Determining firearm group size

[Doc Highwall]

When first working up a load (mostly rifle) I have at least a 100 cases that are within a accepted weight variation depending if it is a hunting rifle or a target rifle. I then load 50 rounds starting 10% below the maximum powder charge with 5 rounds while working up in 1% increments of a greater powder charge for 5 rounds each till I have all 50 rounds loaded. This will give me 10 loads of 5 shots each that will be shot at 100 yards. After going over the group sizes and chronograph data I determine what is close to the best load and will now load at least 20 rounds of each and now test at 200 yards. The testing at 200 yards will be 4 groups of 5 shots each, because shooting 5 shots and taking a short break between will allow the level of concentration to be maintained. Now the best load will be tested at 300 yards again with 4 groups of 5 shots each playing with seating depth. When this is done I start shooting 10 shot groups and then 20 shot groups.

[MT Chambers]

Do what most people do on these sites, measure ctr. to ctr. of the 2 furthest apart shots then subtract 2", that's the group size.......oh and mention that the guns shoots those groups "all day long".

[Hannibal]

Do what most people do on these sites, measure ctr. to ctr. of the 2 furthest apart shots then subtract 2", that's the group size.......oh and mention that the guns shoots those groups "all day long".

On some sites, yes, EXACTLY. But don't forget the 'If I do my part' line.

[fredj338]

Handguns, 5rd groups, small bore rifles (30cal & under) 5rds, medium & large bore (33cal & over) 3rds is enough. Two groups makes an avg, but the more the better. Splitting the shooting up over more days can be a better test method, but does rely on you having yopur best days on the trigger every day. I don't count fliers in the group, but note it in my data, like 2" group, 4 in 1". Then often will reshoot that combo to see if it was me or the gun/load.

[Hannibal]

My rifle will shoot sub-MOA all day long...for real...if'n I do my part...3 shot groups.

Never ment to imply no one could. Just find it difficult to believe every novice shooter with a computer and a new rifle can. First trip to the range. With the first box of ammo they happen to grab. Hmmm . . . .?
Or maybe I just have the worst luck ever buying firearms and ammo . . . ?

[MT Chambers]

I use paid (or bribed) witnesses, for all my .5" groups, all day long!

[shooter93]

Well LL....I'll go you one better....my guns shoot 1/4 moa all day long and I always do my part......smiles.

[fredj338]

Never ment to imply no one could. Just find it difficult to believe every novice shooter with a computer and a new rifle can. First trip to the range. With the first box of ammo they happen to grab. Hmmm . . . .?
Or maybe I just have the worst luck ever buying firearms and ammo . . . ?

Back when, I let my 16yr old son shoot my precision rifle for the first time behind a scoped centerfire. He printed a nice 3/4" group for 5 @ 100yds. yes I was impressed. FWIW, that rifle will shoot 1/2moa all day, several diff loads, with a good shooter & good conditions.

[fouronesix]

I like the banter about "if I do my part"!!! Or how about, getting all wrapped around the axle with so-so groups on a paper target but nonchalant like, "good enough for hunting" or "minute of deer".

Seriously as to the OP. I think about groups as a three part dependent triangle: Shooter, Load, Gun.

I have guns that simply will not, never did and never will shoot 1 MOA. But most of those are well over 100 years old with some over 160 years old. I have guns that were purpose built and if they don't shoot 1/4-1/2 MOA something is wrong. Everything has to be kept in context.

For assessing accuracy of a load/gun and I shoot three 5-shot groups on different days under decent conditions and that includes my condition, then I feel pretty comfortable the mean of those groups is about the base line accuracy of that particular load/gun. Some will say no way and may even call you out about it! Then proceed to rattle off a bunch of minimums of statistical confidence levels. Whatever. But, you can look at it conversely. What are the chances that three 5-shot groups will measure such and such by some sheer fluke of coincidence??

[Hannibal]

I like the banter about "if I do my part"!!! Or how about, getting all wrapped around the axle with so-so groups on a paper target but nonchalant like, "good enough for hunting" or "minute of deer".

