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Post by Bullshop on Dec 1, 2015 18:17:32 GMT -7
Question --- Are you sure about the bullet diameter of .260", For the 25-20 SAAMI is .257" diameter ?
answer --- That saami .257" would be for jacketed bullets. For best accuracy cast bullets almost always run .002” to .003” over groove diameter. A fast simple way to find the cast bullet diameter that should work best in your gun is to mik the inside neck diameter of a case fired in your gun. Something very close to that diameter is likely what will work best. This rule will not apply to revolvers. For revolvers the diameter that will most likely shoot best is the cylinder throat diameter or about .001" to .0005" under cylinder throat diameter. |
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Post by Junior on Dec 2, 2015 21:48:59 GMT -7
Something to think about. Even though most of the time cast Bullets will shoot better slightly over size, it's not always possible to do so. I currently have a 308 that I chambered by hand purposely with a very tight chamber, and it will not chamber rounds that are loaded with anything larger then .308" bullets. And it's not always custom guns that are like that. I used to own a Stevens model 200 in 7mm/08 that the factory chamber was so tight on I had to turn necks on cases to shoot jacketed bullets, and even then the necks were thin enough I only got 3 firings top on cases. Turned thin enough to get a .002" over sized bullet to chamber, they were only good for one shot.
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Post by Bullshop on Dec 3, 2015 7:15:11 GMT -7
What you say is true but as a general rule cast bullets are usually run .001" to .003" larger in diameter than their jacketed counterparts.
There are always exceptions to rules.
Another exception to this general rule I have now through experience come to expect is in old Winchester rifles. These rifles were built differently for a different type of ammo than more modern guns. I have many times experienced with these old Winchesters that they will not chamber a cartridge loaded with a bullet larger in diameter than the groove diameter of its barrel and often give issue even with bullets sized to groove diameter.
The reasons I suspect have to do with the properties of black powder as a fuel and fairly soft cast bullets of binary alloys of lead and tin.
Another general rule that is acceptable even with old Winchester rifles is to mik the inside diameter of a case neck that has been fired in the rifles in question. This diameter is the largest that you can expect to chamber freely and will likely be what shoots best with a cast bullet.
You may still encounter chambering issues but they will not be due to bullet diameter but most likely due to bullet nose shape/size not being compatible with chamber throat/lead.
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Post by Junior on Dec 3, 2015 8:13:17 GMT -7
True. Like on that 7mm/08 I had the inside of the neck miked under groove diameter. All I was pointing out is that there are exceptions to the .002" over rule.
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Post by todddoyka on Jan 11, 2016 12:19:33 GMT -7
i would like to get a 38-55 for my encore in a MGM barrel. although its a 38 cal, the 38-55 that i want will be a .375" barrel(i asked them, and their bores are what they say it will be). i did check on my 444 marlin(MGM BARREL) and it slugged out at .429".
now if i get my 38-55 and slug the barrel out and it comes to .375". do i go the .2 - .3" or do i go with a 235gr ranch dog that goes .379" or .4" over?
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Post by Bullshop on Jan 11, 2016 13:05:25 GMT -7
The simple answer is "it depends" Normally I would recommend at least .001" or maybe .002" over your groove diameter.
The "DEPENDS" part has to do with how tight the neck is in your chamber, how thick the brass is that your using, and to some extent the throating or lead into the rifling.
The Ranch Dog TL- tumble lube designs all seem to run on the fat side so I do size/lube them as any other in a lubrisizer.
If your barrel is tight necked and your brass on the thick side in the neck the Ranch Dog bullet unsized may not chamber in your barrel.
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