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April 16, 2018, 11:40 PM | #76 | |||
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Similarly, someone firing 40 shots in a single group, or choosing to average three 10 shot groups should expect to find that the results of their arbitrary choices will not be representative of firing a 25 shot group or choosing to average five 5 shot groups. Of course, all of that is really neither here nor there. The point is that if you shoot a large number of shots into one group and make one mistake, it is the mistake that is going to dominate the results. If you fire more groups and average the results, a single mistake can only affect one group and the effect of averaging will reduce the impact of that mistake in the overall results. Quote:
If the point is to determine how you, your gun or the ammo perform in the worst case, then, of course, the most important statistic is the largest group. Quote:
On the other hand, if you put all your eggs in one basket and that result turns out to be atypical, you have spent a lot of work on a result that doesn't tell you much.
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April 17, 2018, 12:25 AM | #77 | |
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If you make a mistake that you aren't aware of, then how do you label a shot a mistake if you are not aware of it being a mistake? Logic says you can't. You have to include it because it might not be a mistake. It might be an accurate reflection of the gun/ammo. The only 'mistakes' that count are the ones you know are mistakes, and they should be excluded from the measurement. How many samples do you have to take? |
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April 17, 2018, 01:29 AM | #78 | |||
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I'm not really in favor of trying to pick and choose which shots to keep and which ones to leave out when shooting groups because... Quote:
There's also the situation where you know you made a mistake but you're not sure which shot on target it is. Maybe the "flier" that is high and right is the mistake you know you made, or maybe it's telling you about an ammo problem or a gun problem, and the actual mistake wasn't actually as bad as you thought it was. Once you start trying to pick and choose shots or groups, then you're never really sure if the numbers are telling you about how the shooting is going or if they're telling you how good you are at throwing away shots or groups to make the results come out the way you want them to. Quote:
Or, you could just pick a number of groups you want to shoot and pick the number of shots per group that seems reasonable to you and go for it. Five shot groups are pretty common for handgun accuracy evaluation and averaging a handful of those should provide decent results. You'll see that approach commonly used in published reviews. I've seen much larger group shot counts used for accuracy evaluation, but only with machine rests, or when some similar technique is used to take the shooter out of the equation as much as possible.
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April 17, 2018, 12:18 PM | #79 |
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I shoot handgun groups to test ammo and the gun and they are always 5-shot. Using a mechanical rest you still have to change magazines and I always check the torque on the rest when I change mags. If you move the gun in the rest changing mags and/or change torque on the screws it will change the impact point from previous groups which has nothing to do with the performance of the ammo-firearm combination. If the gun shoots a 2" group @ 50 yards and then after the magazine change it shoots a 2.25" group but the group center moved an inch left, the inch move had nothing to do the firearm or ammo but moved because of disturbing the rest. In testing you have to do your best to remove all of the outside variables and get to just the gun and ammo. If I shot 50-shot groups you will be wasting ammo more than getting information. Now if you are testing the rest, your procedures will change to reflect that. YMMV
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April 17, 2018, 07:22 PM | #80 | |
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April 17, 2018, 08:37 PM | #81 | |||
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If one is trying to evaluate their worst case performance, they should shoot blindfolded. That would fit the description. Quote:
There is variability even with multiple groups shot from a Ransom Rest, so stability in group size is a bit of a myth. In this article (https://americanhandgunner.com/exclu...city-accuracy/) the author found up to a nearly three-fold difference in group size when shooting 15-shot groups (many more rounds than mere 5-shot groups) from a Ransom Rest. Quote:
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April 18, 2018, 12:22 AM | #82 | ||||
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If there's any doubt at all about which shot is the flier, or whether or not the shot really was a flier, then throwing it out might make the shooter feel better and the group smaller, but now there's something other than the shooter's ability, the gun and the ammo contributing to the results. Just throwing it out without shooting another shot doesn't sense as now the group being evaluated is a smaller number of shots than originally intended which means it isn't comparable to the other groups shot. And, of course, if the shooter's ability is a big part of what is being tested, then throwing away "fliers" doesn't ever make sense because fliers are clearly saying something about the shooter's ability. Quote:
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But a shooter whose groups vary by a factor of 2 or 3 clearly isn't shooting stable groups. Could be an ammo problem, a gun problem, a shooter problem or a combination. By the way, using a machine rest doesn't guarantee accuracy or consistency--it only eliminates shooter error. If the ammo or gun is the problem then there's nothing a machine rest can do to fix the problem. The article is interesting--the author's main point is that even with very consistent ammunition velocities (and a machine rest), it is still possible to get inconsistent results. That doesn't mean he's saying that stable groups are always impossible, he's just showing that one can't assume that consistent velocities = consistent accuracy. Quote:
I do agree that for some kinds of testing (particularly from a bench or using a machine rest) larger group sizes can make a lot of sense.
