds have cheapy sprue plates so there was some left on the table WRT getting spot on. The .5 'ish weight range all but disappeared. But more importantly the bases are deadnuts 90* to the bullets long axis. 

I enjoy making loading tooling meaning,it isn't a chore. The time it takes to mill 11 bases on the little Atlas is hardly worth mentioning.... it's quick. 

Sorry for the novel.

Lee moulds and their cheap sprue plates. As per my post above,the original idea was for shortening an existing design..... the results ended up showing how certain aspects,in this case Lee sprue plates.... can have an effect. Not the least of which is any base/axis squareness.

About a year? ago.....

Looked at Charpy impact tester design and chose to come up with an instrument that more represents the challenges of cast at launch. So a vertical impact tester was built. Now back to square bases....

One observation of the milled bases is how they handle impact. Reluctant to say "better" for fear of sounding like I'm trying to "sell" the idea.... am not. Just sayin... milling bases deadnuts perfect does help in some aspects. 

Have made sprue plates from scratch... so am no stranger to nice plates. I'm a guest on this forum... my interest is cast bullets. Don't want or "need" to take discussion into the weeds. Only posted because I thought it might help you in some way?

As hepburnman found out via his lathe testing, you will not find visible voids inside even poorly cast bullets.  Variations in weight of perfectly good looking bullets are caused by casting porosity or shrinkage voids which are usually too small to see and generally cannot be completely eliminated, only minimized.  Here's a link to an article I wrote some time ago on the variations in weight of cast bullets which you may find interesting.

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Wayne

John in PA wrote on Feb 23^rd, 2024 at 1:36pm:


I assume you read this article ( (You need to Login or Register to view media files and links)), which was referenced in the earlier article link I posted.

There's a fellow (HATCH) on the Cast Boolits forum that sells PIDs ( (You need to Login or Register to view media files and links); Or you can make your own.  Instructions can also be found on the Cast Boolits forum.

Wayne

John in PA wrote on Feb 23^rd, 2024 at 1:36pm:

I have two casting furnaces (an early RCBS pro-melt and an Lyman) and I use just one PID controller. I don't remember off hand who I bought mine from but I purchased two thermocouples as well, one for each furnace. These stay in-place and I just move the PID controller from one furnace to the next (I don't cast with more than one furnace at a time  ).

The idea that lead settles out of a lead tin alloy is complete fantasy.

Jeff_Schultz wrote on Feb 24^th, 2024 at 7:11pm:


Agree one hundred percent and it was backed up by a friend of mine with two doctorate degrees in engineering that worked at a nuclear power plant.
Some people just do things because it makes them feel better.