Acceptable group size?

Chisqr

I’m always thrilled to see others who share my fascination of the statistical and probability sciences. The primary reason I only briefly mentioned its application in my original post is because on most forums….it is never well received.
I think this science “must” be used to quantify testing results and to make comparisons where the parameters of said test are changed to determine if “Change A” is better or worse than “Change B” to a statistician’s magical 95% confidence level.

About 9 months ago I started developing an Excel spreadsheet which I hoped would be “Plug and Play”. You would input the results for testing sessions comprised of ammo A vs Ammo B or a modification of the firearm or different tuner settings, etc, and Excel would then compute if a statistically valid change had occurred.

I had hoped one of the features of my program would be the ability to compare different size groups so if you had test data on say 3 shot groups or 5 shot groups, you could make a valid comparison against testing data on groups consisting of more than 3 or 5 shots.
It also makes for interesting observations in the different shooting disciplines which consist of more than the measuring of a 5 shot group. That being 25 shot groups for score used in many rimfire benchrest organizations and 40 to 80 shot group sizes for silhouette to name just a few.

To make a long story short, I reached the limit of my technical expertise in these matters and started corresponding with ballistic software authors and several University professors. I’ve been led to believe by several of them that solutions to my “Quest” are not as simple as I originally believed.

I would very much like to continue this discussion. Is it possible for you to PM me if you agree and provide your web site and/or Email?

Thanks, hope to hear from you and I also hope there may be a few others on this forum with an interest in this subject.
 
I took a ARA target I shot up in Wight City, MO, and measured 7 bullet holes on a target at random. They use a soft backer board similar to material on a clipboard but a lot thicker. This is softer material than what my range uses which is regular plywood. Anyway this is the measurement on the 7 bullet holes and the mean avg for each bullet hole. I could have done more, but this random sample should show the avg mean for each and every bullet shot on this target with this backer board.

.205
.205
.204
.205
.200
.194
.204
____

1.417 divided by 7 = .20242 for an avg mean for bullet diameter

Brad
 
Brad, explain how you get a .224 bullet through a .194 hole, then I will understand how a plug hurts on an ARA target. I know you say it prints a .194 hole but being an engineer, I find it hard to get a 1 inch dowel through a 3/4 inch hole.
 
The idea that a bullet will always punch a hole through paper that is exactly equal to bullet diameter is simply wrong. The hole size you end up with when you punch a hole thru any material is going to depend on the properties of the material. Everybody knows you can run a punch through rubber for example and end up with a zero size hole. Then if you punch through glass, what do you think the hole size will be? The properties of paper varies quite a bit and people use different types of paper (and backing) in their targets - thus the reason for different size holes. Unless the paper is very brittle or the bullet has a sharp wad cutter shoulder the hole is always going to be smaller than bullet diameter. The selection of .224 just works for most common papers, backing and bullets. However, most of the time when you run a .224 plug in you are enlarging the hole, which means you can't really measure overlapping shots with accuracy.
 
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MKnarr,

Maybe you can explain to me why a .224 bullet doesn't print a .224 hole on paper each and every time or at all for that matter.

I understand the reason for the .224 plug. You got to have a standard to go by even though the bullets that are shot on a target don't equate to a .224 size printed hole. I have measured several 22 bullet holes, and have yet to see one measure .224 on paper with my eyes doing the measuring. Like I said, I can see 20/13 with my glasses according to my optometrist who I recently just went and seen. I actually see better up close without them. He told me very few peoples eyes can actually focus well enough to see that well.

What would our English language be if when we printed a sentence on paper, and someone told you that is only print? You can't go by what was printed. It's inaccurate. ;)

I'm not saying a .224 plug shouldn't be used. What I'm saying is that how do you know that our bullets are in fact .224 in diameter when they are going through our targets. Explain that Mr engineer.

Brad
 
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If we can't go by what our bullets are truely printing for diameters on paper for score targets, then what makes the .224 plug the "Holy Grail" for our answer?

Brad
 
brad541thb said:
If we can't go by what our bullets are truely printing for diameters on paper for score targets, then what makes the .224 plug the "Holy Grail" for our answer?

Brad
Click to expand...

Brad,

.224 is the nominal diameter of the .22 rimfire. We all know different bores are not the same, nor are the bullets we shoot. Not to mention the targets and backers. You yourself noted the need for standardization. .224 is it. Answered your own question.

Ken
 
Ken,

Your correct. .224 is the standard.

So I guess it's just the way it is.

I was just proving a point that what a bullet actually prints on paper doesn't get scored by its actual print.

Brad
 
Brad, in this case, I can see no amount of logic is going to change your mind but what size hole does a wad cutter make. Cecil, we aren't talking about rubber.

From Steve Boleter's book, here are just a few bullet sizes: .225, .2237, .2241, .2251, .2235 and I could go on. As pointed out, nominal bullet diameter is .224. Now I will agree that the "appearance" of a bullet hole diameter in a "paper" is not the same as the diameter of the bullet. If one is going to measure group sizes by using only a dial caliper without any attachments then measuring one or more bullet hole diameters and using an average to calculate the group size I agree is correct. If one is measuring group sizes using a calipers with the appropriate attachment, then you don't need the bullet hole diameter and what diameter is the ring on the gauge.

