Is Zero on a scope shooter specific?

[JimStC]

Test results: 170 yards, factory ammo, light winds from behind us. Shooting from a sled

Scope set up for shooter #1
Shooter #1: .5 group.
Shooter #2: .675 group
Group to group: .49375"

Scope set up for shooter #2
Shooter #2: .5625
Shooter #1: .3125
Group to group: almost an overlap

Comments: very little variance and even from a sled with the barrel strapped down you still have operator input. This was an improvement but it may be due to Taliv's methodology which was spot on. Thanks Taliv.

 

[taliv]

Nice shooting there but what I was talking about is testing with no rounds fired. Just move your head around without touching the stock so the gun doesn't move and see if it looks like the crosshairs are moving or if it looks like they are staying on the target.

 

[JimStC]

Whoops.
I do think we are determining that p-adjustment is key as you suspected from the start. I have learned that p-adjustment is not without operator error though. We shot a lot more rounds to confirm our initial results and are still shooting. Just came in for some hydration

 

[taliv]

So if you are just turning it until it looks like its "in focus" then yeah the two of you are prob going to pick different settings.

But if you adjust it until you can move your head around and it looks like the crosshairs don't move then I bet it doesn't move for either of you and your groups are in the same spot

 

[JimStC]

Yep, the second round was almost an overlap.
Thanks for the patience.....
And yes,that is exactly what we did: Round #1: Shooter #1 adjust for their sight picture.
Round #2: Shooter #2 adjust for their sight picture.
The barrel was dead cold for round one. Pulled it out of the case and shot it. As the barrel warmed the groups constricted. Another thought...

 

[taliv]

No prob glad you got it sorted. Btw the adjustment on the ocular lens really is eyeball specific. To set it properly point the unloaded rifle at a clear blue sky and turn it until the reticle is in focus ignoring the background. Rest your eyes for a minute and do it again. Repeat a few times. Once you have a spot that looks good make a witness mark with fingernail polish or something so you can return it to that point. Then let your wife do same. The marks will prob be in different spots and that's ok. You'll be able to quickly return the scope to your setting when you swap.

 

[Jenrick]

Something people don't think about, because by and large it's not an issue is that it's possible to have a different "zero" for different positions you shoot the rifle from. While it's great to think that we always execute the fundamentals and always place our head in the same spot on the stock regardless of standing, prone, roll over prone, etc. the fact of the matter is that our eyeball ends up in a different spot.

Now for someone shooting A-zones, or even 6" head plates this isn't an issue, but what about 1/2" hostage targets in a LE/Mil setting? When the allowed error is approaching caliber size, it becomes an issue. The fractional differences between where you eye is located when shooting prone off a bipod, vs. roll over prone off a bag (say under a car) can mean just enough off a POA/POI shift to have dramatic consequences in the field. For the vast majority of shooters it doesn't matter, but for those who it does check your "zero" in different positions. Even doing the math for your dope when your rifle is turned 90 degrees will still probably leave you slightly off. It's not a matter of bad math, it's a matter of minute variances in head position.

-Jenrick

 

[taliv]

jim, check out the pics at these links. then go to www.precisionrifleseries.com and look at the event web pages. the pics below were taken by a competitor at my PMG match last fall. George Gardner of GA Precision took first place.

http://techtoyal.smugmug.com/Other/PMG-Fall-Match/19542190_W5kDdM#!i=1533792966&k=vnRv4JS

here's a link to several of his albums http://techtoyal.smugmug.com/Other

the website for my match/training company is in my sig. (click the results links at the bottom left hand and scroll down to see some stage descriptions and links to pics.

Zak Smith, another mod here, runs competition dynamics and is a fairly prolific photographer so you can find a ton of pics by following the links from his site http://competition-dynamics.com/

K&M is run by another friend of mine in florida. his website has some good info on matches and more pics http://kmprecisionrifletraining.com/

a bit closer to you is Tom Sarver's http://thundervalleyprecision.com/ he's a world record benchrest holder and runs some really fun but relaxed matches (all prone but long distance and usually high winds) in east ohio

there are a couple matches in missouri and I was just out last weekend in western oklahoma shooting the OPPS match, but I don't think they have websites. and yes, old guys do very well at some matches but not so well at others. some of the matches get pretty physical.

 

[Double Naught Spy]

Double naught what do you think causes that?

