Evaluating precision of your rifle

[johara1]

Jeff is right if the first two don't cut move on, why waste barrel and components ..... jim

 

[dgeesaman]

I read this post and laughed, funny stuff. However my buddy who is a statistician convinced me I could get to the sweet spot of a barrel with 2 shot groups before shooting larger shot groups about 6 years ago. Been doing it ever since. Actually very simple, if the first 2 aren't tiny, extra shots won't shrink it.I hate consuming the barrel when it doesn't count.

I was thinking about that method yesterday. A wise statistician considers the cost of the data and the variance as shot count increases, and adjusts accordingly.

Now I realize you weren't using 2 shot groups this way, but it brings up a different possibility:
Let's say I have 50 shots to get a tune. Vary powder and seating depth only.

Traditionally, I might run 8x3 shot groups varying powder charge and 8x3 shot groups varying seating depth. Or 5x5 powder and 5x5 seating depth. Could I do better with 25x2 shot groups, varying both seating depth (5 depths) and powder charge (5 charges)?

2 shot groups cover all possibilities, albeit coarsely. The traditional approach doesn't even see most of the possibilities, but what it covers, it covers very well. It might be worth trying both on a barrel-friendly cartridge, or a barrel that doesn't matter.

 

[johara1]

I don't think two shot groups are great but why shoot more if the first two don't cut? unless you missed a condition change..... jim

 

[JEFFPPC]

I was thinking about that method yesterday. A wise statistician considers the cost of the data and the variance as shot count increases, and adjusts accordingly.

Now I realize you weren't using 2 shot groups this way, but it brings up a different possibility:
Let's say I have 50 shots to get a tune. Vary powder and seating depth only.

Traditionally, I might run 8x3 shot groups varying powder charge and 8x3 shot groups varying seating depth. Or 5x5 powder and 5x5 seating depth. Could I do better with 25x2 shot groups, varying both seating depth (5 depths) and powder charge (5 charges)?

2 shot groups cover all possibilities, albeit coarsely. The traditional approach doesn't even see most of the possibilities, but what it covers, it covers very well. It might be worth trying both on a barrel-friendly cartridge, or a barrel that doesn't matter.

I am not a statistician, but I took the advice of a friend, although I was very skeptical, and it works for me while saving me valuable barrel life. I just offer it as an option that might work for others.If you try it, let us know your results so we can all learn. When I speak of back to back groups in the zeros and ones, My final groups are usually 4 shots. I want to know when I go to the line the gun will deliver if I make the proper connection from gun to condition to trigger it gives me a good shot.If the shot is bad only question is, What did I do wrong.

 

[Dub]

You should buy a Teslong. It costs as much as a couple of tuning sessions.

I think the target is telling me what I need to know at this point. I think I will use the $$ for a new Barrel
Thanks for the suggestion

 

[KY_Windage]

Humm
Just to be clear on the technique your discounting all the shots except the best one and calling it 1/8 minute rifle !
Man I like your style...
J

I think there a lot of guys shooting one good group and then posting pictures of it for years.

 

[JEFFPPC]

fellas keep that same one in their wallet ta pop out like a flash card

A good shooter with good rifle does not save targets....he will shoot another good one next match.

 

[searcher]

After I narrow down my best two or three loads - I shoot three 5-shot groups of each in rotation so that each "run and gun" 5-shot group is shot is similar conditions to the group being compared. I then average the three groups of each load to compare with one another. I find this works best for me because the slightest shift in conditions might make you otherwise throw out what was the best load because it didn't show as well in one group. I think this works better than doing larger round-count groups because if, for example, one did 10-shot groups, you are going to want to allow the rifle to return to temperature before firing again - and you will have different conditions when firing the next group - and they can be dramatically different.

 

[JEFFPPC]

I was referencing your comment SPJ, on those whom carry targets around to show. I keep load developement targets and targets from breaking a range record. I have never kept other match targets. I will make a note on a given condition in my sight settings book at a given range if it fooled me. My focus at a match is beating the target. I never scan others targets when I finish mine, What they do does not help or hurt my score. Beat the target, you win or do very well.

 

[JEFFPPC]

Ah Yes’
I’ve misinterpreted your earlier post.
Probably old timers kicking in.

