Water Quenced - Smaller than Air cooled?

[dmftoy1]

I need to cast up some bullets for my Mosin tomorrow. I thought I had some from my last Enfield session that I could use. They were 314299's that had been water dropped. When I put the Mic on them they came out at .3105 . .is this due to my poor technique/alloy or the fact that I water dropped them? I guess what I'm asking is whether water dropped bullets come out a bit smaller than you're expect or ? The bullets looked to have really good fillout so I'm a little bit surprised that they were as small as they are.

Any advice is greatly appreciated.

Have a good one,
Dave

[Ricochet]

You're measuring them when they're freshly dropped. Much of the antimony is still in solid solution. As it crystallizes out the volume will increase. Air cooled boolits do this while they're slowly cooling.

[dmftoy1]

Nope, these are being measured about 2 months after casting them. So I shouldn't expect any size difference in water quenched vs air cooled?

Regards,
Dave

[MGySgt]

If you have any from the SAME alloy that were AC veruses WD - measure them and see.

If you don't have any - run a short test. Mould some out of the same pot and do WC and AC and then wait a few days and see if there is any difference on the average.

Interested in what you find out. I think I may run the same test with a 31141.

Drew

[dmftoy1]

Alright, I'll do that. I wonder if I was just running the pot too cold or something. I typically try to stay at 700-750 and now I'm wondering if I should be up near 800. I'll do some WC and AC out of today's batch and then measure them to see. (same pot of metal)


I thought someone would come on and quote some physics and metalurology that I didn't understand and give me an answer! :)

[Bass Ackward]

Temperature does different things to different molds depending on the stresses in the metal.

Some blocks expand inward on the cavities when you heat them over a certain point and the metal expands. Some blocks expand uniformly outward and the cavities just get larger molding larger bullets. Sometimes the blocks do different things in different place.

I have one mold that if you try and mold frosty, the nose shrinks and the base expands thus giving you a tapered bullet. The nose drops to .431 and the base expands to almost .435. I have other molds that do the exact opposite at the same settings with the same mix.

Mix will dictate what happens when you change heat. Sometimes over heat will actually shrink a mix or shrink it in places. Sometimes molding to fast will do the same thing at the exact same heat setting. Smoking your mold will reduce diameter and visa verse as it wears out over a session.

Bottom line is that there are no hard fast rules. And because of that, these are the things that you should record on paper for each specific mold. It is too much and too hard to remember everything about every mold that you will acquire over time. Instead of learning the lesson over and over again and wasting time, you can simply dial up what you need, to be where you need to be.

Then you will come away smiling that the end product will work.

[dubber123]

The only time I actually noticed a difference to any great degree, was a while back when I decided to water drop a batch of .45's. I had honed my sizer out to not touch the boolits and give me the fattest slug possible, as the mould always struggled to make .452". I lubed the water dropped boolits, but when I loaded them, I for some reason had to back off my taper crimp die. Thinking little of it, off I went to a pistol competition, where I soon found NONE would chamber in my revolver. I later found this entire batch, (20 lbs.), had grown to .453+, way fatter. I didn't have a die that small, so I cast another batch and air cooled them. Bingo, right back to .452". I'm sure Bass is right, too many variables, but I know it CAN happen.

[dmftoy1]

Well I cast up about 400 today and randomly alternated between air cooled and water dropped. The alloy was hotter than I had been running it (790 degrees) and I cleaned the bejesus out of the mold before smoking it, preheating it and then starting casting. If anything it seemed like the water quenced might be .0005 smaller. On some of the one's that were measuring smaller though I noticed that the fillout wasn't quite as sharp so it could've just been poor technique or ??

The good news is that I got a whole bunch of them to drop at .313 and .314 so I'm pretty happy. I'd liked to have them all drop at .314 but given that my sizing die is a .312 I guess I'm good to go. (the last batch were all at .310 and .3105

Have a good one,
Dave