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**Unclenick** · February 20, 2013, 10:52 AM

Bullets are actually pretty tight. You can choose either .308 or .3085 or .309 bullets for .30 Caliber, depending what your bore likes. GS Custom in South Africa lathe turns their bullets and claims to hold diameters to within 0.0002", and runout is probably a quarter of that. So it's a precision machining operation. Whatever diameter tolerance you can hold, though, consistency through the run is more important than absolute value. Once you develop a load you don't want to have to change it, bullet to bullet, based on diameter fluctuations. It is unlikely to be dangerous for bullets to fluctuate half a thousandth, but could conceivably mess with accuracy by shifting you off a sweet spot barrel time.

The materials choices are numerous. Soft steel jackets with a 0.002" copper wash are pretty standard in some foreign military ball ammo. Barnes used to make some brass solids. They're discontinued (don't know why), but one of the gun writers said he thought they were among the most accurate .308 bullets he'd ever used. Can't recall who. I got a few boxes from an estate sale that are 165 grain spitzers. A whopping (for a flat base bullet that weight) 1.385" long, but that turns out to be a good length for a 10" twist barrel in a bullet that weight. A little long for a 12" twist. The trusty Mitutoyo's say they are all 0.30740" to .30755", so basically a half thousandth under groove to lessen the swaging effort a bit.

The more modern solid designs have ribs the full groove diameter to lessen the effort of engraving them with the rifling to try to bring it down to that of a regular jacketed bullet. I don't have any to measure, but pick up some Hornady solids with those ribs to get a place to start. Their like having driving bands on an artillery shell. Getting some leaded brass for that might go well.

The trick is to develop the load with whatever the material is.

Do watch out for bullet length. Being less dense, the solids tend to be long. Length is more important to bullet stability than weight of velocity, and you have to have a fast enough barrel twist for it. The stability estimator at the bottom of this page will let you check your designs. Just don't let the Stability number in the result get below 1.4 and you should be OK.

Barnes brass with a jacketed .45 RN to show the color difference better:

February 20, 2013, 10:52 AM	#10
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	Bullets are actually pretty tight. You can choose either .308 or .3085 or .309 bullets for .30 Caliber, depending what your bore likes. GS Custom in South Africa lathe turns their bullets and claims to hold diameters to within 0.0002", and runout is probably a quarter of that. So it's a precision machining operation. Whatever diameter tolerance you can hold, though, consistency through the run is more important than absolute value. Once you develop a load you don't want to have to change it, bullet to bullet, based on diameter fluctuations. It is unlikely to be dangerous for bullets to fluctuate half a thousandth, but could conceivably mess with accuracy by shifting you off a sweet spot barrel time. The materials choices are numerous. Soft steel jackets with a 0.002" copper wash are pretty standard in some foreign military ball ammo. Barnes used to make some brass solids. They're discontinued (don't know why), but one of the gun writers said he thought they were among the most accurate .308 bullets he'd ever used. Can't recall who. I got a few boxes from an estate sale that are 165 grain spitzers. A whopping (for a flat base bullet that weight) 1.385" long, but that turns out to be a good length for a 10" twist barrel in a bullet that weight. A little long for a 12" twist. The trusty Mitutoyo's say they are all 0.30740" to .30755", so basically a half thousandth under groove to lessen the swaging effort a bit. The more modern solid designs have ribs the full groove diameter to lessen the effort of engraving them with the rifling to try to bring it down to that of a regular jacketed bullet. I don't have any to measure, but pick up some Hornady solids with those ribs to get a place to start. Their like having driving bands on an artillery shell. Getting some leaded brass for that might go well. The trick is to develop the load with whatever the material is. Do watch out for bullet length. Being less dense, the solids tend to be long. Length is more important to bullet stability than weight of velocity, and you have to have a fast enough barrel twist for it. The stability estimator at the bottom of this page will let you check your designs. Just don't let the Stability number in the result get below 1.4 and you should be OK. Barnes brass with a jacketed .45 RN to show the color difference better: __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle Last edited by Unclenick; February 20, 2013 at 10:59 AM.