Author Topic: Revisiting Cast Lead in the 8mm  (Read 584 times)

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Offline Dan Chamberlain

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Revisiting Cast Lead in the 8mm
« on: November 12, 2004, 11:15:07 AM »
I slugged my bore on the 24/47 and found the measurements to be:

.312/.324

Most of the gas check molds I've seen are listed as .324!  Do common bullet alloys experience any obturation during the firing process where they flatten a bit and fill in the empty space?  My softer muzzleloading bullets do.  

With a bore such as I have measured, will the .324 mold work...or will I have to go with the larger .329 mold made for a different rifle all together?  This mold is not a gas check mold and is significantly heavier.

Thanks

Dan C

Offline jh45gun

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Revisiting Cast Lead in the 8mm
« Reply #1 on: November 12, 2004, 02:28:24 PM »
From what I have read they will upset and the faster the velocity the more they will upset. Shoot too fast and the nose goes haywire and accuracy suffers. At least that is like I said what I have read. I have not had that much expirience to vouch for that but sounds reasonalbe. I use a lee cast  bullet that I have not measured yet but is rated at 323. My bore  measured 324 so I figure I should be ok. I would try the 324 rated one first. Jim
Said I never had much use for one, never said I didn't know how to use it.

Offline Leftoverdj

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Revisiting Cast Lead in the 8mm
« Reply #2 on: November 12, 2004, 04:14:24 PM »
Cast bullets don't slug up over smokeless powder. You gotta start out with the bullet at or over groove diameter, preferably throat diameter. Fortunately, most moulds cast a bit over nominal diameter. Your nominal .324 mould probably casts at .325-.327 depending on alloy. Only way to find out is to cast some up and see. My Lyman 323470 casts at .325.

There are a couple of tricks that let you increase bullet size a bit. High antimony alloys cast fat. It's fairly simple to lap a mould out a couple of thous. Shimming the face of the blocks with aluminum tape will increase diameter and the slight oval hurts nothing.

I'd suggest that you start out with Lee C324-175-R. It's cheap and should work, maybe as is, maybe with some tinkering. Lyman has a .325 sizer as a stock item if you already have a lubrisizer. Lee only has .323 and .329 but they will make you a custom one for $25. I'd just buy the .323 and lap it out to .325 myself. Lee's C329-205-1R probably will not work for you. Its nose engraves in my 8mm and that one measures .315 land to land. Sizing the body does not help with the nose.

After you get a feel for what you are doing and decide what you like and dislike about the Lee, you can go to www.mountainmolds.com and spec out what you want for a semi custom mould. The program is very easy to use and lets you see what you have designed. Prices are only slightly over Lyman and RCBS.
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Offline jh45gun

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Revisiting Cast Lead in the 8mm
« Reply #3 on: November 12, 2004, 06:37:13 PM »
OK Lefty how do you go about lapping out the sizer. I just bought one so I can seat gas checks on my bullets and it either was the 323 or the bigger one. I went with the 323. Due to not wanting to have them custom make one for me at a higher cost.  I suppose be fore I worry about that I will size and shoot some first and see how they shoot. Jim
Said I never had much use for one, never said I didn't know how to use it.

Offline Leftoverdj

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Revisiting Cast Lead in the 8mm
« Reply #4 on: November 13, 2004, 05:31:31 AM »
Several methods to lap, JH. The easiest and the one I mostly use is to lube some cull bullets with fine valve grinding compound and shuck them through. I use Clover 320 grit to start and four or five cull bullets and when the first one comes out the top, I run it through again. When each bullet has gone through five or six times and they are going through easily, stop, clean the die and the post, and run a nekkid bullet through. Measure that bullet to see how far you have gone. If you're close to where you want it, lube a few more culls with 600 grit to polish.

Some folks wrap a piece of auto body paper around a dowel and just roll the die across a mouse pad using the dowel as an axle and applying some downward pressure. I've never done it that way, but many have.

I have used the dowel and the sand paper with the sizer in a lathe. Never opened up a sizer more than .002 and suspect that .003 would be the absolute most I would ever try for.

You can also open up moulds with the same compounds if you have a means of getting a machine screw centered and straight into a cull bullet to use as a shank. You coat the bullet and turn it by the shank in a tap wrench or the like while gradually applying pressure to the mould handles. I have a very neat gadget I got from Brownell's that is just a drill chuck on a wooden handle that works very well for this. Don't try using power for this unless you have a lot of experience and a very solid set up.

If you just use 600 compound, that's the best method I know to get a baulky mould to drop bullets freely. When you do that, you are not trying to remove any metal but the tiny burrs that the fresh castings are hanging up on.
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Offline Duffy

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Revisiting Cast Lead in the 8mm
« Reply #5 on: November 13, 2004, 06:48:39 AM »
A ink eraser works pretty good on the little burrs along the edges too.

Offline jh45gun

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Revisiting Cast Lead in the 8mm
« Reply #6 on: November 13, 2004, 01:48:48 PM »
Thanks for the info Lefty.
Said I never had much use for one, never said I didn't know how to use it.