I'd like to know what standards the top shooters are using when they say, "this lot of ammo produces XXmm groups in my rifle."
-How do they measure the group? I know that edge-to-edge measurement is typically used, but this doesn't answer all the questions. Do they measure the outside edges of the sooty print left by the bullets?
-How many shots are there typically in a group? 10 shots, 20, 40?
A lot of numbers are always being thrown around about group sizes but without standardizing on these parameters, comparison is impossible.
Standards in Measuring Ammo Performance
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bluetentacle
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metermatch
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Ammo testing
I don't think group size is measured by the outside of the bullet. It is usually measured CTC, bullet center to center. (or extreme spread)
As for the number of shots per group, honestly I think most people do it incorrectly - usually 5-10 shots pwer group, and shoot a number of those 5-10 shot groups.
If you want to convince yourself, take all of those 5-10 shot groups, and stack them on top of themselves, and see the group size. Now can you see the flyers???
I shoot 50 shot groups. Narrow it down to a few lots, and shoot the last rounds remaining in a 100 round pack of ammo to decide.
As for group size, I think a lot of what you hear will be exagerations. My standard was to be a group small enough to go 50 rounds clean on the International target. From there, every bit smaller is a bonus.
Remember, if the International target ten ring is 10mm in diameter, a perfectly centered 15mm group will go clean.
I'm sure there will be those that will produce 5 shot groups with all the bullets going through the same hole, claiming that is how accurate their gun is. Baloney. Go do that ten times in a row on the same target.
Jeff
As for the number of shots per group, honestly I think most people do it incorrectly - usually 5-10 shots pwer group, and shoot a number of those 5-10 shot groups.
If you want to convince yourself, take all of those 5-10 shot groups, and stack them on top of themselves, and see the group size. Now can you see the flyers???
I shoot 50 shot groups. Narrow it down to a few lots, and shoot the last rounds remaining in a 100 round pack of ammo to decide.
As for group size, I think a lot of what you hear will be exagerations. My standard was to be a group small enough to go 50 rounds clean on the International target. From there, every bit smaller is a bonus.
Remember, if the International target ten ring is 10mm in diameter, a perfectly centered 15mm group will go clean.
I'm sure there will be those that will produce 5 shot groups with all the bullets going through the same hole, claiming that is how accurate their gun is. Baloney. Go do that ten times in a row on the same target.
Jeff
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bluetentacle
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For whatever reason, international shooters/ammo makers do outside-outside group measurements. In general we also use 10-shot groups. I use many 10-shot groups to decide if a lot is worthy of trying it out of the shoulder. Eley uses composite 40-shot groups at their customer test range.
If all you are trying to do is get a lot that just cleans the international target, your group size is ~21.6mm...10.4mm ten ring + 2x 5.6mm bullet size (outside-outside). If I had a gun that had the best lot in that size range, the barrel is getting replaced. Heck, anything over 14mm is probably getting replaced.
Eric U
If all you are trying to do is get a lot that just cleans the international target, your group size is ~21.6mm...10.4mm ten ring + 2x 5.6mm bullet size (outside-outside). If I had a gun that had the best lot in that size range, the barrel is getting replaced. Heck, anything over 14mm is probably getting replaced.
Eric U
I guess it is easyest and quickest to measure extreme spread (edge tot edge) or covering circle. Al we want is a small as possible circular group with no flyers.
Eric, what do you consider decent grouping CTC or Extr spread? I know my 30 year old Walther GX-1 with original barrel occasionally shoots 14mm 5-shot groups at 50m (covering circle) from a rest with Lapua Pistol King.
Albert B
(The Netherlands)
Eric, what do you consider decent grouping CTC or Extr spread? I know my 30 year old Walther GX-1 with original barrel occasionally shoots 14mm 5-shot groups at 50m (covering circle) from a rest with Lapua Pistol King.
Albert B
(The Netherlands)
Yeah, 10-shot groups are a good indicator but not statistically significant to any sensible level of significance. They just sort of waggle their eyebrows suggestively whilst pointing and mouthing "Look over there".Eric U wrote:For whatever reason, international shooters/ammo makers do outside-outside group measurements. In general we also use 10-shot groups. I use many 10-shot groups to decide if a lot is worthy of trying it out of the shoulder. Eley uses composite 40-shot groups at their customer test range.
10-shot groups will identify good/bad but do not provide enough data to reliably rank the good groups from best to worst.
I believe at Eley they do 10 shot groups, eliminate the stuff that really properly doesn't agree with the barrel, do another 10-shot string, eliminate some more, and only end up doing the full 40 shots to separate the few best batches.
According to their website, the all-time range record is 13.9mm, so I'm guessing that's extreme outside edge not centre-to-centre (although it's over 40 shots, so you would expect a larger spread than a 10-shot group). They have electronic targets which feed the shot data into some custom software which composites the strings from each batch (because you won't shoot more than 10 shots of each batch at a time as it's a process of trial and elimination).
I always feel a twinge of pity for these guys who do "ammo reviews" and spend a lot of time, effort and money doing 5-10 shot groups with loads of different brands of ammo, because in the end they prove nothing on account of:
1. the groups are not big enough to be statistically significant;
2. even if they did 40/50 shot groups, then their results are only relevant to their barrel.
There are other problems with those sorts of tests as well, but those two factors alone mean those results are worthless.
