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Offhand Breech vs Fixed (Read 17544 times)

wcf3840 Senior Forum Member Offline ASSRA Life #299 Posts: 355 Location: Palatine Joined: May 28^th, 2007	Re: Offhand Breech vs Fixed Reply #45 - Mar 12^th, 2014 at 4:04pm	Print Post
	When I was 19 and shooting on the rifle team, a Gunny told me, "Son, you're a pretty good shot. Now you need to get up to your ass in brass." I've been experimenting with fixed for offhand because it gives me less to think about on the line. The less my mind is working, the better I shoot. All this statistical stuff makes me dizzy.


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westerner Frequent Elocutionist Offline deleted posts and threads record holder. Posts: 11474 Location: Why, out West of course Joined: May 29^th, 2006	Re: Offhand Breech vs Fixed Reply #46 - Mar 12^th, 2014 at 4:36pm	Print Post
	Don't let it bother you. It's all a bunch of neurotic BS brought about by winter weather, cabin fever and lack of fresh air to the brain. It happens. Joe.

	A blind squirrel runs into a tree every once in a while.
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frnkeore Frequent Elocutionist Offline Posts: 7282 Location: Central Point, OR 97502 Joined: Jun 16^th, 2010	Re: Offhand Breech vs Fixed Reply #47 - Mar 12^th, 2014 at 5:14pm	Print Post
	wcf3840 wrote on Mar 12^th, 2014 at 4:04pm: When I was 19 and shooting on the rifle team, a Gunny told me, "Son, you're a pretty good shot. Now you need to get up to your ass in brass." I've been experimenting with fixed for offhand because it gives me less to think about on the line. The less my mind is working, the better I shoot. All this statistical stuff makes me dizzy. For me, BSing gives me a break between shots, especially bad shots Frank

	ASSRA Member #696, ISSA Member #339
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joeb33050 Frequent Elocutionist Offline Posts: 2613 Location: Marathon, FL Joined: Apr 20^th, 2004	Re: Offhand Breech vs Fixed Reply #48 - Mar 15^th, 2014 at 3:51pm	Print Post
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	« Last Edit: Mar 19^th, 2014 at 6:16am by joeb33050 »

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joeb33050 Frequent Elocutionist Offline Posts: 2613 Location: Marathon, FL Joined: Apr 20^th, 2004	Re: Offhand Breech vs Fixed Reply #49 - Mar 15^th, 2014 at 3:52pm	Print Post
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	« Last Edit: Mar 19^th, 2014 at 6:15am by joeb33050 »

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westerner Frequent Elocutionist Offline deleted posts and threads record holder. Posts: 11474 Location: Why, out West of course Joined: May 29^th, 2006	Re: Offhand Breech vs Fixed Reply #50 - Mar 15^th, 2014 at 4:58pm	Print Post
	[/quote] Look at Joe's target above ... the low and high shots - called or not - are due to an assignable cause. That blows the Gaussian distribution quotient out of the water, as it only works on normal distributions. I personally don't believe statistical predictions can be made with the groups most people shoot. We have found the problem folks - and it be within us! Like others have said, a good offhand group and/or score is more predicate on the performance of the shooter than the basic inherent capabilities of the said equipment. Eliminate the errant shots by continuously working on your technique ... and your scores and groups will improve! [/quote] Joe.

	A blind squirrel runs into a tree every once in a while.
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joeb33050 Frequent Elocutionist Offline Posts: 2613 Location: Marathon, FL Joined: Apr 20^th, 2004	Re: Offhand Breech vs Fixed Reply #51 - Mar 19^th, 2014 at 6:11am	Print Post
	rgchristensen wrote on Mar 11^th, 2014 at 10:11am: joeb: Mean radius, radial SD, and group size can be inferred from one another ONLY if you know the distribution. I don't think so. Given that one can prove a Gaussian distribution (not easy, nor safe to assume), you can readily relate these quantities. For other distributions, the math can get hairy. Interesting parallels are found in the evaluation of shotgun patterns. CHRIS RGChristensen ARE GROUPS DISTRIBUTED NORMAL? Much of what follows is based on the assumption that group sizes, or at least average group size, is distributed normal. This paper is in support of that assumption. How are "normal" groups and group sizes modeled? In "A GROUP SIZE MODEL" the horizontal and vertical deviations of each shot are distributed random normal and are the same for horizontal and vertical (means round groups) with average (= arithmetic mean here) of zero (means groups center is at zero). Another try. Each shot location is at H(orizontal) and V(ertical) where H and V are distributed random normal with average = 0 and standard deviation s. The model shot deviation is distributed normal. Shot location is H,V; first shot at H1V1, second shot at H2V2, third shot at H3V3…nth shot at HnVn. The distance between H1V1 and H2V2 is sqrt ((H1-H2)^2 +(V1-V2)^2). We'll call this distance D1,2. Then group size is the maximum of the combinations of D1,n, (composed of D1,2; D1,3; D1,…D1,n; D2,3; D2,4;D2,…D2,n; all the way to Dn-1,n.. (C of n, r at a time = n!/r!(n-r)!) Another try. The group size of a 5 shot group is the maximum of the distances 1,2; 1,3; 1,4; 1,5; 2,3; 2,4; 2,5; 3,4; 3,5; 4,5. Thus the model produces group sizes with any standard deviation and mean, commonly with H and V standard deviations equal and means = 0. Other values may be used.