Seriously as to the OP. I think about groups as a three part dependent triangle: Shooter, Load, Gun.

I have guns that simply will not, never did and never will shoot 1 MOA. But most of those are well over 100 years old with some over 160 years old. I have guns that were purpose built and if they don't shoot 1/4-1/2 MOA something is wrong. Everything has to be kept in context.

For assessing accuracy of a load/gun and I shoot three 5-shot groups on different days under decent conditions and that includes my condition, then I feel pretty comfortable the mean of those groups is about the base line accuracy of that particular load/gun. Some will say no way and may even call you out about it! Then proceed to rattle off a bunch of minimums of statistical confidence levels. Whatever. But, you can look at it conversely. What are the chances that three 5-shot groups will measure such and such by some sheer fluke of coincidence??

My method is quite similar, only I insist on 10 shot groups. Most everyone who knows I do this say I'm crazy.
Perhaps. But if I say a rifle will
hold such-and-such group size, I have yet to be embarrassed.

Heck, even a broken clock is right twice a day.

[MBTcustom]

You are starting to smell the stench of big fish stories vs. reality.
If accuracy is measured by the best three shot group one can produce in ten tries, then nearly all factory rifles are sub MOA. Had a guy in the shop that actually carried a 1" three shot group in his wallet and had it laminated. I asked him where the other 7 shots went? LOL!

If you measure group size by ten shots, then you've got about a 90% idea of the accuracy potential of that rifle. If you fly 25 into the same group, I'd put it at 99% certainty what your particular bullet hose is spraying.
I really do think of it like the nozzle on a water hose. Each combination is going to produce a certian effective cone of spray. I'm sure all of you have played with those cheap water nozzles for the garden hose and tried to make it spray as tight a stream as possible? Remember how some times going all the way down and then backing up would make the stream the tightest? Or maybe you twist the nozzle handle with your palm just so? It only ever took about 5 minutes to find that sweet spot where you could get the angle just right to soak your unsuspecting brother or sister down and then drop it an run like hell.
Well that five minute education you just got was the equivalent of 500,000 rounds of ammunition if you could control the loads with a nozzle! (personal fantasy, God I wish I could manipulate powder burn rate's that easily!)
So if you expect to achieve the same effect in less than 100 rounds, you had better be paying attention to your load science.
That said, I gave up on factory gun barrels a while ago (with very few exceptions, none of which are produced in america). You start grabbing random rifles off the shelf and doing load workups for them, you quickly learn how rare it is to get one that will hold up to three ten shot groups. Most factory rifles are held to the same accuracy standard mil-spec rifles have been held to for the last 300 years: 4MOA. Anything better is gravy.

Now, you buy one of those "overpriced barrels" from Krieger, Brux, Bartlien, Broughton etc etc etc, (claims the guy who has spent how much on reloading components, gas and range fees trying to fool himself into believing he has an accurate rifle?) and you have it screwed into the same action, suddenly your potential group for three tens goes down to around a true 1 MOA potential.
Some out there are saying ohhhhhh. So you're talking about consistent potential. Man. That sucks.
To which I would reply: It doesn't suck per se. It's realitity. It's either able to be reproduced on demand or it isn't.
Oh and a word on fliers: Quit calling yourself a lousy shot and ignoring those fliers!!!! If I put any one of you behind a true target rifle, you would be able to shoot ten times better than what you do with your cheap wal-mart special. No fliers. There is no such thing. The rifle shoots where you aim it. Period. If you aimed at the bull and your bullet hits 2" to the left, that was the gun trying to tell you something!!!
I am speaking from experience here. I used to play all these silly games with myself. Started building custom rifles and found out, I'm not such a lousy shot after all. Turns out, I use to think I was good for 1MOA and anything else was the rifles fault (that is so embarrassing to admit now, but it's the truth, and I suspect many here are doing the same thing)
Turns out, on a good day, I'm good for 1/4MOA because I can shoot 1/2" groups with a rifle that is good for 1/4" groups. Nice!