Albert,
14mm isn't bad, considering the world's best .22's are only in the 12-13mm range, with occasional dips into smaller groups. The key is consistently. If your GX-1 never shot bigger than 14mm, then it would truly be a world beater. To me that is better than a gun/ammo combo that shoots 10mm most of the time, but has the once-in-a-brick 9.2.
One advantage to shooting 10 shot groups is that you can tell in ten shots (sometimes 5) whether a lot just isn't going to work in your gun. No point in shooting more if in 5 or 10 shots the group is bigger than the standard you have set for yourself. I would never shoot one good 10-shot group and declare that gun to be great. I had one gun that shot a 7mm 10-shot group. It never even came close to that again. For me it is a history thing...how does this rifle shoot over time. I'm talking weeks or months worth of testing and shooting out of the shoulder. If it passes the muster there, then I begin to think about shooting it in a match.
Eric U
14mm isn't bad, considering the world's best .22's are only in the 12-13mm range, with occasional dips into smaller groups. The key is consistently. If your GX-1 never shot bigger than 14mm, then it would truly be a world beater. To me that is better than a gun/ammo combo that shoots 10mm most of the time, but has the once-in-a-brick 9.2.
One advantage to shooting 10 shot groups is that you can tell in ten shots (sometimes 5) whether a lot just isn't going to work in your gun. No point in shooting more if in 5 or 10 shots the group is bigger than the standard you have set for yourself. I would never shoot one good 10-shot group and declare that gun to be great. I had one gun that shot a 7mm 10-shot group. It never even came close to that again. For me it is a history thing...how does this rifle shoot over time. I'm talking weeks or months worth of testing and shooting out of the shoulder. If it passes the muster there, then I begin to think about shooting it in a match.
Eric U
Absolutely. Eley count out batches after 10 shots as not worth carrying on with in that barrel, but would never recommend a batch after such a short shoot. 10 shots will give you a hint of what's going to work and what isn't, but it won't give you a ranking or strongly significant result.Eric U wrote: One advantage to shooting 10 shot groups is that you can tell in ten shots (sometimes 5) whether a lot just isn't going to work in your gun. No point in shooting more if in 5 or 10 shots the group is bigger than the standard you have set for yourself. I would never shoot one good 10-shot group and declare that gun to be great. I had one gun that shot a 7mm 10-shot group. It never even came close to that again. For me it is a history thing...how does this rifle shoot over time. I'm talking weeks or months worth of testing and shooting out of the shoulder. If it passes the muster there, then I begin to think about shooting it in a match.
Eric U
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bluetentacle
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Eric, do you use a scope when shooting from the shoulder, when testing ammo? I imagine that groups are invariably larger when shooting irons, even for top shooters.
Also, what do you align the fingers of the caliper against when measuring a group? Is it the sooty outlines of the bullet on the paper, or do you measure the centers of the furthest two shots and then add 5.6mm to the value?
Also, what do you align the fingers of the caliper against when measuring a group? Is it the sooty outlines of the bullet on the paper, or do you measure the centers of the furthest two shots and then add 5.6mm to the value?
I shoot out of a mechanical rest when originally sorting lots. I then move to a bench with a scope to narrow it down some more. Final test is in match configuration with irons in the prone position. From my limited scope shooting experience in American Prone, I shoot every bit as well with irons as I do with a scope.
I printed up a circle template on a piece of clear plastic that has circles in .5mm increments. I measure to the edge of the sooty mark on the paper.
Eric U
I printed up a circle template on a piece of clear plastic that has circles in .5mm increments. I measure to the edge of the sooty mark on the paper.
Eric U
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bluetentacle
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its a bit of a mix when it comes to ammo comparison
At the SISC (sydney International Shooting Centre obviously in Australia)
We can get our rifle set up on special benches, with a load of equipment that obviously measures trajectory and yadayadayada.
From that we select a few brands of ammo and do multiple test groups, mainly 5-10 shots. 5 is kind of your most common grouping size.
Thats one way to truly test performance is finding a centre that can get the right gear and so forth to measure everything accurately.
But mind you, it really does boil down to the shooter. A mate of mine definitely proved the worth of his rifle and ammo when one of his ISSF targets at 50m he shot all 5 shots on 10.8. Each round went perfectly through the same hole, and when measured it was no wider than that of a single shot.
In reference to what standards are used for how big groupings are, when just shooting on ISSF targets, we grab a clear pastic sheet which you place over a group and it shows you how big the group is, from the outside of the hole.
At the SISC (sydney International Shooting Centre obviously in Australia)
We can get our rifle set up on special benches, with a load of equipment that obviously measures trajectory and yadayadayada.
From that we select a few brands of ammo and do multiple test groups, mainly 5-10 shots. 5 is kind of your most common grouping size.
Thats one way to truly test performance is finding a centre that can get the right gear and so forth to measure everything accurately.
But mind you, it really does boil down to the shooter. A mate of mine definitely proved the worth of his rifle and ammo when one of his ISSF targets at 50m he shot all 5 shots on 10.8. Each round went perfectly through the same hole, and when measured it was no wider than that of a single shot.
In reference to what standards are used for how big groupings are, when just shooting on ISSF targets, we grab a clear pastic sheet which you place over a group and it shows you how big the group is, from the outside of the hole.