Realistic 10-shot groups

[Huntnful]

Having a realistic measure of your rifle's precision is useful in determining your max effective range. If you're holding 1.5 MOA off a bench at 100yd you probably shouldn't shoot a deer at 700yd in the field. 10 rounds isn't enough to really measure your rifle's precision, but it's a whole lot better than 3-5.

Exactly. And 10 shots to shoot a dependable zero as well.

 

[wild_musk]

In addition to the Hornady podcast, Shoot 2 Hunt has a several episodes that discuss this topic as far as group sizes, cone of dispersion, and sample sizes. I remember they point out 30 observations is a general minimum in statistics - thats just an example of one thing i remember, not advice on how to determine anything. I think they were talking with the guy from Gunwerks, some reps from Hornady, and another stand alone episode that goes into the realistic relevance of group size to long range hits on animals...fwiw. Sometimes it's easier for me to take in a podcast and think about the information. I tried finding the Litz podcast but I think you need a membership for them and I haven't decided on that yet.

 

[Philward]

After the first shot the group can only get larger.

 

[med358-boise]

Two comments:

1) it's all about the "use case" and "what am I trying to measure?"

2) consider the human error factor related trying to do 10 of anything in a row with extreme precision in a relatively short period of time.

I absolutely understand the value of larger sample size (just look at my sarcastic comment in my signature line) but consider what are you actually trying to measure? is it the accuracy of the load in the rifle or your ability to shoot 5 consecutive shots within a relatively short period with the exact same point of aim/hold.

Your 1/2 inch group went to 1 inch. So a 1/4 increase per side. At 100 yards, an increase in 1/4 inch means that your deflection in aim was .00000239 degrees off, if I remember my high school geometry correctly.

Unless the 5, 10, or 20 round group is being shot from a "ransom rest/vise" type of device; group size increase is likely more attributable to my inabilities or change in harmonics because of residual barrel heat or tiny change in wind velocity or direction. A change from 2 mph to 3 mph is ~.1 inches @ 100 yards.

 

[Culpeper]

Dispersion erodes any single group relied on. But it comes down to your range and target for the precision you need.

 

[HandgunHTR]

@Huntnful and @Hondo64d touched on it.

It isn't just about group size. It is about is Point of Impact the same as Point of Aim? i.e Is your rifle truly zeroed?

For those of you shooting 3 or 5 shot groups, are you comparing where those groups are hitting in relation to your point of aim? If you are and are constantly having to "adjust" your scope, then either your scope is not holding zero, or your actual cone of impact is larger than you think and you are just chasing your tail around by making constant adjustments.

That is what a larger group (20-30 ideally) tells you. It will give you the true center of your cone of impact. And allow you to set your zero correctly. Also, nobody is saying that you need to shoot these all in one sitting.

For those who still need a bit more explanation, if your 3 or 5-shot groups are all 1/2MOA, but the center of the cones are moving 1/2MOA, then in actually, you have up to a 1.5MOA system, you just don't know it. At 500 yards and in, it probably won't hurt you that much. But, stretch that out and add in some wind, and you go from a sure hit, to a miss or gut shot in hurry.

Increased practice never hurt anyone. Not sure why there is so much push-back to shooting more.

 

[R. Cram]

I shoot highpower and all our courses of fire are 20 shots at a max of 20 minutes so I don't ever play games with letting the barrel cool between shots, the rifle has to do what ever I want it to do. 3 shot groups are totally a waste of time unless you overlap 3 of the 3 shot groups, 5 shot groups may not be the bast but 10 times better than 3 shot groups, I just went to a match with my M1 garand and did not take my advice and in load developing shot a 5 shot group that was 2 1/2 inches at 200 for 5 shots and the result was what I wanted to see and due to laziness promptly loaded 500 rnds and found out that load was a lot more like 4 1/2 inches at 200. I have been fooled by 5 shot groups lots of times in the past, getting a good group and wanting it to be the answer so loading up a bunch to find out it really wasn't that good . for my highpower rifle I shoot the same cartridge, 260 and have many tens of thousands of rounds shot by lots of different barrels and if I load 42 gr of 4350 with a 140 I can go to a match at 600 yds and the load will more than likely be capable of staying in the 10 ring for 20 shots then If it doesn't seem to shoot enough x's I might fool around a little with it but I have learned after many ,many shots the guy pulling the trigger is the weak link so I firmly believe time is spent to a much greater advantage shooting and learning to read the wind than tinkering with reloading , unless you are a benchrest shooter then tinkering probably is important. I have shot at the 600 yd line a lot and reading the wind is 10 times more important than having a 1/2 moa for 10 shots rifle. when I put a new barrel on and shoot my normal load for the first time in that barrel if it is a switchy day or gusty day it is fairly hard to tell if that load is real good or not, if you want a long range load it should be shot at a long range.

