"U" on Lyman molds

[Wayne S]

I've seen a "U" after the mold # as in 311466U, never thought much about it, if the mold cast to a desired Dia. all was well.
Now I'd just like to know what the "U" stood for .

[NHlever]

The "U" on Lyman molds means "undersize". When I started buying molds getting one that was not quite a bit oversize was rare. Folks often ordered the undersize molds to get one closer to their firearm's dimensions. Of course back then we thought that anything more than .001 oversize was a bad thing, and that sizing more than a couple thou was tempting the bad boolit gods. It was also useful if you wanted to use a .31 caliber mold in a .30 caliber gun. I have a couple of 3118, and 311316 molds that are stamped "U", and they are just right for my 30-30's, and .30-06's. They all were molds that were cut from cherries that had been sharpened for the last time.

[BruceB]

The "U" indicates an "Undersize" mould.

At one time it was possible to actually order such moulds direct from Lyman, at least in some bullet designs.

As a general rule, I avoid such moulds. The most-prevalent problem in today's moulds is casting at a too-small diameter. Buying a mould that the maker SPECIFIES to be undersize is buying a problem.

It's easy to size a bullet down a bit. Inflating a bullet to a larger diameter can be rather difficult. If your "U" moulds are working for you, that's very good fortune indeed.

[brstevns]

I have a Lyman 31141 that has the U on it. Drops a perfect .309 with WW. Works out great for my 30-30- and 308 Win.

[Sonnypie]

It's easy to size a bullet down a bit. Inflating a bullet to a larger diameter can be rather difficult. If your "U" moulds are working for you, that's very good fortune indeed.

Aw shucks, Bruce...
Ya just stand them on a steel plate and give em a tap on the nose with yer hammer.... [smilie=1:

JUST KIDDING!
I say, I say, it's a joke son, it's a joke. :roll:

[white eagle]

not to hijack
but there are also #'s other than the mold #
like I have one that is 454424 and lower corner has the 215 on it

[oneokie]

not to hijack
but there are also #'s other than the mold #
like I have one that is 454424 and lower corner has the 215 on it

Are both blocks marked with the # 215?

[scrapcan]

White eagle

The other number is a match number and should be on both blocks to match them as a pair.

brstevens,

your mould is marked 31141U because it is .309. a 31141 without the U would have been .311.

All of this goes out the window with new moulds, it only has some meaning with old moulds.

[white eagle]

Its a older mold and one I will hang on to
beautiful boolits

[dale2242]

Some of the older Lyman molds were made to cast quite a bit oversize.
When I started casting in the early 60s , I ordered undersized molds to keep from deforming the boolits when I sized them.
The U molds cast plenty big to size to proper diameter...dale

[NHlever]

Some of the older Lyman molds were made to cast quite a bit oversize.
When I started casting in the early 60s , I ordered undersized molds to keep from deforming the boolits when I sized them.
The U molds cast plenty big to size to proper diameter...dale


That is normally what I have found too. I have three, or four of the old single cavity "U" molds, and they aren't for sale.

[leadhead]

All lyman molds made today should be marked with U
Denny

[Larry Gibson]

I have two 311466s one is a 311466U. The standard 311466 drops cast bullets of #2 or harder alloy at .311 - .313 depending the alloy. It is a great mould for .31 cal rifles and .30s with worn bores. The 311466U drops the bullets at .310 with alloys of 18 - 20 BHN. It is perfect for .30 cal rifles.

Suggest if that 311466U is, per chance, for sale that you scarf it up ASAP.

I've a lot of Lyman moulds including some newer ones and I find they drop bullets at the correct diameter if a correct alloy is used. Most Lyman moulds are for #2 alloy or linotype and will drop smaller diameter bullets if just WW alloy is used. Temp of the mould, temp of the alloy, tin content of the alloy, size and pressure of alloy fill and the ambiant temp have a lot to do with undersize or correct size cast bullets. I can easily vary the diameter of .30 cal bullets .003" simly by changing from a range lead alloy with minimal tin content to a good alloy of 18 - 22 BHN with appropriate tin content. WW alloy will sit just about 1/2 way between those extremes. unless I add 2% tin to it and then it fills out the mould and is about.002" larger than a range lead cast bullet. It still is not quite the diameter of the 18 22 BHN alloy though.

Larry Gibson