I don't know. Maybe next time we will work on the parallax issue and see if that resolves it as you suggest.

I realize it is not much, however, the further you shoot, the more error it will be! Also, the height of the scope from the center of the bore plays into this equation.

Actually, the error should be the same, being X degrees. The on target result with increase as distance from the target increases, but the error is the same.

When I look through some people's scope-rifle setups, I am amazed that some people can have the scope canted as much as several degrees (out of 360)! I wonder to myself, do they hold the rifle crooked so the scope hairs appear perfectly in-line or do they hold the rifle the way it "feels right" to them and that ends up being several degrees crooked with the crosshairs in-line!

A buddy of mine does this. He subscribes to the notion that making accurate shots consistently will be influenced by head tilt. So he cants the rifle a few degrees which are the degrees his head will be more upright. The scope isn't plumb with the rifle, but when he sights, the crosshairs are plumb.

The difference in the bore axis from the scope axis is about 3/4 of an inch. The scope axis is about 3/4" left of the rifle axis. So when he sights-in the gun or aims at a target, he does not put the center of the crosshairs on the point he wishes to shoot. He puts the center of the crosshairs about 3/4" left of where he wants the bullet to impact and his system works well for him.

What I don't like about his canting issue is that a gun canted to be fired right-handed won't work when trying to shoot left-handed.

 

[Dave P.]

I gotta say "maybe"
Short story....lotsa years ago we had a local shop with a 100 yard
underground tunnel range. In exchange for range time I would
"zero" guns they had mounted scopes on. Got to shoot lots of
different guns. Anyway I shot in a .300 Win mag with a 6 power
scope ( don't remember the factory load ). Customer ends up
bringing it back about a week later claiming it was off. I happened
to be in the range and the shop owner brought the customer and
rifle down and asked me to shoot it.
Got a box of ammo and put 5 rounds into about 1.5 inches centered
on the target squares. The customer looks through the scope and
asks what did I do to it?.....nothing?
He then gets on the gun and shoots about the same size group
about 5 inches left of the bull?
Don't really know why, but he had never fired anything other than
.22 rimfire and I think he may have had some kind of flinch
or shoulder twitch/jerk going. We just dialed it to where he was
happy. Didn't have time to work out the "why"
Dave

 

[Old Dog Man]

Point of impact

I understand you sight-in from a Caldwell rest, do you then shoot from a bag rest? If so that is why your sight-in is different, the Caldwell rest doesn't move like your shoulder does which will cause the grouping to move. Tried this on several different cal. rifles and it did the same thing. Groups didn't change, but impact point did. Al

 

[JimStC]

Yes, ODM. I do move from the sled to the bags. This thread has made me a lot more aware of my shoulder when I am on the bags. I try to make it the same every time which I know is improbable but at least I am now thinking about it.
Yesterday I had an interesting experience. I was shooting my Savage Model 12 Lo Pro in .204. Was shooting good sub MOA groups and all of a sudden the groups opened way up. I switched ammo to see if that was it. It wasn't.
I was right at 47 rounds. Brought the rifle in and cleaned it. Went back out and shot two sub MOA groups.
That sensitivity to a "dirty" barrel really surprised me. It was not like I had shot 1000 rounds through it dirty.
I was shooting factory ammo: Fiocchi (which the gun loves) and Hornady.
The groups started opening up after I switched to Hornady. Switched back to Fiocchi. Same result.

 

[NM Rancher]

Guys, this is just my opinion... I was shooting my m1a1 yesterday at 200 yards and was hitting dead center 6 inches high. I sighted the rifle in at 400 yards with a 3x9 bushnell. I hit 6 shots in a group of 2 inches, then I turned the weapon over to my father in law , who hit 3 shots 6 inches high , dead center at 200 yards. I think if the gun and scope are aligned right, anyone who looks through the scope and can shoot will preform with that weapon. The weapon and scope are tools, if they are properly set up I think they will produce similar results with a trained shooter.

