Boolits Fracture During Heat Treat?

[rhubarb]

This is my first attempt at heat treating boolits. These are Lyman 225415 55gr.

I had already checked and lubed them when I decided to try heat treating. They all cracked right where the gas check crimps into the base. I've since heat treated some before applying checks without this problem.

Checks are Hornady. Sizing was done with Lee .225 push-through die.

Heat treat was done in a yard sale toaster oven set on 450 for one hour before dropping in ice water. There were initially a few small cracks when I removed them from the quench water. The cracks opened up more over a few days.

This is not good, right? Might these not shoot real good?

http://castboolits.gunloads.com/attachment.php?attachmentid=15916&stc=1&d=1253319743

[felix]

Happens when the boolits' antimony/tin ratio is not correct and the boolits cool TOO fast. I have seen it with 22's only so far in 40 years. Do not shoot any of them. Remelt and add some tin, and retry. ... felix

[Shiloh]

I have never heard of this!!

Do larger caliber boolits cool a bit slower allowing the structural lattice to stabilize??
Sounds like great advice from Felix.

Shiloh

[qajaq59]

I had already checked and lubed them when I decided to try heat treating. They all cracked right where the gas check crimps into the base. I've since heat treated some before applying checks without this problem. I'd never heard of it either, but I'd say Felix has the answer.

[Pat I.]

I've had wierd things happen even with 30 cal. bullets if I HTed with the checks installed. I run the as cast bullet through a Lee push through die before HTing and then lube and put the check on in a lube sizer using an H&I die .001 larger after HT. Works for me.

I don't think you need to use ice water either. Tap water will give me a BNH in the 30s using WW with a little chilled shot added 24 hours after quench with the toaster oven set to 440 degrees.

[Matt_G]

I'm wondering if it was the ice water that caused this.
I have heat treated many gas checked boolits (not lubed) and have never had cracks appear, but I've always used water straight from the tap, no ice.

[Ron.D]

I've never had it happen and in the winter I use winshield washer antifreeze. I leave it outside @ -20 then bring it in and quench. No problem. Mostly .358's Ron.D

[felix]

358's have plenty of latent heat, Ron. The 22's just don't have enough, i.e., too much surface area. Colder water works mo'betta' in proportion to the latent heat within a boolit. Room temp water is plenty cold for the smaller boolits. The idea is to leave the boolits in the pail as long as it takes to get the boolit centerline just as cold as the outside circumference. In never hurts to leave them in the pail overnight. The next morning you can put them into the oven at 200 degrees for several hours to radically speed up the hardening. ... felix

[felix]

Matt, ice water had nothing to do with it. The damage gets done via the rate of cooling down from HOT through 200 degrees, say boiling water. ... felix

[243winxb]

What alloy are you using?
I've since heat treated some before applying checks without this problem. So you fixed the problem. Great. To heat treat, the bullet diameter as it drops from the mould must be the correct diameter you need. You can not heat treat a lubed bullet w/ GC on it. Any temperature tap water is fine. Adding tin is not a good idea for water dropping. 2% or more of antimony is needed. Air cooled with the Lyman #2 alloy works very well, or 6% antimony, with 2% tin. Remelt the cracked bullets.

[Ole]

I've had this happen water dropping .460 ranch dogs if the mold gets too hot.

The problem goes away (at least for me) if you let the mold cool down a little and slow your casting tempo.

[felix]

True, boolits too hot tend to get consistent and uniform air holes throughout the boolit, rather than more random and large. Just don't let these extra hot boolits cool too fast. Keep them in the mold until the sprues harden a little more than the optimum for speed production. That should help the high antimony boolits stabilize. ... felix