Does this make sense? SLugging and sizing

[whelen fan]

So I bought a M&P9 in order to shoot cast boolits. Slugged the bore and wouldn't you know it, it doesn't have a groove on the opposite side so I can't measure with my micrometer. I have a 356 sizing die that the slug fits into by pushing it in with my finger. Easy to do.

Now does this make sense? Since it fits in "easy" it must mean that my bore is smaller than what the boolits will get sized to in my 356 sizing die. Which would give me the 1 thou or so over bore diameter.

The mould is a lee 6 banger 356-120TC and lead is range pickup so a mix of jword and cast. The mould casts at .3565 avg.

Thanks

[Gtek]

Find a piece of thin shim stock, .002" to .004" works well, tweek it around a pencil or dowel before measure helps. Measure shim for confirmation with a good micrometer. Wrap bullet 180 degrees with shim, measure outside, subtract shim x2 and that is how big your boolit is. Gtek

[Mal Paso]

Size Dies aren't always the dimension stated for a couple reasons. Some manufacturers make the die smaller to allow for lead spring back and some manufacturers can't hold tolerances.

[williamwaco]

OK,

Back to basics.

Slugging the barrel is usually a waste of time.
Don't worry about it.

If you have a .357 sizing die, size a couple .357, make a couple of dummy rounds and see if they will chamber. If they do, use that die. If they don't, use the .356.

If you have only the .356 die, size a couple .356, load up 10 or 12 rounds and try them at the range. If they shoot well and don't lead, use them.
If you have poor accuracy, tumbling, or leading, get a .357 die.

Yes, you can re-size your sizing die from .356 to .357. There are several threads here on how to do it.

[SciFiJim]

OK,

Back to basics.

Slugging the barrel is usually a waste of time.
Don't worry about it.

If you have a .357 sizing die, size a couple .357, make a couple of dummy rounds and see if they will chamber. If they do, use that die. If they don't, use the .356.

If you have only the .356 die, size a couple .356, load up 10 or 12 rounds and try them at the range. If they shoot well and don't lead, use them.
If you have poor accuracy, tumbling, or leading, get a .357 die.

Yes, you can re-size your sizing die from .356 to .357. There are several threads here on how to do it.


William,
Thanks for the reminder. Sometimes we get caught up in the minutia and forget that often the easiest thing is to just try it and see if it works.

[cbrick]

Size Dies aren't always the dimension stated for a couple reasons. Some manufacturers make the die smaller to allow for lead spring back and some manufacturers can't hold tolerances.

Off topic but . . . the biggest reason dies size differently than as marked is alloy variation. Differing percentages of Sb result in different as sized diameters. Most of the die makers do a pretty decent job but with everybody out there using different alloys it must be turning their hair grey.

Rick

[Larry Gibson]

You can easily measure the slug as Gtek mentions. On the other hand, before the advent of the internet I shot thousands of 120 gr 356402s and 358242s sized at .356 because that's what they were supposed to be sized to for the 9mm. I used Lyman's graphite lube and then Javelina lube. Shot them out of HPs, M39 and M59s, Lugers, P38s, other sundry handguns along the way and a few subguns. Never had any leading and all were as accurate as the gun was going to be.

Then I read all about "proper" sizing on the internet and got a .357, .358, .359 and .360 sizer. Tried them all with those bullets and Lee's 356-120-TC and you know what? I get no leading and accuracy is as good as the gun is going to shoot (with me shooting it anyways).....so.......

I suggest you just size a few of your your Lee 356-120-TC cast bullets (25 -30 should tell the tale) with the .356 sizer, use a good lube (BAC or a 50/50 NRA formula lube always works for me) and load over 3.5 - 4 gr of Bullseye (WST, 700X, HP38 or 700X works as well) if you have it and shoot them. See if there is any appreciable leading. If not and they are accurate you are "good to go".

Larry Gibson

BTW; I am not suggesting that "proper" sizing of cast bullet is not necessary in some instances for best accuracy and no leading. What I am suggesting is that there is a range of acceptable sizing that works. If your alloy is good, the lube is good and you load correctly you shouldn't get any leading with .356 sized cast bullets in a quality 9mm pistol. Your pistol also will probably not tell any differnce in accuracy between a .356, .357 or .358 sized cast bullet. Try what you have, there is no reason it won't work just fine.

[fcvan]

When I first started casting for 9mm, I bought a Lee 356-125 2R, and a Lee .356 push through sizing die as I was pan lubing. Upon first firing through my S&W 459, I experienced leading and poor accuracy. I decided to shoot as cast and they shot clean and accurate.

Back in the 1970s, Dad taught me about properly expanding the case so that it does not size down the boolit. I took to belling the case mouth to where it would accept the boolit base and seat without shaving. I set my crimp just to remove the belling and did the plunk test with the barrel.

When I finally bought a Lyman 450 lubrisizer, I bought a .358 sizing die. The boolit is slightly shined by the die. I cast and shot many thousands of rounds before I ever slugged a barrel or measure the boolit. As the weapon chambered and fired flawlessly I did not feel the need to measure in the classic sense. I measured using the plunk test, I pushed boolits through the cylinders of my wheelguns, but mostly I just loaded and shot.

As the post above said, 'just try it and see if it works.' With all of the great advice available here on Cast Boolits you should be able to tweak to perfection with repeatable success. Oh ya, I have shot that boolit generally over 5 grains of Unique with various types of lube. For years it was Javalina, and of late White Label BAC. I even made my own loob using a recipe from this site. The only time I ever experienced leading or poor accuracy since my first efforts, was when I bought a .357 sizing die to try it out. My 9mm patterned and key-holed. I traded that die away and went back to .358 sizing.

I set my seat/crimp die using a factory round. I backed out the seating stem and screwed the die body down finger tight on the case mouth, then screwed down the seating stem. When I use a different boolit, such as the 356-120 TC or the 358-105 SWC, I reset the die so that the rounds cycle and fire and make a dummy round so I can duplicate at a later date. Of late, I am shooting the heck out of the 120 TC boolit in my 9mm weapons. As cast from range scrap, the boolit is dropping .3585 at 125 grains. I have even loaded this boolit for my .357 Mag with a plain based gas check. Good fun.