 

[VinceMule]

The Wind has more effect on group size and identifying flyers caused by wind changes than most would ever imagine. Trying to talk guys into using wind flags is like a Doctor telling them to sit down to Pee.

Invest in two wind flags, put one up 15-25 yards from the muzzle, then another in front of the target you are shooting at. Get ready for a real education in how backward and ill-informed you have been for decades!

Effective wind flags are inexpensive to make out of 48", 1/4" rods available from the local hardware store, bicycle spoke, and 1/2" red yarn.

Concerning 10 shot groups, the barrel gets real hot in 3 shots, so the 4th and 5th shots are laying down some copper. Spacing your shots not to heat the barrel also increases the amount of time taken to shoot the group, allowing for more wind changes. The Wind pick ups and Let ups are a deal killer on groups. 10 shot groups are also a measure of how consistent the wind is for that particular time of day.

A wind flag is much more important than a 300-500 set of dies....trust me.

 

[Culpeper]

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[3800fps]

I do find this topic facinating. I have many years work experince with statistics and am amazed how I have never really put that knowledge ahead of dogma or tribal knowledge.

What I take from all this are a few things:

- averaging multiple 3-5 round groups is not the same as shooting larger groups, means almost nothing, worst it thinking the smallest I have seen is repeatable
- for hunting who cares what "MOA" your gun is, too easy to spend lots of time and money searching for better. If you have a bullet and velocity to do the job and groups at max distance that acheive what you need then be happy
- I'll no longer spend so much time on so many reload combination experiments, powder ladders, OAL ladders
- But if I want to understand what accuracy to expect when I train or compete, then I need to look at large groups so I know when problems are me, or when problems aren't.

I'll leave it there but facinating how many years I went thinking I knew things that now don't appear true. BUT still have a hard time merging the large sample size view with how there are very accomplished competition shooters who still use small groups to tell them which "load" shoots best.

JB

I've found that wide ranging experimentation with many powders, bullets, primers etc. isn't necessary.
With a given cartridge a proven good load is good in multiple if not most rifles in that chambering…seating depth tweaks, half grain of powder usually can dial it in.

Nosler reloading manuals over the years noted " most accurate powder tested" and "most accurate load tested"….over multiple cartridges their notations proved correct with those minor tweaks I mentioned and in multiple barrels/guns.

My greatest accuracy gains were achieved with meticulous brass sorting, trimming, annealing and otherwise uniforming techniques coupled with precision bullet seating tools and techniques.

Ambient temperatures, I've learned can wreak havoc on your best efforts…someone else must have thought so too cuz they decided to create "temperature insensitive" powders…
Better stock designs,better case designs, better powders, better CNC machining and near perfect bullet making techniques brought us light years forward in achievable accuracy.

 

[Mike6158]

Invest in two wind flags, put one up 15-25 yards from the muzzle, then another in front of the target you are shooting at. Get ready for a real education in how backward and ill-informed you have been for decades!

I bought NRA wind flags for the short range (300 max) that I shoot my tests at. They bought the flag poles. When I got there yesterday he was putting the new wind flags up AND they had a US and TX flag on a new flag pole. Lights are coming for the US and state flag. The firing line is covered and sometimes I put a Kestral, with base that lets in turn into the wind, on the bench next to me. It depends on what the wind is doing.

The wind flags are at 100 and 200. They showed me what I already suspected, the winds are weird at that range. There are trees, berms, openings and it's all surrounded by prairie and farmland. The 200 yard flag indicated wind from the east at 7, 100 indicated no wind. Then they both had an east wind. At one point one had west and one had east wind. Nothing too high yesterday though.