Can we agree that the bullet diameter is not the exact diameter that the hole will be anyway but will be the bore diameter of the barrel. So we have a choice, build plugs for every diameter bullet, every diameter barrel bore or every diameter bullet hole that appears the paper. So you agree that the .224 plug is appropriate.

I have seen arguments all my shooting career that that bullet is in and that bullet is out using one size plug. Imagine if different size plugs were used. "Oh no, my diameter is smaller than that". "Oh wait, I shooting USBR so my bore diameter is larger than that." "Wait, I was using large diameter bullets today". "Look you used a .224 plug and that hurt my score." My point is, if the first three statements are incorrect, why isn't the third.

Pacecil, If I take a 1/2 inch diameter rod and put it through a piece of rubber, and don't pull it out, what diameter is the hole in the rubber? I'll bet it isn't zero.
 
Brad,

No arguement from me about the holes being smaller on paper. Common knowledge. Cecil is correct about the punch and rubber comparison, good example of what happens when the bullet passes thru the paper.

Ken
 
MKnarr said:
Brad, in this case, I can see no amount of logic is going to change your mind but what size hole does a wad cutter make. Cecil, we aren't talking about rubber.


Pacecil, If I take a 1/2 inch diameter rod and put it through a piece of rubber, and don't pull it out, what diameter is the hole in the rubber? I'll bet it isn't zero.
Click to expand...

MKnarr,

From you statement above, I assume your bullets are still in the holes when you measure your groups?

Ken
 
Maybe we ought to have both a printed score and a plug score method to score our targets. The guy that shoots the best printed score wins. :D

Brad
 
I'm going to give up, but one more time. Can we agree that the nominal bullet diameter is .224 before the bullet is fired. If not, stop reading and go on to something else because what I am about to say won't convince anyone anyway.

If the bullet major diameter is .224 and very close to that when it leaves the barrel and it goes through a rubber ARA target, how close is the edge of the bullet to any ring as it goes through the target. Remember the bullet hole has closed to almost zero and the smudge is just slightly beyond that. Does that mean we should decide what the score is for that bullet based on the existing hole size or should we base the score on where the outside diameter of the bullet was when it passed through the target. If it's the former, then using a .224 plug hurts in ARA and helps everyone else. If it's the latter, then a .224 plug neither helps or hurts anyone. And that is the crux of my argument.

My case is rested.

I apologize to all, I never wanted this to go this far.

Jim B.
 
MkNarr,

I have to go to the store right now and take my daughter somewhere. I'll give you a response when I get back.

I hear what your saying and like what Ken said that I admit there has to be a standard used.

Brad
 
Jim B..

You're not going to win, you are p---ing in a fan... As long as somebody types a reply, the argument will go on..

I believe as you do, but I refuse to get in an online argument with anyone on this subject..

Cheers..

Dave
 
I thought for years a 22 RF was .222 and 22 CF was .224, anyone know when the factorys changed the RF to .224 ?. and as long as everyone uses a 224 plug why should anyone care ?.
SS
 
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Jim,

Yes we can agree to the bullet being very close to .224 for most bullet used. Yes I see the reason for the .224 plug, but what I said still is true that our bullets aren't being scored by their true print on paper. I never meant for this to go this far either. The point is mute as Ken has said. I understand why we can't use the bullet hole print for it would be unfair to all to do so. But that still doesn't make what I said here not true. My point really was to get those to realize who seem to think they can deduct .224 for bullet diameter when our bullet aren't printing .224 holes on our groups that we are only shrinking our groups and our egos in doing so.

I'll stand by what I have said about bullets not printing a .224 hole even though there will be those that claim they do. I say get your eyes checked or send me your targets so I can prove you wrong with pictures and a caliper showing so.

Dave,

Nah never mind, I'll keep it in.

Brad
 
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A little information on scoring plugs & sizes,All of the plugs that i have made have a .190 stem & a .224 plug Dia. The .190 stem goes into the hole in the paper snug & centers the plug close to where the actual hole is,It is very difficult to place a exact spot as to where the bullet went through the paper because the bullet does not enter the paper straight,It is going in on a angle,& different rifles cause the bullets to yaw in different directions,Everyone knows that when you shoot a IR 50/50 target,you want your shots to be high,Rather than low because the bullet is going through the paper with its nose up & tail down,Your chances of getting protest in your favor is greater with a high shot than a low one.On the ARA target the same applies,shots that are high have a better chance of pluging a 100,because the bullet has its tail down,& when you shoot in a strong wind,the tail of the bullet will be pushed by the wind,because the bullet always turns it nose into the wind.The IBS is now going to the Glass Reticle scoring system,We Made & tested them 10 years ago & we found that there is to much scorer error useing the Glass,No 2 people can center the glass ring on a bullet hole the same,We tested 10 shooters & all 10 came up with different results,.The real problem lies in the paper,it does not show a true hole & if the bullet tears the paper it can be very difficult to tell where the exact center is,Let the paper get wet or damp & you really have a problem,I have seen 22 bullets make a 30 cal hole in a target when they were wet,We shot the IR 50/50 Nationals a few yers back in Richmond& it was a downpour,Milt Cook,who was the Director,Told the Referees not to even try & plug the protested targets,The holes were massive..224 is the standard size for official scoring plugs,This was adopted by the NRA & other disiplines when ever . BILL
 
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