 

[Old Dog Man]

Savage 204

If your barrel is new or fairly new it will take a while to slick-up the bore so it doesn't fowl as fast, shooting and cleaning after a few shots helps to smooth the riflings faster than shooting a bunch of shots. It will settle out after the bore is broken in. Al

 

[JimStC]

NM, I agree. I harken back to the old saying: "its not the tool its the mechanic". But what confuses me is that setting up a rifle and scope isn't exactly rocket science. I feel that I am competent to do that (don't we all?)
having done it for years. Heck maybe I have always done it wrong. Don't think so but don't know for sure.
Now to your last comment regarding a "trained shooter". That may be part of the issue. My wife is now learning to shoot. I have been working with her for several months. I do watch her mechanics when she is shooting and feel that she is moving along well: quiet upper body, nice trigger squeeze, no flinching and so on.
In any event, I get your point and appreciate your input

 

[JimStC]

Al,
We are getting ready to go shoot and I am cleaning both rifles before we go out.
Thanks a bunch,
Jim

 

[NM Rancher]

JimStC, I meant no insult about how you set up your rifle, nor your wife's shooting ability. If I came across that way I'm sorry. I was simply saying that the scope and the bore if properly aligned are going to place the shot where the mechanic places it. You and I know it varies on the wind the load and the bullet. I also have noticed , if the shooter that sighted in wears glasses it will change the view in the scope for someone who doesn't. Everything affects impact, I know I shoot out to 1000 yards! One day I'm hitting everything , and the next ... I'm needing a new scope! I think the secret is to love what your doing , and keep shooting!

 

[JimStC]

NM no offense taken at all. I was agreeing with your comments. I sincerely appreciate your input.
You make an interesting point that I have wondered about. My wife wears glasses and I don't. But, since we are adjusting for parallax, I felt we were taking that out of the equation. Maybe not.
Maybe Taliv will weigh in on this question

 

[taliv]

no idea on that one, but yeah, it is an interesting question

 

[chrome_austex]

In my experience, POI shifts from person to person exist due to differences in how the gun rebounds off the body of the shooter under recoil, so any differences in contact will change the POI:
* hands
* trigger finger
* cheek weld
* shoulder socket
* collar bone
* bipod or bags
* and flinching/anticipation

Its exactly the same as POI shifts from position changes.

Try giving a rifle zero'd for a right-handed shooter to a lefty. 9 times out of 10 they'll POI will be shifted right due to rebounding off the lefty's collar bone differently.

Other times you'll find that people's eyes perceive the somewhat fuzzy sight picture differently (mostly when using irons), or aren't lined up centered the same in irons/scope (parallax). Generally people should know how to center their eye to avoid parallax issues tho.

Two people with very similar and somewhat neutral shooting positions should shoot close to the same POI, but other people have trouble getting a repeatable position by themselves from session to session due to inconsistent position.

 

[JimStC]

Chrome,
That is exactly one of my issues: Shoulder placement and effect of recoil.
I am stocky with thick shoulders. My wife is small with thin shoulders. Once we get off the sled the groups do open up. But when we adjust for parallax the difference is minimized. It tends to minimize the shoulder issue. I am still not convinced that p-lax is the complete answer. We continue to shoot and evaluate the differences.
Interestingly, we were shooting her .17HMR yesterday and were grouping very closely as we each shot the rifle. Little recoil feedback with that caliber of course. Then we switched to 204 and still were both shooting sub .75 MOA. Then again, recoil is not a big deal with that caliber. We have a heavier caliber rifle coming. Should be interesting.
Thanks for the input

 

[taliv]

Perhaps the differences come from the different rifles we are shooting. In my case I've gone to considerable expense to get a quality stock and have someone who knows what they're doing bed it specifically so all those different thing DON'T make a difference.

I mean when I shoot off a barricade sometimes the whole weight of the rifle is on a vertical piece of plywood. or on bipods or shooting sticks. Sometimes I fold my bipod legs and throw my rear bag under them to rest it on a low wall or if I'm shooting under something and don't have room to extend the legs.

If each of those changed the poi there just wouldn't be much point in shooting.

I'm not saying anyone else is wrong here just that our experiences differ and maybe it's because of the way our rifles are configured or the way we shoot them. I don't know.

Maybe we should approach this in a more structured way and conduct some tests.

 

[JimStC]

Good point. All of my rifles are "off the rack" with no accurizing. I just adjust the triggers on the two Savage. That's it.
Another thought, and we raised this before, does the type of shooting matter?
I think we concluded that is does not, but it is still open for discussion.
For instance we are in a very controlled shooting enviroment. Does it matter??

 

[4v50 Gary]

I read somewhere that in pairing up snipers, they look for guys whose eye relief is the same. That way the scope won't need adjusting when they switch off between spotter and sniper.