Measuring accuracy or consistency

[MarkL]

Is anyone aware of any research, or at least conclusions, regarding different ways to measure bullet hole groups?

I know the convention is to shoot X number of Y shot groups, then measure the extreme spread of each group and calculate the average. However, I don't want to shoot more groups/shots than necessary, or waste my time by shooting fewer than necessary. For example, if I can be 90% confident that a 10% difference in group sizes is meaningfull by shooting three groups, I'd rather do that than shoot 10 groups to be 95% confident. Heck, I might settle for 80% confidence.

I'm looking for answers to questions like this

1) How many shots are enough and how many groups are enough to be X% confident that a given difference is meaningfull?

2) Is one 10 shot group better than two five shot groups?

3) If I measure the Average Group Radius (AGR) instead of the Extreme Spread (ES), can I reduce the number of shots required to get a statistically significant answer?

It seems likely that AGR is a better method than ES, but has anybody actually tested it? Just because everybody has been using ES forever doesn't mean it's the best method. One good reason to use ES is that it's far easier to do than AGR, but I have a computer program that makes AGR easy enough.

[Catfish]

Your asking your question to the wrong group of people. What you have here are a bunch of shooters and what you need is a statisation. Several years ago I read an artical somewhere that gave the porbibality of where you bullet would hit given your group size with a varying number of shots being fired for group size. I cannot remember where I see that now. I do remember that that 5 shot groups were a hole lot better that 3 shot groups and that 10 shot groups were even better. Now you have me thinking about it, I sure wich I could find that again.

[royinidaho]

Here's a way of doing it that I tried and be darned if it didn't seem to reduce the number of shots necessary to "zero" in on the correct amount of powder to use with a given bullet.

There's a name associated with this process but I don't recall what it is.

If this thread goes long enough someone will chime in with the good stuff.

Here goes.

Pick a bullet, primer and powder.

Start at "low book" and load one round at that powder weight. From there on load one (1) round with increasing powder weights of say 0.2 gr. NUMBER them consecutively from lowest weight up.

The go to the range. At least 200 yds is best.

Set up the chrono and shoot the round number 1. Record velocity and point of impact on a target (log) at the bench. Then shoot each consecutive round number recording its velocity and point of impact.

You will sprobably see some clusters of several consecutive round numbers. Maybe one cluster maybe more. Who knows.

Now you know where that combination of of primer, powder and bullet shoot the best and you have only expended 4 5-round groups worth of rounds.

If velocities are acceptable then you can start messing with primers, seating depth etc to squeeze things down a bit more.

I did it recently with a 223 and was impressed with the results.

If I would have used this process for the last 30 years I probably could have financed a pretty fair hunt with the savings. But..................

[Evan03]

alot of times number of groups or rds fired doesnt mean much to me.

depnds on what im doing. if im not shooting very well then ill fire just a few 3 shot groups through the rifle. but if things are workn out i get carried away and push 10 into a group. this i only do with my most acuarate guns.

other guns i site in work up a load and never see paper again. just get to varmit hunting. ive had very bad luck shooting paper at times and nothing but great results on live vermin.

[MarkL]

I believe the method royinidaho is describing is called

1) the Audette method
2) the ladder method
3) the Optimal Charge Weight method

A little googling will find detailed instructions on using it. However, it doesn't really do what I'm asking about, which is to compare two or more loads (or guns) to each other without having to shoot all day.

[Rocky Raab]

I'm not a statistician by any means, but I don't think I've ever been fooled by comparing five five-shot groups.

And it doesn't take laborious calculation of various deviations, deltas, variances or the like either. Just a plain old group size is all I need. I can average the five together, or just use a "gut-feel" middlin' number and be done with it.

As I've so often said, tiny groups are overrated unless you're a target competitor. Hunters can neither achieve nor benefit from benchrest-type accuracy.

[bulletpusher]

I agree completely with Rocky, a rifle that groups consistantly about 1 1/2" and less with the load that your using, and you can shoot it from what has become known as field shooting positions with somewhat close to that same consistant point of aim, then there is nothing else needed to make your hunt complete.

However, (like the perverable BUT!) I just love to go to the range and shoot those little tiny groups, that is when I'm doing my part, I do.

Those little tiny groups are extremly good for your mind, but all they are good for is braging factor. In the real world I can almost garante that the game that you hunt will never know if it was shot with a rifle that groups 5 " or 1/4" and if you can't do the same thing while hunting consistantly their worthless.

But do they feel so goooooddddd!!!

Bulletpusher

[Rocky Raab]

They do, indeed!

All of us have a "wallet group" tucked away somewhere as bragging material. And we deserve to!

[Cossack]

I'm interested in accuracy as it relates to how I use the piece. For shooting paper or varmints then multiple groups (at least 3) of X shots (5 in some guns with lighter barrel others ten) do the tick. I also consider if you have to clean the gun in the process, the consitancy of your hold, gun location on rest, etc. But for hunting, it's the first shot out of a cold barrel that matters most.

[skeet]

I had some reloaded shotshells tested at HP White labs...They wanted 5 rounds to get a 95% accuracy rate on velocity and pressure...20 rounds gave them a 97 1/2 % accuracy if I remember correctly... They told me 4 rounds they considered minimum to get an average of about 90%... Took a lot of money to have ammo tested then...like 20 bucks per shell. I wanted a real 75 yd goose load. Got one too. Looonnnggg way with a shotgun


Anyway that was the way they figured the statistics

[Cal Sibley]

If you're trying to determine your best hunting groups I think possibly you're putting far too much into it. The cartridge must be of sufficient speed and bullet weight to kill your animal cleanly. That's not hard to determine. Any reload manual will give you this data. Certain manuals will give you the best hunting loads, like Sierra. Go to the Remington site and see what the velocity and energy levels are for the various bullets, then modify it to suit your tastes and needs. Best wishes.

Cal - Montreal

[earschplitinloudenboomer]

I like Evan03's post, there are days that I know that I am wasting my time at the range. On those days I gain nothing for my research. I like to start low on powder charge, move up in one half grain increments, 3 shot groups 'til I'm close to where I need to be, fine tune the load to two tenths one way or the other for optimum performance...then shoot that load on different days. The consistancy of a good group, for me, means more than that one time exceptional group.

[MarkL]

Just FYI guys, this thread wasn't meant to be about hunting. Well, maybe varmint hunting, but not deer hunting. I am perfectly aware that 1.5 inches of accuracy is more than adequate for deer hunting. Most deer hunters never shoot or measure groups. My son dropped a deer this season with a .357 Magnum carbine that shoots about 4 MOA. I never had any doubt it was up to the task.

In short, I get it: The need for accuracy (and measuring it) depends on the application at hand.

The original question was basically academic. I was hoping for basically academic answers, rather than being told the question is moot or anal (which I admit it is in SOME circumstances). I enjoyed every response and agreed with most of them, but felt some were "off topic".

And just in case it isn't obvious, there are applications where 1.5 inches isn't so great. Varmint hunting and benchrest competition come to mind. I imagine there are other applications where 1/2 inch groups are meaningfully better than 3/4 inch groups. To some people, it is NOT a waste of time to look for better, more efficient ways to measure and compare accuracy.

[earschplitinloudenboomer]

Hey MarkL;
Thanx for the wake up call, I'm one of those that responded in general terms of "deer hunting" accuracy. I still feel however, that the group size is irrelevent if it's not consistant...blows heck out of your conficence too! Will try to pay closer attention to the quesion in the future.

[Rocky Raab]

Why, shucks, Mark, we's jist a-coverin' up fer not bein smart nuff to be akad...aced...acka...oh heck, book-larned.