Does tumbling the lead balls cause surface hardening?

[Bo T]

Thank you. It seems that a person, if they know, the % alloying element should be able to predict the hardness or vice versa?

 

[Bo T]

My goal is to tumble the cast balls. Life is complex enough without having to worry about sprue alignment.

 

[mooman76]

You don't really have to worry about sprue alignment all that much. It is best optimally but there are allot of things to improve your accuracy like weighing the PRBs and such but the average shooter won't be able to tell the difference unless you are a bench shooter. The Lee mould leave the PRBs pretty much Sprueless. But if you want to tumble, go for it. Nothing wrong with that.

 

[M. De Land]

Bill, I do a lot of casting with mostly pure lead for balls, which by the way actually has a BHN of about 4.7 not the 5 that is usually quoted,along with lead/tin and lead/tin/antimony alloys for rifle and pistol bullets.
I have and use two lead hardness testers, one from LBT and one from Lee to accurately compare hardness yields.
Pure lead is not effected by water quench or impact hardening that I can measure.
Lead/tin and lead/tin/antimony alloys will age harden for about two weeks after casting and then the lead/tin mix will spontaneously soften a few points after a year.
I'm told but have not tested that lead/tin alloys can be kept frozen to slow the age soften process that happens at about a year after casting.
Water dropping lead/tin mixes does not seem to have much effect if any. Also Tin alone will only harden a bullet to about 9-10 BHN then your just wasting tin as it will not go any higher without antimony which establishes a micro-crystalline structure known as "trees" that serve to harden and strengthen the alloy.
Lead/tin/antimony alloys will greatly harden to a water drop ( up to a BHN of about 40) is possible with oven heat treat and water quench.
Antimony alloys of about wheel weight consistency will water drop to a BHN of 12-14 and hold their hardness for many years.
I have some pistol bullets in cans I cast over 15 years ago that are still within a point or two of original BHN measurements.

 

[Golfswithwolves]

My goal is to tumble the cast balls. Life is complex enough without having to worry about sprue alignment.

A very wise member of this forum (sorry but I don't recall who for sure) once pointed out that if there is no sprue remaining on the ball, then you just don't know which end of the ball is the front. :bow:

 

[M. De Land]

That was not my saying but it certainly agrees with my view.
I know that any casting void will almost certainly be under the sprue and if I can't find the sprue a void could be orientated any where when seating the ball.
One could avoid this worry by weighing them all I suppose.

 

[FishDFly]

Doesn't change it chemically, but lead balls heated in an oven at about 400 degrees for half an hour and carefully poured into cold water will created a hardened surface...the centers will still be soft. Have played with it but rally found no great use for the end product outside of possible deeper penetration. Alloy mixed balls will soften slightly if heated the same way then allowed to cool by turning off heat and letting them cool with oven door cracked open.



Please share your testing methods and results and how penetration testing was done.

 

[Billnpatti]

I know a shooter who tumbles the lead balls after he's done casting. He claims that it removes the sprue and makes the balls rounder. I don't know it it's true but he is awfully hard to beat.

I do that to all of the balls that I cast and have found it to be quite true. :hatsoff:

 

[Billnpatti]

"Lead/tin and lead/tin/antimony alloys will age harden for about two weeks after casting and then the lead/tin mix will spontaneously soften a few points after a year."

Now, that is interesting. I surely did not know that. All good info. You seem to really "know your oats". Thanks for sharing. :hatsoff:

"I have and use two lead hardness testers, one from LBT and one from Lee to accurately compare hardness yields."

I don't have a lead tester but I had a method that I read about that involved using one piece of pure lead and a piece of lead of unknown hardness. You placed a steel ball between the two pieces and placed them in a vise. You tighten the vise until the two pieces are almost touching and then you measure the diameter of the dents in the two pieces. Then with a little mathematical massaging of the data, you came up with the hardness of the unknown lead. It came from a reliable source and I wanted to keep it for future use. I wrote it all down and put it away in a safe place. Too damn safe as it turns out because I can't find it now.

 

[M. De Land]

I am familiar with the technique Bill and have the article if you want me to post technical info.
It's in the NRA publication by Johnson I believe on all aspects of lead bullet shooting and casting.
There is not much in it about round balls and pure lead if memory serves correctly.
The other thing is the lead on one side of your vice jaws has to be certified pure or your control is skewed.

 

[Bo T]

Couldn't you determine if there is a void just by spinning the ball? Odds are that you won't set the void perfect top or bottom center.

 

[M. De Land]

I think weighing it would be faster.

 

[nhmoose]

PB will not harden with water drop however alloyed with tin and antimony yes it will quench harden very well. Trick used with Wheel weights for decades in pistol and rifle bullets.

Pure nope not measurable to me with my hardness tester.

 

[Bo T]

I hadn't considered a simple balance arm, with a solid ball as the counter weight. I've been using the electronic balances for so long.