New member Q -- How Many Shots to Set Zero?

[stats_guy]

Hello form Los Angeles! Finally made an account after reading many posts on here. Been shooting a 223 Rem bolt gun (Tikka T3x) for a couple of years, stretching it out to 1000 yds whenever I get a chance, and looking to build my first dedicated target rifle soon.

One thing I've been curious about is how many shots everyone uses to establish their zero for a particular ammo/load. 3, 5 and 10 shot groups are common, but is there a crowd favorite?

And as a follow-on question - how often do you re-zero? Only when you change the load, any time the shooting environment is different (temperature, altitude, etc.), or some other factor?

 

[RegionRat]

Welcome to the forum.

Another "it depends" answer.

With a wide-open question, you could get any answer.

Sighting in some old relic with surplus ammo might take 15 rounds, and it doesn't matter how often you re-zero unless you are in the later stages of some matches with rules.

Same can be said for more accurate rigs. You may be happy with a no-wind zero after three shots, but that is only because you know you will be in a competition with unlimited sighters.

So in the context where a hunting rig or MIL/LEO context requires a perfect cold-bore shot, it would take several sessions on many different days with different weather, and with the cleaning regimen taken into account, to answer the question.

 

[Straightshooter1]

Hello form Los Angeles! Finally made an account after reading many posts on here. Been shooting a 223 Rem bolt gun (Tikka T3x) for a couple of years, stretching it out to 1000 yds whenever I get a chance, and looking to build my first dedicated target rifle soon.

One thing I've been curious about is how many shots everyone uses to establish their zero for a particular ammo/load. 3, 5 and 10 shot groups are common, but is there a crowd favorite?

And as a follow-on question - how often do you re-zero? Only when you change the load, any time the shooting environment is different (temperature, altitude, etc.), or some other factor?

Welcome to the forum. You'll find a lot of good people with a lot of experience willing the share and help (like above ).

Uaually, 2 shots get me pretty much zeroed. Then 3 more to find a groups center and make the minor adjustment, then I'm good to go.

I only have to adjust zero when changing the load (which can include a different bullet).

 

[Kracken McGraw]

Welcome.

 

[joshb]

Welcome to the forum. I challenge myself to be on in three. Half the time it works out OK. Sometimes the first shot doesn’t hit paper. Then it’s a job!

 

[Coyotefurharvester]

2 winters ago I "zeroed" a thermal scope in one shot. X,Y axis adjustment to the point of impact. I fired a second shot to verify. Than went 21 for 21 on coyote, first miss I hit an unseen strand of barbed wire at 2am(-20° F).

 

[Downhill]

2. Fire one. Hold original aim point. Adjust reticle to first impact- without disturbing rifle position. Fire second, if done correctly you'll be on your aim point.

 

[ELR LVR]

if I switch scopes, I bore sight, when looking through the bore, note it helps to understand how
peep sights work as the concept is the same, you must align your POA to be dead center in your viewing aperature
usually the first shot is within 6 inches,
Adjust scope a couple more times and it can be very close within 3 shots
A couple more fine adjustments and dead on in 5
--------
As for double checking your zero, it is more rifle dependent
I have one that can sit for a year and still be pretty much dead on if I break it out a year later
But that is a heavy rifle, heavy barrel, heavy stock etc.
While others may shift up to an inch after some time for whatever reason.
You will learn if you can trust your rifle to be on every time
and the only way to know is to double check your zero repeatedly in different conditions from season to season.
Some can shift POI due to weather, environment etc
--------
I feel it is wise to double check your 100 yd zero every outing.
You never know if a scope got bumped, came loose, etc. even in transit
it's rare but its 20/20 hindsight thing
You dont wanna say, "I should have double checked my zero" if the shot is important
if you are just paper punching you will be adjusting scope anyways so thats not a big deal

 

[ronsatspokane]

2 on occasion 3. After first shot hold gun at point of aim while dialing to where the impact was. Second shot is at point of aim. Gun needs to be very stable while dialing. If it is not, you may need 3 shots since you'll need to repeat the dialing process while holding the gun steady.

 

[DShortt]

2 on occasion 3. After first shot hold gun at point of aim while dialing to where the impact was. Second shot is at point of aim. Gun needs to be very stable while dialing. If it is not, you may need 3 shots since you'll need to repeat the dialing process while holding the gun steady.

This is my method also. If it's a new gun/scope I will boresight it with the bolt removed at 25 yards. Add another shot or two if that's the case.

 

[stats_guy]

Thanks for the replies all. Being a bit of a math/statistics nerd, I think about uncertainties inherent to finite-sample statistics a lot, which shooting groups is a an example of, hence my curiosity about the number of shots folks are typically firing to set their zero.

Part of the reason I wanted to start this discussion (maybe should've mentioned this in my original post..) was to share some of my findings from an app I've been working on. At its core it's a group analysis program that does a bunch of statistical calculations, and one of the outputs (alongside Mean Radius, CEP, etc.) is the Zero Uncertainty circle. Basically, it answers the question: how far from the group's center is the true zero likely to be, at some confidence level (say, 95%)?

This is calculated by treating a group as a normally distributed set of points in two dimensions, and using some standard statistical methods (in this case, the Hotelling's T^2 statistic scaled with an F-distribution) to calculate the confidence interval for the population mean, aka the circle that is likely to contain the true center of the system's "cone of fire".

A "typical" .77 MOA 5-shot group has a 95% zero radius of .54 MOA - i.e. the true zero is likely somewhere within .54 MOA of the group center. With a 10 shot, 0.83 MOA group (similar precision as the 5-shot group), the zero uncertainty radius shrinks down to 0.24 MOA.