Interesting that comparing other targets from the same relay is something I have mixed feelings about, on one hand it helps me understand the conditions a bit so I don’t just think my loads goofy etc. on the other side I’m raised to mind my own business and compete against myself.
I appreciate your view, thx Jeff

Jim

Jim, I also have a case of old timers, maybe multiple cases some days. I never blame my loads ,I feel I have put that baby to bed before the match. So when I fall apart I feel I missed a condition or was guilty of poor gun handleing.Or, I lacked patience.

 

[INTJ]

A good shooter with good rifle does not save targets....he will shoot another good one next match.

But if I didn't keep my old match targets then I would have the fuss with finding the right size paper on tuning day before the match. It's much easier just to reuse the targets........

 

[Hohn]

I read this post and laughed, funny stuff. However my buddy who is a statistician convinced me I could get to the sweet spot of a barrel with 2 shot groups before shooting larger shot groups about 6 years ago. Been doing it ever since. Actually very simple, if the first 2 aren't tiny, extra shots won't shrink it.I hate consuming the barrel when it doesn't count.

For a rough screening, this actually makes a lot of sense.

I think it's helpful to flip our thinking about accuracy. To illustrate my point, I'll share a quote: "You don't train until you get it right, you train until you can't get it wrong."

What we really should be thinking isn't pursuing accuracy or evaluating precision-- but rather on driving out inaccuracy. Yes, it's kind of semantics, but it really is a different approach. A great rifle and a great load isn't one that can shoot good groups. It's one that seems to never shoot even mediocre ones. Ever. It's the one that on its worst day under awful conditions is still a 3/4" gun.

So if you are trying to identify the "stay away" areas in OAL or charge weight, two shots will suffice, because if a rifle and load combo is going to be a real shooter, the odds that you will happen to get the only two bad shots out of a thousand occurring right after each other, are VERY slim. If a combination is a true sweet spot, you'll never see it do badly, so you can eliminate those combos that show hints of it. (It's like when your date did something on the first date that helped you know early on this was NOT going to result in a follow up date).

You don't need a micrometer to tell a 3ft board from a 2ft board.

So with this logic, you start with coarse levels of development (paired shots, half a grain intervals, etc) and move progressively to more precise levels of refinement as you home in on a good combination. You will eventually (hopefully) get to the point where you will choose between two possible loads based on a 20rd score because 5 and 10 shot group won't distinguish between them.

The degree to which you can refine your confidence in a rifle and load is ultimately limited by barrel life and the rate at which is it consumed. A barrel burning load is difficult to refine to a very high degree of confidence because the it's literally never the same barrel twice-- each shot is eroding enough of the barrel to alter the boundary conditions of each succeeding shot.

 

[JEFFPPC]

But if I didn't keep my old match targets then I would have the fuss with finding the right size paper on tuning day before the match. It's much easier just to reuse the targets........

INTJ, I do the same with targets made of good matreial. I tape the holes then stamp the back side with a target stamp or I color binder ring reinforcments and put them on the back side of the old targets. The target I like to use for that allows me to put 4 rows of 20. That is more than required for the life of any barrel but I maintain it until the barrel is done then discard it.The notes for that barrel are written on the target . Anything I think is special goes into my note book for that cartridge. I have a note book for each cartridge.

 

[Falfan2017]

I like to shoot development groups on small pieces of paper so you can stack them up and see if the groups overlap.
For example you’re testing seating depths with 3 shot groups and you’re doing + .002 + .004 + .006 etc and they all go in the same group now you have a 9 shot group to look at it see how wide your tune is.

 

[JEFFPPC]

I like to shoot development groups on small pieces of paper so you can stack them up and see if the groups overlap.
For example you’re testing seating depths with 3 shot groups and you’re doing + .002 + .004 + .006 etc and they all go in the same group now you have a 9 shot group to look at it see how wide your tune is.

As your tune changes your point of aim changes, plus conditions. In my mind not sure about this, but the thought never occurred to me. Hmmm~m Anybody else do this?

 

[Falfan2017]

As your tune changes your point of aim changes, plus conditions. In my mind not sure about this, but the thought never occurred to me. Hmmm~m Anybody else do this?

I’m talking about all in one session within a few seconds of the last shots. Have a few pieces of paper with the bull all in the same place side by side and shoot em 3 shots on each with different seating depths or different powder charges. Then you can see if your 3 shot groups well but then overlap on to the other paper to see when you change the seating depth by 3k does that group go into the same hole or does it change position on the paper. It’s the same thing Cortina is talking about evaluating the position on the paper of similar loads but easier to see.