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joeb33050 Frequent Elocutionist Offline Posts: 2613 Location: Marathon, FL Joined: Apr 20^th, 2004	Re: Offhand Breech vs Fixed Reply #52 - Mar 19^th, 2014 at 6:11am	Print Post
	Are the model group sizes distributed normal? With H and V equal and means zero, yes. (Maybe under (m)any H and V conditions.) Are model group size averages distributed normal? Yes, the Central Limit Theorem tells us that as n increases, x bar approaches mu and s approaches sigma. Are real group sizes distributed normal? Start with another question. Are real H and V distributed normal? I don't know. Are real group sizes distributed normal? H and V may or may not be distributed normal. However, as n increases, the distributions of H and V approach normal; and real group size distributions approach normal. Are averages of real group sizes distributed normal? If we average sets of n group sizes, the distribution of averages approaches normal as n increases. If a purpose of shooting groups is to learn about effects of variables on accuracy, we must compare averages of group sizes, and if averages differ slightly then a lot of groups must be averaged. I think that in this context it is not improper to suggest that group size averages are or approach being distributed normal as n increases. We have some evidence that real group sizes may be distributed normal. CAST BULLETS FOR BEGINNER AND EXPERT, Third edition, appendix, "7 Sigma as a Fraction of x bar". CBA 2002 and 2004 NM and other data, combined, showed that the ratio of standard deviation/average group size for 5 shot groups was .275 and for 10 shot groups was .179. 5 shot Jeroen Hogema of The Netherlands performed a 6,600,000 shot Monte Carlo simulation using the group size model and got .2691 and .1947. (My Monte Carlo simulations since have produced about the same numbers, however I'm limited to sets of 60,000 sets of shots.) The distribution or real group sizes and of normal distribution group sizes have about the same values of standard deviation/average, suggesting that the group distributions are similar if not equal.


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joeb33050 Frequent Elocutionist Offline Posts: 2613 Location: Marathon, FL Joined: Apr 20^th, 2004	Re: Offhand Breech vs Fixed Reply #53 - Mar 19^th, 2014 at 6:12am	Print Post
	As another check, I went back to the central Limit Theorem. Since s = sigma/sqrt n, and if s is .2691,(Hogema), then sigma = s * sqrt n = .269 * sqrt 5 = ~.602. The population standard deviation is .602 * mean. If we use the 10 shot estimate of s, .1947, then sigma = .1947 * sqrt 10 = .616. These are close enough for me to believe that the model distribution ia operating as normal, the real data looks like the model data, and and the real group distribution approaches normal. The underlying assumption supporting X bar and r charts is that no matter the shape of the distribution of the measured variable, the averages of n measurements is distributed normal with x bar = mu and s = sigma/sqrt n. If the assumption works in the Statistical Process Control world, I think it works in the shooting world.

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joeb33050 Frequent Elocutionist Offline Posts: 2613 Location: Marathon, FL Joined: Apr 20^th, 2004	Re: Offhand Breech vs Fixed Reply #54 - Mar 19^th, 2014 at 6:23am	Print Post
	Lefty38-55 wrote on Mar 11^th, 2014 at 10:18am: Look at Joe's target above ... the low and high shots - called or not - are due to an assignable cause. I don't know that. See the attached about outliers and flyers. We must at least note the probability that a shot is a flyer, and we can't do that without measuring and doing some arithmetic.. That blows the Gaussian distribution quotient out of the water, as it only works on normal distributions. I personally don't believe statistical predictions can be made with the groups most people shoot. We have found the problem folks - and it be within us! Like others have said, a good offhand group and/or score is more predicate on the performance of the shooter than the basic inherent capabilities of the said equipment. Eliminate the errant shots by continuously working on your technique ... and your scores and groups will improve!


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joeb33050 Frequent Elocutionist Offline Posts: 2613 Location: Marathon, FL Joined: Apr 20^th, 2004	Re: Offhand Breech vs Fixed Reply #55 - Mar 19^th, 2014 at 6:34am	Print Post
	Lefty38-55 wrote on Mar 11^th, 2014 at 10:18am: Look at Joe's target above ... the low and high shots - called or not - are due to an assignable cause. That blows the Gaussian distribution quotient out of the water, as it only works on normal distributions. I don't understand the sentence above. Please explain. What "only works on normal distributions" I personally don't believe statistical predictions can be made with the groups most people shoot. We have found the problem folks - and it be within us! We certainly can't predict individual scores or group sizes. However, we can predict many values, and we can understand the relative importance of error classes. Ain't that nifty? Like others have said, a good offhand group and/or score is more predicate on the performance of the shooter than the basic inherent capabilities of the said equipment. Yes, I kinda proved that using the dreaded statistics. Eliminate the errant shots by continuously working on your technique ... and your scores and groups will improve! Not true, unfortunately. I'm living proof. Neither you nor I will shoot like Jim Feren, no matter the practice. Talent beats practice every time.


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QuestionableMaynard8130 Frequent Elocutionist Offline Posts: 4144 Location: Benton Harbor MI Joined: Apr 17^th, 2004	Re: Offhand Breech vs Fixed Reply #56 - Mar 19^th, 2014 at 9:41am	Print Post
	But, well-practiced talent, beats raw talent every time

	sacred cows make the best burger
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