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Posted: 11/4/2013 8:03:13 AM EDT
| Question about resizing cast bullets for 40/10mm. The mold that we have is supposed to be .401 and that is the size die that is used. I checked some jacketed bullets and they are sized at .400. Would there be any advantage to resizing the cast bullets to .400? All of the commercial cast bullets are also .401. Just thinking that it might be easier to reload the cast bullets this way. |
| Leave them at .401, you generally want your lead at least .001 over nominal bore diameter. A slug of the barrel will give you precise bore dimensions, but what you have usually works fine. If you use tumble lube bullets, got to Castboolits.com for lubing info. On those, I use a mix of Alox and other stuff. Lube groove bullets are best tested with different lubes to get best results. |
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Cast bullets generally need to be 0.001 or more over bore size to keep leading down.
You want to slug your bbl, use a micrometer to measure the major diameter of the slug, and size your bullets about .001 over that. You will likely have horrible leading issues if you go to .400 dia. |
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Cast lead bullets .001 over is SOP. Sizing down smaller causes horrible leading in the bore.
With lead being softer than copper jackets they need that extra .001 to get a better grip into the lands. It also helps seal the bore preventing any gas leakage past the bullet. If you size them smaller they may not engage the rifling enough or have the sides (driving bands) stripped off making them act like a smooth bore musket ball, no rotation. Then the hot gas vaporizes the lead as it goes past the bullet and deposits it on the bore. The next round smears it in and deposits more and the cycle goes on till your barrel looks like a shotgun. A little extreme example but if you keep shooting without cleaning it out it will come to look like that. Your mold will likely produce bullets that are a little over the stated dimension requiring sizing to .401. If they were for a revolver they could be shot as-is with just lubing them. Since they are for a semi-auto gun they will probably be too big to chamber. I've shot 45 Colt bullets as-cast at .455 diameter in my SAA's without any problems. Lead bullets for 45 Colt are sized to .452 but the extra .003 did nothing but make a few a little hard to chamber. So, no. No advantages, only disadvantages and nightmares. |
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Thanks everyone for the replies. This kind of what I thought but figured 'no loss to ask'. Being the I am loading/shoots cast bullets out of Glock's and using after market barrels, I have noticed that I need to pay closer attention to these compared to the jacketed bullets.
Will continue to stay at .401. |
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