 

[Falfan2017]

As your tune changes your point of aim changes, plus conditions. In my mind not sure about this, but the thought never occurred to me. Hmmm~m Anybody else do this?

Here’s an example. Seating depth test one is .003 in the lands the next is .006 in. The .006 is the better group but when you overlap them you see that 2 rounds from the .003 group go perfectly into the .006 group with one round expanding it slightly. So this is probably a decent seating depth with a bit of room on each side. Haven’t had a chance to shoot this at 600y with everything being cancelled but it will be interesting to see if it holds up. The 1.812 is .003 in and the 1.815 is .006 in

 

[Burnt Powder]

The downfall of this method is that you are moving the POA/POI within your sample. A 5x5 is not nearly as instructive as a single 25-shot group all shot to the same POA.

When we speak of precision, we really mean what is our statistical confidence that our points of impact will fall within some distance from the point of aim. The military uses the Circular Error Probable idea as the circle that will contain 50% of the points. It's a circle that represents the median error from the point of aim.


As a shooter there are two ways to use the interrelation of confidence and group size. You can either fix the confidence first and then assess group size to that confidence level. Or you can fix a size reference first, then assess the confidence in those terms. But here's the key thing: WITHOUT BOTH DEFINED YOU CANNOT COMPARE.

The reason I took up midrange shooting was because I wanted real data on the actual precision of my rifle and loads. On an NRA target of known scoring rings, I can easily know this data. If I shoot a 200-14x on a sling face, I know with a 20 shot sample that 14/20 are ~sub-moa, so this is 80% confidence. A higher score might take me up to 88% or 92% confidence as X count rises. And in this case, it was 100% confidence of sub-two MOA. But that's only a sample size of 20 shots. Unless you are agg 600 with regularity, you don't have that 100% confidence in reality.

The more difficult method would be to calculate the size of the rings that would contain 90% or 95% or 50% of your shots, or whatever it is you want to use for reference. Either way is valid because it contains both the essential elements of confidence value and error value (group size).

I'm fairly certain that at one point or another, almost everyone on this board as fired a particularly satisfying bughole in the 2s or less. But, given enough shots and attempts, ANY RIFLE can and will do this. It just might take several thousand groups for one to do it or a single attempt for a very excellent rifle.

This is why group size is not only part of the picture, but it's probably the less important part. Without sample size and demonstrated confidence values, the group sizes themselves are next to meaningless. This is why those who point to a single five shot (or worse, three shot) group as demonstrating a rifle's capability are kidding themselves first, and us second.

That’s to anal for me! If I can consistently shoot 5 shot groups on multiple bullseyes as in Benchrest targets. They’re all the same as the first one, and can do it at will, every time I bag up, any day with a few different loads, then I know what I’m dealing with. I’m not a competitive shooter, unless you consider shooting prairie dogs with a couple friends where you get 10 shots or until you miss until the next guy shoots as competition? If I know my rifle shoots 1/2” groups with 5 shots today just like it the second Thursday last month and on New Year’s Day a year ago, it’s an accurate rifle that has a 100% confidence level for me! I know the rifle’s capability, if I miss, it’s not the gun!

Others have other requirements as you described, not most of us. Most people can’t shoot 2 5 shot groups in a row under an inch anyway. I’ve seen a lot of them try, rarely happens. I’ve got a few rifles that will do that, even if I’m not the operator, assuming the shooter is a shooter.

 

[JEFFPPC]

Thanks Falfan2017, sometimes my bulbs a little dim. It could be info with knowing if you load at a match.Knowing a load window with no impact notice would have value. Did you ever try it lat a longer distance and if so did the groups still overlap?

 

[Falfan2017]

Thanks Falfan2017, sometimes my bulbs a little dim. It could be info with knowing if you load at a match.Knowing a load window with no impact notice would have value. Did you ever try it lat a longer distance and if so did the groups still overlap?

I haven’t got a chance to try this one at long range yet. Just did this development at my local short range on Saturday. But in the past when loads made groups like that at short range it held up well at 600. Seems like vertical is the most important thing in short range load development. If you have even .1” of vertical at 100 it’s gonna be good for several inches of vertical at 600