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Bart B. · March 6, 2013, 07:41 AM

It's interesting to me how folks measure accuracy.

To some, it's the smallest group ever fired. Could be the smallest few-shot group fired with a given load. Might be the many-dozen shot group with the smallest mean radius of shot holes from group center. Remember that every rifle and ammo combo holding smallest-group records rarely, if ever, shoots another group that size. All the rest are bigger; how much is difficult to know 'cause benchresters typically keep them secret.

Kraig's reference to the "Secrets of the Houston Warehouse" is a good example of several few-shot groups. They are impressive as are anything that shoots in the zero's (groups under 1/10th MOA).

I've seen 10-shot groups fired at Sierra Bullets' plant in California from .308 Win. chambered rail guns with 168 and 190 HPMK's shot at their 100-yard indoor range were in the zeros, too. With a good batch of jacket material and lead cores, groups in the zeros would happen time after time after time for several dozen tests in a row while one lot of bullets were being made. In contrast to those shot in that Texas warehouse, Sierra's came from full length sized cases shot in SAAMI spec chambers; no tight necks at all. When the final machine making those bullets was spittin' 'em out and 10 at a time were grabbed, stuffed into cases and immediately fired. As long as the 10-shot test groups were well under 2/10ths inch, that run of bullets would be set aside for special packaging. Sierra's specs for their 168 and 190 HPMK's was test groups had to average .250" at 100 yards; some would be up to about .350"

Then there's the test at 600 yards made back in 1971 by one of the Nat'l Champs testing his 26" Hart barreled Win. 70 wood stocked .308 with 185-gr. FMJBT bullets as perfect as he could find. With the rifle clamped in his machine rest (equal to any benchrest rail gun so shot), he fired several 10-shot groups. His WCC58 cases were all full length sized and stuffed into a SAAMI spec standard chamber. All the groups were 1.5 inch or smaller; smallest about .7 inch. At 600 yards, that's .117 MOA to .250 MOA. Then he fired a 40-shot group with that ammo into 1.92" at 600 yards from that rifle.

Readers can decide for themselves which is "best" accuracy; several 5-shot groups from neck sized cases in the zeros at 100 yards fired indoors or several 10-shot groups from full length sized cases in the ones and twos fired at 600 yards.

It's happens that some folks using the tools that others use to get fantastic results just doesn't happen with their using them. As the variables in a given tool are extremely small, I don't think it's the tool's fault.

Benchresters did not change over to full length sizing dies to shoot the tiniest groups. Their smallest groups fired with neck sizing and full length sizing their fired cases stayed the same. What changed was the size of the largest groups fired. What's more accurate, something that shoots from 1 to 6 units of measurement or 1 to 4?

March 6, 2013, 07:41 AM	#12
Bart B. Senior Member Join Date: February 15, 2009 Posts: 8,927	It's interesting to me how folks measure accuracy. To some, it's the smallest group ever fired. Could be the smallest few-shot group fired with a given load. Might be the many-dozen shot group with the smallest mean radius of shot holes from group center. Remember that every rifle and ammo combo holding smallest-group records rarely, if ever, shoots another group that size. All the rest are bigger; how much is difficult to know 'cause benchresters typically keep them secret. Kraig's reference to the "Secrets of the Houston Warehouse" is a good example of several few-shot groups. They are impressive as are anything that shoots in the zero's (groups under 1/10th MOA). I've seen 10-shot groups fired at Sierra Bullets' plant in California from .308 Win. chambered rail guns with 168 and 190 HPMK's shot at their 100-yard indoor range were in the zeros, too. With a good batch of jacket material and lead cores, groups in the zeros would happen time after time after time for several dozen tests in a row while one lot of bullets were being made. In contrast to those shot in that Texas warehouse, Sierra's came from full length sized cases shot in SAAMI spec chambers; no tight necks at all. When the final machine making those bullets was spittin' 'em out and 10 at a time were grabbed, stuffed into cases and immediately fired. As long as the 10-shot test groups were well under 2/10ths inch, that run of bullets would be set aside for special packaging. Sierra's specs for their 168 and 190 HPMK's was test groups had to average .250" at 100 yards; some would be up to about .350" Then there's the test at 600 yards made back in 1971 by one of the Nat'l Champs testing his 26" Hart barreled Win. 70 wood stocked .308 with 185-gr. FMJBT bullets as perfect as he could find. With the rifle clamped in his machine rest (equal to any benchrest rail gun so shot), he fired several 10-shot groups. His WCC58 cases were all full length sized and stuffed into a SAAMI spec standard chamber. All the groups were 1.5 inch or smaller; smallest about .7 inch. At 600 yards, that's .117 MOA to .250 MOA. Then he fired a 40-shot group with that ammo into 1.92" at 600 yards from that rifle. Readers can decide for themselves which is "best" accuracy; several 5-shot groups from neck sized cases in the zeros at 100 yards fired indoors or several 10-shot groups from full length sized cases in the ones and twos fired at 600 yards. It's happens that some folks using the tools that others use to get fantastic results just doesn't happen with their using them. As the variables in a given tool are extremely small, I don't think it's the tool's fault. Benchresters did not change over to full length sizing dies to shoot the tiniest groups. Their smallest groups fired with neck sizing and full length sizing their fired cases stayed the same. What changed was the size of the largest groups fired. What's more accurate, something that shoots from 1 to 6 units of measurement or 1 to 4? Last edited by Bart B.; March 6, 2013 at 07:49 AM.