# of Shots per Group and MOA - Results

[ndking1126]

• Basically, it looks like if you want to shoot small numbers of shots per group, then you'll want to shoot several groups and take the largest group size to be your rifle/shooter accuracy.

Great post and great work. This comment above is always a question I've wondered, but no one seems to do any analytics on. Everyone says "shoot 5 shots or more" (understandably), but I've always thought if I can shoot 4 3-shot groups that all hover around .75", isn't it safe to say the multiple 3 shot groups provides data that is just as valid as 1 5 shot group? Of course I agree with your point that if you had one 3-shot group that jumped to 1", you can't just throw that out, you'd have to consider that the true accuracy potential.

I did want to ask though, 17 shots gives real possibility of human error.. 4 or 5 shots we can usually string together without much issue, but getting 17 in a row right takes skill. How do you feel you shot? Do you think you pulled any of the shots? What was your rest?

 

[jrock]

Nice write up. I use 3 shot groups in my load development. By time I'm satisfied with a load, I end up having 4 or 5 sample groups which were shot on different days and conditions. I overlay them to compare a few parameters and they end up (or should end up) being very similar. I also like to read the hit probability articles over the PRS blog.

 

[speedengineer]

Great post and great work. This comment above is always a question I've wondered, but no one seems to do any analytics on. Everyone says "shoot 5 shots or more" (understandably), but I've always thought if I can shoot 4 3-shot groups that all hover around .75", isn't it safe to say the multiple 3 shot groups provides data that is just as valid as 1 5 shot group? Of course I agree with your point that if you had one 3-shot group that jumped to 1", you can't just throw that out, you'd have to consider that the true accuracy potential.

I did want to ask though, 17 shots gives real possibility of human error.. 4 or 5 shots we can usually string together without much issue, but getting 17 in a row right takes skill. How do you feel you shot? Do you think you pulled any of the shots? What was your rest?

Thanks! You're definitely right about the human error side of things. I suppose one has to decide whether or not they want to include those pulled shots in the groups. For me, it would depend on the reason for shooting the group - if it's for load development, I wouldn't feel too bad about removing them. But if I'm trying to ascertain my capability to hit a target/animal at range, then I would include my errors since they could happen in the field too.

I actually did have 3 shots that I called as "pulled" prior to looking where they hit. I removed them from the analysis. My local range has removed all the sand bags used for rifle rests due to Covid, so I am blaming my pulled shots on having to shoot off of a chunk of wood.

 

[LRNut]

Excellent work; I get so tired of hearing folks say "Three shot groups are good enough because I never shoot more than three at an animal."

This just demonstrates a complete lack of understanding of statistics and probability. I founded a data analytics software company; in sales presentations I would sometimes ask how many pitchers have pitched perfect games in the big league modern era. The answer is 21. I then ask how many have done it more than once. The answer: zero. So cherry picking the absolute best performance and trying to understand how you got there is generally futile. Better to pick something you have demonstrated is possible, even if difficult.

 

[J E Custom]

There are many reasons for the group size to increase the more shots you take.

The main thing I have found it barrel condition changes over the full series of shots. if you start with a clean barrel and do your best to control the temperature and your fatigue. you will find that at some point the accuracy/group size will open up due to fouling. Most custom quality barrels are effected starting at 4 to 7 or 8 shots. even though not a practical hunting scenario I like to first find out how many shots a rifle can do before accuracy starts to degrade by cleaning and shooting evenly spaced (Time) shots. Then I will clean again and shoot that number again. two or three groups under these conditions will tell me just how accurate the rifle is.

For hunting this makes more sense than just shooting 20 shots in a row when one or two shots are the norm. For match shooting where 20 shot strings are the norm, it is good to find out where the barrel fouling settles down and is consistent. some rifle barrels take 8 to 10 rounds and others may take many more.

For load work up I like and recommend cleaning before every load change to make the test apples to apples. If you need to fire a fouling shot before starting the test, do so. (Many barrel will throw the first shot and settle in for the next 4 or 5. I have some hunting rifles that this is the preferred process and others that shoot the first round in the same spot as the next 4 or more.

If you want to shoot 20 shots to get maxim group size that's fine, but there are a lot of variables that can skew the end results, so I would recommend shooting 4 five shot groups on different targets and cleaning between each group, then measure each group and average all 4 of them, this will tell you the true potential of the load consistency
in my opinion.

Hunting requires a different kind of testing in my opinion than targets and loads must be developed for each type of use for best results. Test for the way it will be used.

Just my opinion

J E CUSTOM

 

[Wolf76]

I'm more of a 3-5 shot group testing person - but I validate the groups by repeating the test 4-5 times on different days. For hunting the cold bore shot is the most important, but consistency is almost equally important.
I've always laughed when people say they have a .25-.5 MOA gun. Because the justification is the ONE group that shot that well, while ignoring several groups that were 1+MOA.
I've learned in Michigan that "tack driver" means something less than 3 MOA. My guns shoot consistently less than .75 MOA- with a couple being sub .5 MOA, but that's with extensive reload tweaking and a ton of time at the range.