By far, the worst personal detriment to accuracy that I have found is lack of sleep. Shooting takes concentration of enormous proportions and if I'm unrested (pretty much the daily battle around here) I have a really hard time.
For instance, I went to the range tired and just couldn't shoot better than 4MOA with a rifle that I built and I knew was good to 1/2MOA. That sucks!
But even when I was tired, that gun shot where I aimed it when the trigger broke. The last thing I saw in the scope was the crosshairs drifting off the bull and surprise surprise, the shot punched the target right there.

This is the point: Yeah, the group on paper is a representation of the shooter, the loads, and the rifle, but a good rifle with decent loads and even a novice shooter who's not going to sleep behind the rifle, is able to drill 1" groups all day long.
If you can't ever get there after changing the loads, then it aint you. Either you're a total goofball all the time, or you have a janky factory barrel on that gun like everybody else does. Yeah, there is probably a load out there that will get you better results, but if you ever screw a decent pipe on that gun, you'll find that it wants to shoot darn near anything under a 1" group at 100 yards, and your best loads will be one holers. If anybody says different, I want to see the 10 shot group. Show me three subMOA tens overlapping and I'll buy you lunch (just let me get my notepad LOL!) but this three shot 1MOA group kept in a wallet isnt worth the paper it was printed on.

[Hannibal]

I had been wondering how many shooters have been chasing the 'cast boolit load unicorn' with a firearm that simply was not consistent enough to give consistent results.

[tygar]

This is a very open ended question & can have many different answers.

e.g What gun & for what use? Is it my M99 30-30, then once it's on paper ladder with 3 shots then take the best & do 5 shots at 100. THen take the best & shoot at 150.

If it's my Spencer 1000yd heavy gun with Batt action, probably know where to start & shoot a 5 rd group at 100 to get zero, then 5 at 200, 300, 400 to ensure computer & rifle are the same. Then 10 rounds at 500-1000. Then various days at various distance. Then there are Fclass, sniper, hunting, etc.

Before all this, there is the matching brass wt to .3-.5 gr depending on size, bullets exactly the same, primer, power exact etc.

Lots of variables.

Combat guns, hunting, plinking, target, each has it's own rules.

If its a 40 or 75 # heavy gun no excuses, light gun the same, but a called shot out may be discounted but not usually. A sneeze is always an excuse. lol

So what I do depends, depends on the rifle, it's use & whether I'm working up a new load or just confirming zero & group.

If it's cast bullet rifle I'm still learning & would count 3 shots in an inch a good group, but I am doing the 3 shot/5 shot ladder but starting at 50yd-150.

Pistol, cast & jacket, rev all 6, 5 times at 25 & 50, autos the same except only do 5. Hunting or long range the same out to whatever distance is max.

[dtknowles]

For bragging 3 or 4, 5 shot groups at the appropriate range for the firearm. Handguns, 25 or 50 yards. Long guns 50, 100, 200 or more.

But what is the point except for bragging. 10 shot groups tell you more but of course are bigger so not as good for bragging. 4, 5 shot groups is 3 ten shot groups if you over lay them, the first with the second, the second with the third and the third with the fourth.

Depending on the purpose of the gun, the shape or pattern of the groups can be important. Plinking, big game, varmints, targets, groups.

When I am testing most often I am not testing the firearm, I am testing ammo. I quickly find out whether the gun is suitable for its task and after that I am testing ammo to decide what I will load for that gun.

When I am bragging about my shooting I prefer to brag about my ability to shoot not about the gun. If you are bragging about a cheap gun that shoots good then you are bragging about being lucky. If you are bragging about an expensive gun that shoots good you are bragging about all the money you spent (if you built it yourself, that's a different story). If you are bragging about standing at the firing line and putting 10 in a row into the 10 ring at 100 yards you might be bragging about your ability.

If you want to brag about groups, your better have more than 1 and they better have at least 5 shots.

Tim

[Hannibal]

Well, now. THAT'S certainly something you don't see everyday.

[dtknowles]

It is when Tim Malcolm works his magic on a rifle.

