Lee sizing bushings .

[flynth]

I did a batch of Lee 312-160, PC-ed and sized with .311 bushing couple days ago, measured today at 0.3103

I went through the same surprise with Lee sizing dies (steel, not carbide). I found my Lee dies were under size by around 6-8 ten thousand of an inch so slightly less than a thou. I also found out they size correctly if one uses Lyman #2 (locally made, but pretty close to the original). Using 20 to 1 alloy I found the boolits under size as you did.

Using an expandable cylindrical lap and a grinding compound is one way to go. If you choose to go down this route I suggest no bigger than 10 micron grinding paste (grit no 1000 and more, if you can find 5 micron that's better). It'll take a little longer but you can always remove more, while putting it back on is not so easy.

However, to open my dies I used automotive wet/dry 1000 and 2000 grit sandpaper with some thin mineral oil. I used a lathe to spin the die, but If you haven't one you could use a wooden dowel. Size one end so you can hammer it half way into the die from the top (bottom 40% does all the sizing, upper part is just clearance hole). Chuck the other end in an electric drill and you have a way to spin the die.

Then take a piece of 1500 (1000 if you are very careful) auto paint sanding paper, roll it around a wooden pencil in a direction so die rotation tightens it. Spin the die, put the pencil with sandpaper in and now is the most important part. Do not allow the pencil to remain in one place. Move it in and out while rotating it. If you just press it in one spot you'll open the die unevenly. At the drill set to 1500rpm give it no more than 2~3 seconds at most for the first time. When you pull the pencil the sandpaper should be grey. Clean the die very thoroughly, lubricate and try sizing few bullets of your chosen alloy. Measure and decide if you want to open it some more. Those 2~3 seconds should open it up at least 2~3 tenth thousands of an inch. Ideally you catch it when it is a tenth or two too small, then you use 2000grit for the last bit (also no more than 3 seconds).

Please note doing it only makes sense if you can reliably measure to few tenths. If the best measuring accuracy you can repeatedly get is one thou (nothing uncommon) you may get a nasty surprise in a form of: the die is too small, next time you measure it is too big

All those random movements combined with small grit average out and result in not going out of round if you open no more than up to a thou. If you're opening more a lap is much better.

[Eddie1971]

I've just started casting recently and had been purchasing my equipment whenever available. I've decided to go with PC and sizing my bullits with APP and Lee bushings; made a small batch sized them with 0.357 bushing and they all measure 0.356". Today came my pin gauge set and all of my 8 bushings (356-358, 401, 402, 310, 452, 454) are undersized by at least 0.001" Have couple NOE bushings and those are spot on. So what would you do ? Contact Lee and try to exchange, use as is, knowing they are undersized ?

I found the exact same thing with my Lee sizers. I got so mad when a custom one I ordered was the same way that went to the NOE sizers and never looked back. When I look at my shelf and see all the Lee sizers I don't use it infuriates me. Wish I knew about the NOE kit earlier....you live and learn I guess!

[kayala]

I still use mine, just mindful of their true size, but I agree NOE sizers are awesome.

[243winxb]

I was using MP mold (357-125FB) . I didn't measure as dropped (from mold.) but PC-ed and sized them with .357 bushing. Alloy is "hardball" from rotometals (92-6-2), as I've said none of those sized bullets sprang back to .357. Why would alloy matter for sizing, I've thought if I size to .357 it should be .357 whether it was pure lead or BNH22. Am I wrong ?

The diameter of the as cast bullets should be checked as soon as a few cool. My Lyman 45 acp mold runs right on the edge of .452" Linotype needs added, at times, to enlarge the diameter. The antimony makes for a larger bullet diameter, more then tin.

[Conditor22]

Measure your pin gauges with a micrometer.

Polish you lee bushing to where it sizes boolits to the diameter you want with the alloy you are using.

[kayala]

Measure your pin gauges with a micrometer.

Polish you lee bushing to where it sizes boolits to the diameter you want with the alloy you are using.

I did spot check few pins all very spot on (to the best of my measuring abilities) and as I've said I use Lee anyway, just keep in mind that they are 0.001" smaller as well as numerous NOE bushings, which accept pin they are marked for.

[garandsrus]

I have made quite a few sizing dies of all types. The actual diameter of the hole itself doesn’t matter. The diameter of the bullet that is sized does. Measure the sized bullets instead of the size of the hole and open the die to produce the bullet diameter you want. The hole in the sizing die has to be smaller than the target bullet diameter. If I can pass a .359 minus pin through the die, the bullet will be greater than .359 after it is sized.

For what it’s worth, it takes me a lot more than 2-3 seconds of 400 grit sand paper to enlarger a hole .0002-.0003. It takes longer than that just to push the sanding rod through the die and pull it back through. After a pass through the die the sandpaper will need to be replaced as it will be loaded up and appear grey, as was mentioned.

[kayala]

If I can pass a .359 minus pin through the die, the bullet will be greater than .359 after it is sized.

That’s what Lee customer service guy told me - they account for “spring back”

[Yooper003]

Not sure if any of the guns that I cast ,size, powder coat for can tell the difference in .001.