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Old November 29, 2019, 11:35 AM   #1
Bart B.
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"If I do my part. . . ...

A common reason for shooting a few shots into a sub caliber group. Sub caliber groups typically have extreme spreads less than bullet diameter; often called a "one hole" group.

What does that mean?

Last edited by Bart B.; November 29, 2019 at 11:42 AM.
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Old November 29, 2019, 01:14 PM   #2
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Sub caliber groups typically have extreme spreads less than bullet diameter; often called a "one hole" group.

What does that mean?
Sub caliber means just what you said, the spread between centers of the farthest apart bullet holes is less than the diameter of the bullets fired. Its one hole.

However, a "one hole group" can be much larger than "sub caliber". A group where all shots overlap leaving one hole in the target is a one hole group.

I've shot a number of one hole groups where the maximum spread distance (center to center) was more than a single bullet diameter but there was only one hole in the target as all holes overlapped. I've done it with a 1911A1, for example, 5 shots all overlapping. One ragged hole, but not a sub caliber group.
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Old November 29, 2019, 02:07 PM   #3
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Means there's a bench rest guy at work. "Less than bullet diameter" groups, I think, has more to do with how the BR guys measure groups. Never have figured out how one can shoot a .0077"(current, 5 shot, 100 yard, BR record.) diameter group with a .308" bullet. https://kriegerbarrels.com/smallestgroup
One hole groups is just that. All shots make one hole. Not "no distinct separate bullet holes", but all holes are touching. The gun rag writer's ideal of a clover leaf group with 3 shots.
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Old November 29, 2019, 03:53 PM   #4
Bart B.
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Sub caliber groups are measured with

http://www.neiljones.com/html/target_measuring.html

2 caliber diameter circles on glass are aligned on the 2 widest shot holes, accurate to .0001 inch. The centers of shot holes are the reference, not the outside edges.

http://bulletin.accurateshooter.com/...il-jones-tool/

Last edited by Bart B.; November 29, 2019 at 04:01 PM.
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Old November 29, 2019, 04:53 PM   #5
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Quote:
Originally Posted by T. O'Heir View Post
Means there's a bench rest guy at work. "Less than bullet diameter" groups, I think, has more to do with how the BR guys measure groups. Never have figured out how one can shoot a .0077"(current, 5 shot, 100 yard, BR record.) diameter group with a .308" bullet. https://kriegerbarrels.com/smallestgroup
One hole groups is just that. All shots make one hole. Not "no distinct separate bullet holes", but all holes are touching. The gun rag writer's ideal of a clover leaf group with 3 shots.
"...If I do my part..." Is about the shooter. No coffee jitters, good concentration, good breathing, sight picture and trigger control.
It has to do with measuring groups by the widest distance from the centers of the bullet strikes...nothing to do with bullet diameter.
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Old December 6, 2019, 08:35 AM   #6
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I was pleased to shoot what could be considered a "bullet-diameter" 3-shot group yesterday with my factory Rem 700 ADL, .223 in factory dress, Leupold 3-9X, but pillar-bedded/floated barrel, using unfired new Starline brass and Sierra bullets in 30 degree weather, off an old Hoppe's rest at our club range in Augusta, ME. I won't try to cram the photo here, but posted it on another board that is less restrictive on file size. I've shot groups that good with my better rifles, but this one was done in 30 degree weather and without spacing shots. Load was a Sierra 52 grain HPBT, 26.0 grains of Varget. I fired several groups without consideration of barrel temperature or cooling. Most were under 1/2".
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Old December 6, 2019, 11:18 AM   #7
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Never have figured out how one can shoot a .0077"(current, 5 shot, 100 yard, BR record.) diameter group with a .308" bullet
Group is center to center, so outside diameter of the hole at widest point, minus bullet diameter.
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Old December 6, 2019, 04:01 PM   #8
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A "one hole group", according to above definition, would measure 2x the dia of the bullet, outside to outside. A "one hole 308 win group would measure at max .616".
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Old December 6, 2019, 10:18 PM   #9
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I've shot one hole groups that really are less than caliber, because the consistency of the bullets going through the same hole created a minature blackhole.

Quote:
I was pleased to shoot what could be considered a "bullet-diameter" 3-shot group yesterday with my factory Rem 700 ADL, .223 in factory dress, Leupold 3-9X, but pillar-bedded/floated barrel, using unfired new Starline brass and Sierra bullets in 30 degree weather, off an old Hoppe's rest at our club range in Augusta, ME. I won't try to cram the photo here, but posted it on another board that is less restrictive on file size. I've shot groups that good with my better rifles, but this one was done in 30 degree weather and without spacing shots. Load was a Sierra 52 grain HPBT, 26.0 grains of Varget. I fired several groups without consideration of barrel temperature or cooling. Most were under 1/2".
I was shooting in Maine yesterday too--one of the rare days it hasn't been blowing 30 to 50 mph lately.
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Old December 7, 2019, 02:04 AM   #10
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Quote:
Originally Posted by reynolds357
A "one hole group", according to above definition, would measure 2x the dia of the bullet, outside to outside. A "one hole 308 win group would measure at max .616".
I think most folks refer to a "one hole" as exactly that, where all the shots are touching and you don't have any shots that are not separated. You can have a group that is one hole that is larger than 2X the diameter, it just depends how the shots line up.

Example:


That is technically "one hole", but not sub caliber. It is a .243, so ~.477" center to center, 8 rounds.

A sub caliber group would be what you describe, although to be truly "sub" a .308 Win would have to be .615"
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Old December 7, 2019, 02:05 AM   #11
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"If I do my part. . . ...

--------------------------------------------------------------------------------

A common reason for shooting a few shots into a sub caliber group. Sub caliber groups typically have extreme spreads less than bullet diameter; often called a "one hole" group.

What does that mean?
If it happens occasionally, it means that the shooter/rifle/ammo combo is pretty accurate. Even with random chance helping all the variables line up just right, resulting in the occasional group that's much smaller than average, the shooter/ammo/gun combo still need to cooperate to get all the shots into the right ballpark or there's virtually no chance at all of getting a subcaliber group.

If it happens on a regular basis, it means that the shooter/rifle/ammo combo is extremely accurate. Once it's happening regularly, it's more than just random chance.
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Old December 7, 2019, 12:03 PM   #12
Don Fischer
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I think this would be a one hole group. There's 5 shot's in one hole and I though four had just missed. Fired a sixth to see what was going on. Then walked down and ws right on the target before I could see the enlarged hole. 25-06 Rem 700 ADL, wood stock bedded and barrel floated, trigger set at 3#, 3-9x Bushnell banner, 100gr SMK. Only group I ever fired with that load, haven't shot the rifle since. Afraid I have never come close to doing this before and didn't really want my illusion popped! Rifle with 117gr Hornady IL normally goes just under 3/4". I measured outside to outside and subtracted one bullet dia. and came up with .111" group. As I said never came close to that before and doubt I ever will again.

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Old December 8, 2019, 10:28 AM   #13
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If I'd have shot that 5-shot group that was about the size of one bullet hole, I'd still be doing a "happy-dance". Then, I'd probably say, "There's no way I can do this again, so why keep trying?"

That's pretty much what I did after shooting two perfect Rimfire Benchrest targets and a third with the last shot that just made a 9 (of 10). Shortly after that, I quit the game, but was getting tired of running the program anyway.
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