 

[quandary]

The increase in group size with an increasing number of rounds is normal. Five shots is actually a very small sample size and if you truly want to have a very firm idea of where your rifle is going to place the next bullet, it takes a 20-30 round group to do it. FWIW, MOA 10-shot groups from a lightweight hunting rifle is very good.

Many years ago, I used 3-shot groups because conventional wisdom stated "I'll never take more than three shots at an animal." But, I noticed that when shooting another group with the same load, the point of impact might be slightly different, or maybe the group would open up, having two shots touching, and one a little out. Why? So, I started shooting multiple groups at the same POA and saw that the composite group showed me a much truer picture of what that rifle/load combo was truly capable of.

Providing the whole system is sound, a rifle will fire all of its bullets in a cone. With the 6PPC benchrest rigs, this cone will be very small, with others, bigger, but still a cone. The more rounds you fire, the bigger this cone will get until the sample size is big enough to represent a high level of confidence in statistical variation. What we, as hunters want, is to put enough rounds in a group to have a reasonable idea of where the next round is going. We're this not so, we wouldn't shoot groups at all, but just a single shot. In order to preserve barrel life, I do this by firing three, or maybe five, let the barrel cool, then fire three or five more at the same POA until I have a composite group of the sample size I want. The more shots in the group, the higher your confidence level can be. Most of the time now, I use a 10-shot composite. While not absolute, it provides a much higher level of confidence than the typical 3 or 5-shot group. 20 shots is better.

For those that say 3 is enough, I challenge you to do as I did years ago, and stack a couple of more groups on top of the first one, letting the barrel cool between groups, and see how big the composite is. It will absolutely be bigger than the single group and it is very likely that your "1/2 MOA all day" rifle really isn't.

A larger sample size doesn't just apply to group size either. The same principle applies to zeroing and load development. If you shoot enough rounds, you will discover that your .3gr increase in powder charge doesn't make nearly the difference you thought it did. I wanted to find max for a particular rifle once, so loaded 10 rounds, increasing by .4gr per round, figuring the first time I saw excessive pressure signs, I'd back off .5gr and call that max. The composite 10 round group with 10 different charges went into one ragged hole, well under MOA. I could have picked any one of those powder charges and expected similar results.

Actually, group size is no longer my preferred indicator of how well my rifle is shooting. Extreme spread only takes into account the data provided by two rounds, the two that make the widest spread. Average distance from center is better and you really don't have to measure it, you can see it. If during load development, I have a charge where the extreme spread of two different charges is similar but one of them has 8 of the ten wadded into a tiny little hole and the other is randomly scattered, I'm going to pick the first.

John

First, John is absolutely correct. Second, is it just me or does anyone else find it ironic that this is exactly what Hornady said in the "Your Groups Are Too Small" podcast and no one is jumping on John. Maybe as a group we are learning.

 

[416pgw]

You only need to worry about your first shot on a cold barrel. If your first shot goes in the same place everytime with a cold barrel, your good. If you want to burn ammo for ten shot groups. Hell yeah I'm all about burning ammo. That's the fun of having a firearm. Real world your first shot is the most important shot for hunting

 

[VinceMule]

Mike, some rifle ranges are extremely difficult to shoot, especially if the predominant wind is a headwind which means that the range is facing the wrong direction. A headwind gives radical dispersion of flyers as the wind picks up and lets up.

I put out a wind flag around 15' from my bench just off the left of the line of sight. I shoot right-handed with both eyes open, and the flag at 15' is superimposed in the scope, while I look at the target with the second flag in the scope. This is not complicated at all, and you quickly pick up the wind pick-ups and let-ups throwing bullets out of the group.

IN plain English, your 3/4" gun may be a 3/8" gun, and you do not waste money chasing useless additional load development.

You have the confidence that the shots out of the group were wind, not load. Rock On!

ON a squirrely rifle range, you can pick up on the flags to watch, as berms, gaps in trees, or terrain create havoc with your groups. All you want to do is to identify flyers, and with confidence know why the flyer happened.

The wind flag trains you to be a better instinctive shooter, always aware that the conditions have a huge bearing on shot impact. We can not have wind flags in the field, but as hunters we pay attention leaves, grass, and wind on our face in relation to the direction, and speed, of the wind so we can put the bullet where we want it to go.