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April 18, 2018, 12:54 AM | #83 |
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My goodness, JohnKSa, we might be in near total agreement!
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April 18, 2018, 12:56 AM | #84 |
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Obviously there's something wrong! Let me re-read my post and try again.
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April 18, 2018, 11:28 AM | #85 |
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for my purposes (and to borrow a southern phrase)...
"fellahs, ah think y'all are overthinking this a bit...."
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April 18, 2018, 11:52 PM | #86 |
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Interesting article in the May 2017 issue of SWAT magazine. The author tested a 9mm carbine with various ammo, shooting from the bench.
Average 5 shot group sizes at 50 yards were: Atlanta Arms 115gr JHP--1.55" Black Hills 115gr +P JHP--1.25" Winchester 115gr FMJ--1.88" These groups, scaled to 25 yards would be 0.78", 0.63", and 0.94".
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April 19, 2018, 08:50 AM | #87 |
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I did this test about 10 years ago, with a P210-6 at a 50ft range. Premium 147gr hollowpoints tended to do the best (speer gold dot and whatever winchester was calling theirs at the time) -- I was able to get some 5-shot groups that could be covered with a quarter. I also recall that the 124gr gold dot load was very close to the same, so I ended up using that as a self-defense load. Bulk WWB 115gr practice ammo tended to do much worse, to the extent that groups looked about the same as those coming out of a Glock 19.
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April 23, 2018, 10:29 AM | #88 | |
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If a gun is improperly aimed (or the sights are off) when clamped to a Ransom Rest, the accuracy may be off, but the precision should still be good. If the is not properly clamped or the rig is allowed to move, more variation will occur (less precision). Basically, I am arguing that a gun that is properly mounted in a Ransom Rest that is properly secured, should yield the maximum degree of precision allowed by the combination of the gun and the ammunition.
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April 23, 2018, 10:46 PM | #89 | |
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April 23, 2018, 11:44 PM | #90 | ||
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So 'accuracy' isn't about "hitting the target" as much as it is about whether or not the group is centered on the target. A gun that spreads impacts into a group size of 3 feet at 10 yards is still perfectly accurate as long as the group is perfectly centered on the point of aim. Using the technical definitions, any non-defective firearm with properly functioning adjustable sights can be made to be perfectly accurate by properly adjusting the sights. Barring fixed sighted guns or guns which need repairs, all guns are only a sight adjustment away from being perfectly accurate by the technical definition. But all that is really neither here nor there as the technical definitions of those terms are not the accepted definitions in the field of firearms. When people talk about firearm accuracy, they mean how small the groups are. When they talk about guns that don't center their groups on the target, they're not talking about inaccurate guns--they're just talking about guns that need their sights adjusted. Perhaps, with a major concerted effort and a lot of time, it might be possible to win the firearm community over to using the technical definitions, but it seems to me that there are much better ways that level of effort could be expended. Quote:
If I take the best machine rest ever made, clamp a .40S&W pistol into it, perfectly following all the instructions for the rest, and load the pistol with 9mm ammo, then even the " maximum degree of precision allowed by the combination of the gun and the ammunition" is still going to be miserably inaccurate, imprecise, or whatever one chooses to call it. The rest can eliminate shooter error. It can't do anything to fix problems with the gun/ammo combination. In other words, using a machine rest doesn't guarantee accuracy or consistency, it only eliminates shooter error.
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April 24, 2018, 06:31 AM | #91 |
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How is this?
I shot these groups @ 7 yards with my Kimber Micro 9.
Checking out hand loads with the Chrony. Center 10 shot group was 115 powder coated Lead@ 1182 fps Bottom Right 10 shot was 124 FMJ @ 1127 Fps Bottom left was 5 shots of 147 Gold Dot 919 Fps. Blew my mind. Accuracy! Same day, same gun...... David Sight was held where the red line is @ 6 o'clock. Gun is supposed to his where the dot on the front site is. I would have to cover the black with the sight, not good for analyzing groups. I am basically a bullseye shooter. This is the best group out of this gun in its first 1,000 rounds. 3.1" barrel. |
April 24, 2018, 12:11 PM | #92 | |
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Someone shooting the same combination of gun and ammo should not be able to produce tighter groups than a properly mounted gun on a Ransom Rest. So given your example, the grouping of the .40 S&W firing from a Ransom Rest should still be tighter than a shooter shooting hand held. This is of course given a large enough sample size to eliminate flukes. https://en.wikipedia.org/wiki/Accuracy_and_precision
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