Mold roundness

[Menner]

I have a question my casting and shooting buddy and I got into a discussion the other day and we got micing the nose of boolits that we have cast from different molds that we own and found that there is about .001 to.002 difference in roundness in most of the boolits and these are out of Lee , Rcbs, Lymann, and NOE molds RCBS and NOE seem to be the closest to being truly round. using COWW and all the boolits are at least a week old not fresh out of the mold.
Now the questions
is this much out of round common?

in your much more informed opinion will it cause accuracy to suffer? ( at longer ranges 200yrds and out)
or is it a nonissue and I should just stop over thinking and shoot

and what about lapping out just the nose area of the mold with valve compound?

I eagerly await answers from on high

[Buckshot]

...........We don't like to see it, but it is usually there (runnout) in some form or another. Speaking of production moulds made for the public, ie: whoever has the $ to buy one, then some amount of run out will be there. I have tried to be realistic about it and to consider it's implications with what I'm trying to accomplish. You should keep an open mind about it. I'm not suggesting you should forgive obvious sloppiness, but you should also NOT expect perfection from a production mould.

One of the finest moulds I have is a years old SC Lee C309-160-RF that is perfect. It's impossible to detect any offset across the parting line. It established my feeling that lathe bored moulds were the best. And I subscribe to that to this day. Yet for the money we pay we expect other mould blocks to live up to it. I have at this moment have a Saeco 2 cav set of blocks I'm going to send back to them. They drop slugs with a pronounced seam at the parting line, and they are offset by a good .002" across the parting line. For what I paid for them I'm very disappointed in their performance.

I dislike that I have to send them back but I do not bear them any ill will as I have several other Saeco's that are near perfection. In the world of machining metal a certain number of them will be at, or near perfection and the balance will not be. Consider the firearm you'll be using them in, and how you will be using them.

...........Buckshot

[GP100man]

Good answer Buckshot, I feel if accuracy is acceptable & lookin at the boolit in a 3 diminisonal way & it`s not out of balance trying to lapp 1-2 thousands would do more harm than good, especially on softer molds such as aluminum or brass & even on true 90 degree edges on steel molds .

A few yrs. back I bought a ole IDEAL SC 429421 from Erik as is , he did clean up the face of the mold & I put on a new thicker sprue plate . Anyways I degreased it & cast a batch, needles to say the blocks would wiggle just a bit, just a tiny bit mind ya , anyways sizing proved to take care of the drivin bands (even the front one mind ya , but the oglive was off setby .0015" the best I could measure.

I thought ugh oh ! , but for the price I could`nt complain then & not now !, BUT, I put my usuall plinking powder under it & as I stepped out of the loading room I heard crows in the feild , & there `bout 80yds. was a bigun` I leveled off (like I really intended to hit em)I did`nt hit em (expected results) but hit close enuff to em the dirt spray knocked em over & sorta disoreinted em a second!

The point is sometimes we get surprises when we least expect em , even when we know it should`nt be!

GP

['74 sharps]

Your bullets should shoot fine.

[bhn22]

Do remember that upon firing, they will be as perfectly round as the barrel is. The real trick on our part is to make them seat as square as possible to the bore, which is why we normally size to fit the throats. If you can do this, the .002 you see will be pretty insignificant. Bullet fit is king.

[Menner]

Yeah over thinking it. see what happens when the weather is to bad to shoot and you have a mic and a bunch of boolits laying around and nothing better to do than invent problems for your self