Lee mold accuracy..??

[Don Steele]

I recently acquired a new Lee RB mold. It is labeled.395.
I cast a mess of balls with no issues. When I took the cooled balls to my scale for weight grading, I found them coming in at 90.5 gns in a very tight range(good precision), but not the 92gns I was expecting. Measuring the balls with a decent caliper showed them to be .392 in . Not the .395 I was expecting.
When I ran .392 in. Through the equation to predict the weight, sure enough... 90.5 gns would be the expected wt in pure lead, so I'm satisfied my metal is good.
So, my question is whether anyone else has found this anomaly with Lee products.
Thanks,
Don

 

[Richard Brinkman]

Yep along with newer Lyman, Saeco, and RCBS the all cast undersize any more. The best of the lot is the older Lyman most of them cast the correct diameter for me anyway. Your mileage my vary.

RB

 

[George]

I've never had any such problems with my Lee molds. I have an older one, 30 years, at least, in .395. I recently cast 104 balls with it, they measure .395 and the weight range was 91.5-92.4. I bought a .380 mold last year, cast 250 balls which measure .380 and the average weight was 81.9, calculated weight 82.4.

Spence

 

[ZUG]

Yes -- I also find this happening with my Lee molds - round ball or modern bullet style with pure lead or wheel weight lead. Mass production and lack of quality control I guess? Also the price for labor might figure into it - less time in the factory - more profit :hmm: .

 

[nkbj]

My Lee .395 casts .397's.
I got extra for free! :haha:

 

[Maven]

It's a rare thing to find a mold produced by any manufacturer, including Jeff Tanner, that casts to the advertised (exact) dimension using pure Pb. Some of mine come close, but not exactly as specified. Unless a mold is grossly undersized, you can make up the difference by using a thicker patch and/or a harder alloy. If grossly oversized and new, see if the manufacturer will replace it. Btw, I have a dual cavity Lachmiller (now RCBS) .451" RB mold in perfect condition, which casts beautiful, but way undersized RB's. Anyone need a .447" RB mold?

 

[Len Graves]

Has anyone contacted the Lee mold co. About this? I use Lee molds and haven't had any discrepancies. Do you think they might want to know? Perhaps someone here has contacted them on this problem. If so what was their reply?

 

[Don Steele]

I'm Currently awaiting a reply from Lee.
Posted here to see if others have made similar observations.

 

[longcruise]

My .535 throws them at .533. Shoot just fine so it's ok by me.

 

[robert reed]

My .490 throws .492. Hope to break in a new .575 this weekend. Curious! :hmm:

 

[mooman76]

Most of my Lee moulds in RBs throw a little big but most of my lead, even the soft stuff has a little bit of tin which will make them throw larger, slightly.

 

[curator]

Pure lead will often not fill the mould completely unless very hot. You might find that using a good lead thermometer and getting your melt to about 750-775 degrees will allow your mould to cast at the desired diameter. A tiny amount of tin will allow a slightly lower temperature as it acts as a "wetting agent" when added to pure lead. Even as little as 0.25% will help with mould fill-out but not cause appreciable hardening. Generally, Lee moulds are right on for diameter.

 

[Don Steele]

To their credit, I received a reply from Lee Precision the same day I emailed them about my concern. I'm very pleased with the speed of their response and want all to be aware of that.
Here is what they sent me:

"Please return mold, with sample balls and if it is not stated diameter, minus .002, we will replace it for you."

Given that they apparently only warranty their molds to be within .002 in. of stated diameter, I don't stand to gain a whole lot (worst case: potentially only .001 in.), and given that I've already used this mold once, I'm going to take curator's advice and try it again, at higher temperature. I do have a thermometer, and the first run with the new mold was done from 700-725 degrees. I was getting good fills, and consistent, albeit "lite" weights. I'll run some this week-end in the 750-775 range and see how they come out before deciding what to do next.
Had this mold thrown balls .003 in. OVERSIZE...rather than UNDER...I'd not have been concerned, in fact might have considered it a PLUS. I like to shoot a tight combination, but don't want to make up the difference here, with too much patch.
This remains a work in progress. :thumbsup:
Stay tuned...

 

[mooman76]

Add a touch of tin and it will fill a little better and the balls will drop a little larger also with really making them noticeably harder.

 

[Zonie]

Some of this "not to size" can be due to the "shrink factor" the mold maker used to determine the size to machine the cavity to.

Molds are always made slightly oversize because the molten lead shrinks as it cools.

The amount of shrinkage depends on the purity or amount and type of alloy of the lead being used.
The temperature of the lead as it is being poured into the mold also has a lot to do with the amount of shrinkage the finished ball will have.

All of these things makes it almost impossible to make a mold that will produce an exact size.

 

[Don Steele]

Final chapter...for the moment.
I ran a small batch of 50 or so balls through the Lee mold yesterday. Melt temp was held at 775-780 degrees.
I picked up .001-.002 in on diameter, and a touch over a half grain in wt.
I'm having a 40 cal LH flintlock built, and all this casting has been to have everything ready when she arrives.
At this point...I'm going to wait for the rifle, and see how these balls shoot before doing anything else.
I have tin and if I'm not satisfied with the straight lead balls, I may give that idea a try...or just buy a better mold.
Thanks for all the thoughts. :hatsoff: I'll be posting the load development results when the rifle gets here. I already have some donated .400 balls to work with as well.
Once again...A Work In Progress.

 

[Pete G]

A couple of thousandths in a PRB can easily be much ado about nothing. Patch thickness can vary more than, even when cut from the same piece of cloth. Use the mold, cast plenty of balls and have fun.

 

[necchi]

A couple of thousandths in a PRB can easily be much ado about nothing.

I agree with that.
Consistency is the key,, even if they're a tiny bit small as long as they're the same it won't matter a hoot.
Don you mention you don't want to make up for the small ball with patch thickness,, well I'm pretty darn confident you'll be able to find a load combo with powder charge and lube properties that'll give ya a package that'll shoot better than most people can with the mold you have.

Give it a chance and work the other variables around the ball size, and don't forget you'll have a break in period with the new barrel before it really dials in. If you go looking to improve a load combo by changing ball size much before 200 shot's down the barrel,, you may well miss a fine combination with the current Lee mold.

 

[Don Steele]

Thanks for all the thoughts folks.
I'm at the point now to take the balls I have available from this mold, some .400's of unknown provenance that have been donated, and some that I will cast from a buddy's Lee .400 mold and wait patiently for my new rifle. I have 2 thicknesses of patch material already to test. I suspect I'll be busy well into the Summer on this project. :grin:
We haven't even begun discussing powder charges..!!
Anyone who has seen most of my posts here might notice that I'm a HUGE fan of Consistency. Almost to the point of being (justifiably) accused of being a bit anally retentive. OK...guilty as charged. Stay tuned...More to come once she is delivered.
It's always the journey. :thumbsup:

 

[nhmoose]

I will bet you can find no difference on a target.

Off a bench you will need a .400 or .401 and Teflon treated pillow tick patching. Over bore is the winners on the bench circuit.

Never heard of tefloned match patching? Go to the NMLRA and find out who is selling it.

Large balls win.