Lee 310gr boolits dropping too small?

[ghh3rd]

When I decided that the WW boolits from my Lee 310 gr mold were dropping at 430 early on, I only measured a couple, and was measuring water-quenched boolits that had extra tin. I was measuring them with calipers along the length of the boolit.

I just discovered that many of the air-cooled boolits cast without any extra tin are dropping at 428 - 429. These have aged about 10 days.

I have a couple of questions. Since many factors affect boolit size, at what alloy, 'after cast treatment' (such as water dropping), and aging do you actually decide whether your mold is dropping boolits of the correct size?

What is the correct method to measure boolits -- full length in calipers, or between the bands? I've been getting multiple measurements on the same boolits when measuring between the bands, ranging all of the way from 430 down to 427 (same boolit). Shouldn't it be the same diameter along its length? The boolits appear to be good casts, good fillout.

I suspect that some boolits are a different size from one cavity to another, since I'm getting various measurements from boolit to boolit. I would think this would adversely affect accuracy.

I wonder if I should send the mold to Lee to look at. If I’m wrong, they’ll tell me, and if I’m right, perhaps I can get a better mold. If I do send it, should I send them a few groups of boolits, separated and identified by cavity, or leave it to them to try it out?

Thanks,

Randy

[lwknight]

You have to be very careful with using calipers. Some can be scewed by the amount of pressure on the thumb wheel.
A micrometer is by far more reliable IMHO.

[ghh3rd]

Yes, I observed that when I put extra pressure on the dial, I could get it to read a little smaller, so I was careful not to pressure the caliper against the boolits.

Thanks,

Randy

[dualsport]

IIRC, Lee uses a special alloy to cast their samples with, very high tin content. My guess is they'd say the mold is in spec, but I'm just guessing. I think I remember this mold being offered in two sizes, .429 and .430, unless my mind is slipping(it is). What does your's say on the box? Mine is a .430, with my alloy they come out at .434! And I load them as cast in my SBH, which has cylinder throat problems, but they're plenty accurate, 4"" at 50 yds., probably would go less with a better shooter. Measure your throats, match that. Maybe you'll just have to use expensive alloy for that bullet, but the proof is in the shooting. Try 'em out, you never know 'til you shoot them. Another test for revolvers is to just shove a bullet through a chamber, if it just falls through it's too small, should be a little snug but still able to push it through with a pencil. The Lee bullet was the answer to my problems with my SBH. HTH

[Poodleshooter]

Ok,this may seem silly,but it has happened to me when I dropped air cooled bullets,and was a major reason that I went to water dropping: check the bullet diameter of each bullet lengthwise as you're doing now,but with measurements 90deg apart. See if the measurements differ.
When I was casting too hot, some frosty bullets dropped onto a wet rag to cool would sometimes sag out of round,giving one measurement at .428,and one at .431. My guess was that they became slightly oval from hitting a relatively hard surface before fully hardening. It wasn't really the bands casting at different widths,it was the whole length of the bullet sagging down slightly when resting horizontally as it cooled.
I haven't experienced this since I went to water dropping everything. It might be worth checking out.

[lwknight]

Sounds to me like , you might be just going too fast. If the molds are really really hot and dropping frosty (not just satin) boolits they will be smaller. And evidently oval too.

[sagacious]

...
I just discovered that many of the air-cooled boolits cast without any extra tin are dropping at 428 - 429. These have aged about 10 days.
...

Thanks,

Randy
Tin can be critical to assist in getting proper fill-out, and give you the max as-cast diam in that mold.

Since you already cast .430" bullets, there's nothing wrong with the mold at all and so no reason to send it back.

Aging is almost surely not the determining factor here. The tin content of the alloy almost certainly is. One can "age" a low-alloy lead casting forever without result. Cast with the proper alloy for the mold and you'll get larger castings instantly. Add enough tin until you get proper cavity fill-out. That's the most one can expect from any mold.

Hope this helps, good luck! :drinks:

[ghh3rd]

I'll add some tin, try casting cooler, water drop, and remeasure.

Thanks

[44man]

Good answers. It sounds like the mold and lead temp is swinging too much.