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Discussion Starter · #1 ·
For my cast rifle bullets that are gas checked (6 & 7mm + .308") I try to make my melt hard to keep down bore leading. On my M336 30/30 with micro-groove I was told to try .310" for more accuracy. Both of my sizing dies for 30 caliber are .309". Can you increase velocity enough to fill out the bore with a gas check or should the melt be softer for this to happen? I seem to get my best accuracy at around 2000fps or higher. Does this indicate that my bullets are being kicked up to fill the bore or just what my rifle likes? Is this the right place to ask about cast bullets? I didn't notice any cast bullet forum.

If I get into heat treating bullets more, I'll need to get some oversized sizing dies for my Lyman lube and sizer I guess, but haven't got that far yet. I've been told that sizing makes your cast bullets a little softer but you need to lube them and clamp on a Hornady gas check. BM

Bill
 

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Blue Moon:

If you have some way to measure the hardness of the bullets you are casting, you can use Veral Smith's formula:

BHN (Brinnell Hardness Number) X 1,422 = chamber pressure required to obturate the bullet - "fill out the bore" as you describe it. Whether your bullet bumps up or not depends upon the pressure of the load and the hardness of the alloy. A full power .35 Remington load at 33,500 psi supposedly needs a bullet around 23 BHN or softer to obturate.

Actually, most loaders go about it the other way-they figure the pressure needed to obturate the bullet is a limit, and they stay below that so the bullet does not obturate. Most find that if the bullet fits properly any deformation upon firing is to be avoided. Wheelweights definitely fill out the bore in my own rifles using full power ammo, but accuracy will hold up for a while even though the bullet is almost plastic at the higher pressures. Even if the bullet is obturating, it is usually better to avoid overdoing things. My wheelweight bullets shoot better at around 2000 fps than at 2200-2300, and accuracy holds up much longer. The barrel leads less.

A more accurate test is to determine just what you want the bullet to do. If it is a bore riding design, does the nose of the bullet actually ride the bore? If it does not, guidance for the bullet in the barrel is not what it could be, and accuracy suffers. All body, non bore riding designs like the Louverin type usually do better in Microgrooves, but if your bore rider fits it can and will shoot very accurately. The RCBS 200 FN rides the bore in my own Microgroove .35's and it's almost difficult to find a load that won't shoot well, even full power loads.

I use wheelweights with about 0.75% tin added for deer hunting, and they work very well. This is as cast, unhardened. With judicious tempering in the oven, I can reach BHN 33. My wheelweights go around 12 BHN as cast and allowed to age for a few weeks. I shoot mostly the unhardened wheelweight alloy in the RCBS 200.

Stick the nose of the bullet in the muzzle and see if there are any engraving marks if you are using a bore riding design. If it does not show any engraving, you might consider casting out of a high tin alloy like linotype. This will fill out the mould better and give a little larger bullet, which may increase the diameter of the nose to the point where it rides the bore.
 

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Blue Moon,
You can also lap out one of your sizer dies to .310 or .311. Go to www.castpics.net for info on how to do this. You use the same method as they use on Lee dies. I use my lathe but other people have a hand method they use. Some dies are harder than others and take a little longer. The push rod being .001-.002 undersized isn't a big deal. The main thing is that the bullet is larger than the bore by .001-.002. Mark
 
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Discussion Starter · #4 ·
Thank you both for your advise. I'm not sure of the hardness of my melt. I use ww's, range scrape, some 95% tin-5% antimony lead free solder and a handfull of magnum shotgun shots 6% antimony. I bought the new Lee hardness tester for lead but have not tinkered with it enough to have much confidence in it yet. I think my melt is pretty hard because of the very small leading that comes from my 06 and 6 and 7mm. I have a Lee and Lyman .309" sizer and really need to know what my bullets are coming out of the mould at. I've never really payed that much attention to it until I got into casting more and wanted more accuracy. I've mostly used the lubers to clamp on gas checks and, for the Lyman, lube. BM

Bill
 

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If you don't want to lap you can get the diameter you want from Lee, they will do whatever size you want for $25.
 

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www.beartoothbullets.com
Try this web site. They have a cast bullet section in their shooters forum for discussing shooting and making cast bullets. The above answers are very good, but you might get a few more suggests and options at Bear Tooth Bullets.
 
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