Back to your OP and determining group size. That is easy, outside to outside and subtract bullet diameter.

Now figuring a rifle's average group size is going to require you to shoot several 10 shot groups with the same load and then take the average.

What is acceptable depends on the rifle. For a woods bumming truck gun like the M4 and others, I am happy with 3 MOA or under as 3 MOA equals hits on man size targets to 600 yard.

For a match rifle it needs to stick 1 shots sub MOA every time if'n I do my part (seriously). You can get fatigued behind a rifle so when doing load development it may take me a couple days to shoot my test ladder of 10 shot groups of powder charges.

Averaging several 10 shot groups will get you an average 10 shot group size which is larger than a rifle/loads average 5 shot groups size. This will not be the rifle's average groups size it will be the rifle/loads average groups size. It is not all about the rifle, the ammo gets some credit. If it was all about the rifle it would be an average of groups shot with a variety of ammo.

I don't see how "3 MOA equals hits on man size targets to 600 yard" for a "For a woods bumming truck gun like the M4" out to 600 yards in field conditions even with a range finder and a rolled up coat on the hood of a pickup truck that mansized target better be presenting a full face on target and even then that 18 inches of dispersion is going to mean some misses and many no lethal shots. That is not even counting for misread on the wind. Even two MOA will not guarantee a lethal shot on a man at 600 yards in field conditions.


I thought that the ladder test was an alternative to shooting groups to find the best powder charge. To quote your from a previous thread "I use it all the time. It gets me out to 1,000 yds with very minimal work and eats up significantly less components.

You do not shoot a group of rds at each powder charge. You shoot ONE rd at each powder charge.
Ladder testing at 100 yds is pointless for a centerfire (using jacketed).

The Snipers Hide ladder test is the best example floating around the net. There are some very serious shooters on that forum."

Tim

[Love Life]

Averaging several 10 shot groups will get you an average 10 shot group size which is larger than a rifle/loads average 5 shot groups size. This will not be the rifle's average groups size it will be the rifle/loads average groups size. It is not all about the rifle, the ammo gets some credit. If it was all about the rifle it would be an average of groups shot with a variety of ammo.

I don't see how "3 MOA equals hits on man size targets to 600 yard" for a "For a woods bumming truck gun like the M4" out to 600 yards in field conditions even with a range finder and a rolled up coat on the hood of a pickup truck that mansized target better be presenting a full face on target and even then that 18 inches of dispersion is going to mean some misses and many no lethal shots. That is not even counting for misread on the wind. Even two MOA will not guarantee a lethal shot on a man at 600 yards in field conditions.


I thought that the ladder test was an alternative to shooting groups to find the best powder charge. To quote your from a previous thread "I use it all the time. It gets me out to 1,000 yds with very minimal work and eats up significantly less components.

You do not shoot a group of rds at each powder charge. You shoot ONE rd at each powder charge.
Ladder testing at 100 yds is pointless for a centerfire (using jacketed).

The Snipers Hide ladder test is the best example floating around the net. There are some very serious shooters on that forum."

Tim

Do you even shoot, Bro?


All info deleted.

[dtknowles]

Do you even shoot, Bro?


All info deleted.

I was tops on my high school shooting team my senior year (38 years ago). I shot some NRA Hunters Pistol matches for a few years. I shoot at least every other weekend. I have posted targets here for some of my range time. I will be shooting my 6mm PPC benchrest rifle tomorrow. I cast too, pic's of some of my bullets have been posted here as well.

Tim

[btroj]

In the end all shooting is judged one shot at a time. It either goes where it is supposed to or it doesn't.

I tend to use 5 shot groups because they work for me. I don't care what others use or why, I don't shoot to prove anything to them or make them happy.

Do what makes you happy and never look back.

[Love Life]

In the end all shooting is judged one shot at a time. It either goes where it is supposed to or it doesn't.

I tend to use 5 shot groups because they work for me. I don't care what others use or why, I don't shoot to prove anything to them or make them happy.

Do what makes you happy and never look back.

I much mo' betta' understand yours and Gear's absence more and more as the days go on.