Star size die question- help me figure this out please

I bought a Star sizer on ebay a few months ago and I am just now getting around to messing with it. It came with a sizing die marked .358, which is partly why I bought this particular one- because I plan on casting and shooting .38/.357.

So here's the situation: To verify that it is indeed a .358 sizer I pulled out the plug guages and this thing will pass only a .356+ (go) guage, nothing more. Did I get duped or is there more going on here like lead "springback" that can explain why this is the correct ID?

Please let me know something before I apply the .358 reamer to it! Thanks.

Edit: Before someone replies with the bright idea to puch a bullet through and measure it, let me explain that I do not have an instrument on this premisis that I trust to make a measurement this precise. Crappy reloading calipers I don't think will do it and I don't have a micrometer.

So just size them and believe that they are right, you can't measure them anyway, so how will you know? In other words, buy a micrometer, there was one for 15.00 for sale right here yesterday. Different alloys will have different springback.

measure it with your reloading calipers who cares if it's off by .00001
if they don't shoot well in your revolver then start fixing things.

i'd lap the sizer out before reaming it b.t.w.

Take a few to a store that has quality micrometers and ask to see one to see if you want to buy it. Measure your bullets and maybe you will want to buy it.

Ordered micrometer yesterday. Still I wonder how this die will produce .358 bullets, but we will see.

Interesting that this comes up today...just went through this very thing with Magma...when you order a sizing die from Magma for .358 (or anything else) they will make the die the size for a .358 BULLET using Lyman #2 alloy...in other words it will be about .003 smaller than .358..(their words) they will however make them however you want when ordering and will also "ream" out the one(s) you have if you send it with a note telling them what you want...I just sent three back to them to have opened up and yesterday received a new .431 that I had ordered (after this discussion with them and told them I wanted an actual .431 die) that sizes bullets to .4308...so I think I'm done with Magma...however that is pretty close..

You might check with lathesmith as to dies, he does a great job with them. I have a half dozen of his dies and love them. I purchased a number of the nuts with the set screws only to find I use the die for multiple boolits and the locking nuts would require a number of punches. I just have a file with the height offset in it and set the punch height with calipers.

The machined diameter of the bore accounts for springback of the boollit and will be smaller than desired boolit dia.

Similar to forming parts on a brake, need to over bend to obtain desired angle, and this varies with mat'l.

This just in: brand new micrometer says .3578 on a slug pushed through the die. The die will pass a .356 (+.0002) go guage. Yep, springback accounts for the difference.

Quote:

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Originally Posted by runfiveslittlegirl

measure it with your reloading calipers who cares if it's off by .00001

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Not correct, even brand new Mit calipers are listed as plus or minus .001". That means as much as .002" is possible. Caliper were never meant or designed for precision measuring so the OP is correct in not doing it.

Quote:

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Originally Posted by claxton

This just in: brand new micrometer says .3578 on a slug pushed through the die. The die will pass a .356 (+.0002) go guage. Yep, springback accounts for the difference.

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hehe . . . Wait until you change alloys and measure the new boolits. Antimony percentage will determine final sized diameter. But you did do it correctly, glad you got the mic before altering a perfectly good sizing die.

Rick