Back to the original post - great analysis and thought provoking ideas.

 

[thwatson2]

I think the big question is what MOA is the shooter. I hunt with guys who make a $10k custom rifle look like a Chinese Mauser. They have hard time hitting 9 inch plate at 100 yards. Then some can take same rifle and make a cloverleaf.

 

[Pointman]

IMO, I believe the "cold bore" first shot should be the best data for a hunting rifle. As mentioned above, it's rare to shoot 3 at a game animal. From my experience, and every rifle is a law unto itself, group size should be measured according to the shooters' type of shooting. Bench rest will need more to determine their optimal load. The same may be applied to varmint hunters. My 338 LM habitually shoots the first round dead center then as the barrel heats the shots go a bit high and left, still well under an inch. Using a Chamber Chiller help with that beast. I have a custom barreled 25-06 with a Douglas supreme barrel built in the early '70s with a crown the same diameter as the receiver end. That one takes a while to heat up so multiple shots will have a similar impact point. It was built for chuck shooting from the hood of my truck. At 17 pounds, I don't carry it far. At the range, I will shoot no more than 10 in a row with 2 for warm-up then 5 for a group, the last for "grins" at a long-range gong.

 

[speedengineer]

Nice write up. I use 3 shot groups in my load development. By time I'm satisfied with a load, I end up having 4 or 5 sample groups which were shot on different days and conditions. I overlay them to compare a few parameters and they end up (or should end up) being very similar. I also like to read the hit probability articles over the PRS blog.

Thanks for mentioning this! I hadn't been to that site before - lots of good articles there.

It looks like others, particularly Bryan Litz, have published lots of info on these sorts of topics. His WEZ tool looks very powerful, hadn't seen that before. I have a similar tool I made in Excel, though it's more simplified (only considers the effects of cartridge, rifle precision, range uncertainty, and wind uncertainty. Perhaps I'll share it here on LRH if people are interested. The AB WEZ tool looks awesome, but too pricey for me!

 

[LVJ76]

Thank you for the analysis Engineer, really good information.

Stay safe

 

[VLD Pilot]

10 shot groups are how I tell what the gun and me are capable of. Not just the gun. It's always me behind my rifles so that's my accuracy standard. All my rifles are under 1 MOA. If I shot 3-5 shot groups, most would be under .25. I don't believe it's ONLY the gun that counts in the formula. As stated by another, I'm well within minute of animal I'm hunting so no worries.

 

[LRNut]

Not sure what range you guys test loads, but my LR gun load dev is done at 500 yards. If it doesn't shoot a three shot 2.5" group, I am not interested. Today I tested two 28 Noslers; both groups were almost identical - 2.035" with all of that vertical. Both groups had two bullets touching. Had about a 4 mile per hour wind but it was consistent, and drift was pretty much exactly what my SIG Kilo 2400 AB said it would be.

 

[LRNut]

Thanks for mentioning this! I hadn't been to that site before - lots of good articles there.

It looks like others, particularly Bryan Litz, have published lots of info on these sorts of topics. His WEZ tool looks very powerful, hadn't seen that before. I have a similar tool I made in Excel, though it's more simplified (only considers the effects of cartridge, rifle precision, range uncertainty, and wind uncertainty. Perhaps I'll share it here on LRH if people are interested. The AB WEZ tool looks awesome, but too pricey for me!

I am also intrigued by WEZ models, especially when it come to allowable wind error. A lot of shooters think bullets all travel in a straight line, and thus a rifle that shoots 1 MOA is theoretically good enough to hit a 10 inch target at 1000 yards. However, doing so would require a perfect wind call every time. If you do the math, a .25 MOA rifle has a lot more allowable wind error than a .75 MOA rifle. This exercise will also get to realize just how precise your wind call must be to hit a foot sized target at 1200 yards.

The PRS Blog is a good site, but I wish it was current. 2014 was six years ago.

 

[judgebill]

If I'm going to hunt big game I'm looking for a 3-shot group that is consistent. That is, when I take my rifle to the range, It will put 3 shots, including the first out of a cold bore, into an inch at 100 yards. Assuming I have shot at extended ranges and found consistency (using my 3-shot approach) I can be confident that if I do my job, the rifle will hit what I'm hunting. Now, for my varmint rifle (22/250) I need consistency over many more shots, depending on what it is I'm shooting. For ground squirrels and rabbits and, if I'm lucky, more than one coyote, I need a rifle that will shoot many more than 3 shots. And if I'm shooting just for target accuracy I'm looking at another approach. This analysis that Speed did was great and helpful. This whole forum is great and helpful. Thanks to everyone for their contributions on this subject.