I've included a screenshot from the app to show what it looks like (the white circle around the center is the zero uncertainty circle).


Of course, the application for the rifle dictates how much this matters. Being off by 0.24 MOA is likely totally acceptable for the majority of use cases, outside of maybe ELR shooting, and for many applications 2 or 3 shots are likely more than enough. But I figured folks here would find this interesting.

Finally, I'd like to gauge interest from the seasoned shooters here on a feature like this. Would you find a "Zero Uncertainty" output to be useful when you're doing group analysis or trying to characterize your system's accuracy/precision?

 

[jackieschmidt]

I am a Short Range Benchrest Competitor, mostly Score but occasionally Group.
I am always taking barrels on and off for what ever reason.

I am also pretty good at bore sighting by lining the bore up on a spot then moving the scope to it.

I can generally have it where I want in in no more than four shots.

How often I adjust the point of aim depend on the conditions I am shooting in to.

 

[charlie b]

For a new setup I do as Jackie. Pull bolt and look down bore. We used to do the same thing in tanks years ago. There were punch marks on the barrel to put a cross hair of string. Pull the firing pin from breech and look through it with binoculars (one side of course). That would get us pretty close on the 1000yd tgt.

If I am being stingy with ammo and the barrel is an unknown I will then shoot three. Adjust sight to group center and shoot a verification. Done. Of course that assumes you have a scope that tracks properly.

If you want to discuss statistics look for the threads on group sizes, es and sd. There are quire a few statistics types in here. Basically, most of us who shoot for smaller groups use the statistics whether we want to or not And, yes, the age old question is how many samples does it take to get a valid distribution for any given set of variables.

There are also already shot group analysis apps out there so you might want to look at them. I believe the Shotmaker has that function built in to their target software. GRT (internal ballistics software) has such a function in their program if you choose to set it up.

 

[Fuj]

I'll generally use 6 shots. I'll bore sight at 100 yards using a 12 inch circle
on a large sheet of card board. Adjust scope to it and fire a shot. Adjust
scope to that hit and fire two more. Adjust scope again if needed, then
go to a clean target to fire a three shot group.

Note.....I'll foul the barrel with two shots before starting, so call it eight
shots total. My method.

 

[Coyotefurharvester]

With firearms that have larger/looser groups, more rounds are needed to find the true center of the group. No app needed, just careful measuring and a bit of math(scope turrents must adjust and hold properly). This would be typical of factory hunting rifles/factory ammo. Opposite rifles that consistently group under 1/2 moa, very easy to zero.

 

[Forum Boss]

Here is a procedure for zeroing rifle in 3 shots from a bench:

1. First, remove the bolt and boresight the rifle. Adjust the position of the rifle so that, looking through the bore, you can see the center of the target with your eyes. Secure the rifle in the rests to maintain its position as boresighted. Then, without moving the rifle, center the reticle. That should get you on paper. With the rifle solidly secured in front and rear rests or sandbags, aim at the center of a target placed at your zeroing distance (50 or 100 yards). Confirm there are no obstructions in the barrel! Then load and fire SHOT ONE. Then, return the gun to the exact position it was when you pulled the trigger, with the cross-hair centered on the target as before.

2. Locate, in the scope, where your first bullet landed on the target. Now, while you grip the rifle firmly so it doesn’t move, have a friend adjust the turrets on your scope. While you look through the scope, have your friend turn the windage and elevation turrets until the cross-hairs, as viewed through the scope, bisect the first bullet hole on the target. Use the turrets to move the center of the reticle to the actual position of shot number one. IMPORTANT: Dial the crosshairs to the hole — don’t move the rifle.

Watch NSSF Zeroing Video showing method of moving reticle to Shot 1 Point of Impact.

3. After you’ve adjusted the turrets, now re-aim the rifle so the cross-hairs are, once again, positioned on the target center. Keep the rifle firmly supported by your rest or sandbag. Take the SECOND SHOT. You should find that the bullet now strikes in the center of the target.

4. Take a THIRD SHOT with the cross-hairs aligned in the center of the target to confirm your zero. Make minor modifications to the windage and elevation as necessary.

 

[memilanuk]

Finally, I'd like to gauge interest from the seasoned shooters here on a feature like this. Would you find a "Zero Uncertainty" output to be useful when you're doing group analysis or trying to characterize your system's accuracy/precision?

Going by the user name, I kind of saw this one coming.

The concept - and app - may be better received on someplace like longrangehunting.com, or Snipers Hide. This crowd here is the one that went into collective convulsions over Litz's book and Hornady's podcasts on group size and statistics. I'm not saying you're wrong... just this is probably not the audience you're looking for.

 

[stats_guy]

Going by the user name, I kind of saw this one coming.

The concept - and app - may be better received on someplace like longrangehunting.com, or Snipers Hide. This crowd here is the one that went into collective convulsions over Litz's book and Hornady's podcasts on group size and statistics. I'm not saying you're wrong... just this is probably not the audience you're looking for.

Haha, I certainly don't want to come off as preachy about statistics or anything, and I'm not trying to market my app (it's not available to download yet). I've found this forum to be friendlier in general than some of the other places, and it's great to learn about how people do things that's different from how I do them.

 

[charlie b]

... This crowd here is the one that went into collective convulsions over Litz's book and Hornady's podcasts on group size and statistics....

ROFLMAO yep.

Just read any thread about ladders or tuning loads. It is an art form for many and mentioning statistics or math is sacrilegious. LOL

 

[dellet]

Since statistics and life never match 100% of the time, rarely 95% of the time…….

If you shoot a 100 shot group, and randomly select 10, 10 shot or 20, 5 shot groups.
How many “true zeros” would your app show?
How many of those would be the same as the 100 shot “true zero”?
How far off would they be?