Advanced Marksmanship Zeroing rifle

[dar1246]

I recently zero my rifles before going to a match. A lot of snow drifts. So I set the target in the low spot a 100 yards away. When I shot the match I shot high on all my dope. Could not figure this out. Got back to the house and looked at my target. It was placed at a 7 degree angle for my shooting bench. Shoot the gun at a level 100 yards and rezero the gun. How much do you think this would have an effect on a shot at 800 yards? Or do you think this would not have any affect on the bullets impact.

 

[memilanuk]

Re: Zeroing rifle

Did you zero from the same position as you shot the match?

 

[dar1246]

Re: Zeroing rifle

No. We shot mostly flat ground.

 

[Breeze260]

Re: Zeroing rifle


What was the temp when you zeroed versus when you shot the match?

 

[dar1246]

Re: Zeroing rifle

Pretty much the same conditions, pressure,hum,alt(1785 to1328),temp. Even shot the same back at the house. Ran a test on the zero.

 

[Breeze260]

Re: Zeroing rifle


Hope this helps

http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=935958

 

[dar1246]

Re: Zeroing rifle

That explains the angle of the shot. This is understood that the shots will hit high, so aim low by the right correction.

But if you sight your rifle in at an angle at 100 yards(thinking your rifle and data is dead on). Would you dope be the same shooting at farther distances?

 

[Breeze260]

Re: Zeroing rifle


My understanding is that you did not sight your rifle in at a 100yds because of the angle, it was less than a 100. By how much I don't know. So that should put you low not high so I don't think that was the issue. I'm starting to get myself confused

 

[dar1246]

Re: Zeroing rifle

I sighted the rifle in at 100 yards with and 7 to 10 degree angle. I did not think about it. Went to the match and shot. My dope was off. Came back home shot the gun at 100 yard with no angle. Do you think this would make a difference. A buddy of mine argues that it wouldn't. So I tested the zero.

question is Do you think it would make any difference to sight a rifle in at 100 yards at an angle. Then shoot 600 to 800 yards with no angle.Would there be a difference between angle zero at 100 or zero at 100 with no angle?

 

[Breeze260]

Re: Zeroing rifle

Yes
but how do you know the angle?

 

[Breeze260]

Re: Zeroing rifle

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dar</div><div class="ubbcode-body">I sighted the rifle in at 100 yards with and 7 to 10 degree angle. I did not think about it. Went to the match and shot. My dope was off. Came back home shot the gun at 100 yard with no angle. Do you think this would make a difference. A buddy of mine argues that it wouldn't. <span style="color: #CC0000">So I tested the zero</span>.
</div></div>
Was there a difference?

 

[dar1246]

Re: Zeroing rifle

1/2 to 3/4 moa difference. I shot 5 of my rifles and all was off. I re-zeroed the week before. Now the data is dead on. The will affect the shots taken at longer ranges. From now on set my target at the same level as my bench for a zero.

 

[memilanuk]

Re: Zeroing rifle

Any barometric changes from when you zeroed originally to when you shot the match? Not just 'altitude', but actual pressure?

 

[dar1246]

Re: Zeroing rifle

I use a Krestel 4500 for this reason. Question is the difference in a 100 yard angle zero.

 

[memilanuk]

Re: Zeroing rifle

Sorry... I was trying to suggest other things that *might* actually make that much difference from one day to the next. IMO that small of an angle should not have any meaningful difference in the real world. In theory according to JBM it should account for about 3" plus a little bit @ 800yds for a 10° angle... for a .308 lobbing a 185gr pill @ 2700fps. For a 155.5 @ 2960fps it'd be about 2.5". For a .260 or whatever it is you're shooting... probably even less. The day to day atmospheric variations and changes in shooting position, etc. will probably swallow that small of a change anyway.

 

[dar1246]

Re: Zeroing rifle

No reason to be sorry. I tried the JBM but when shoot the impact was off on 5 rifles almost the same amount of moa at 100.

 

[CoryT]

Re: Zeroing rifle

10 degrees at 100 yards will change the POI by .1 MOA. less than 1 click, so the angle to your zero target was not the cause of your error.

 

[dar1246]

Re: Zeroing rifle

I will test this theory again. I will post the results for the targets. I will shoot 2 rifles on the same day. I will set 2 targets up different angles at 100 yards.

 

[Lindy]

Re: Zeroing rifle

To reinforce what Cory said, the trajectory of a .308 with a 100 yard zero is flat - within 0.1 inches - from about 70 yards from the muzzle to about 109 yards. So, that slight angle in the zero is not going to make any significant difference.

 

[dhutch]

Re: Zeroing rifle

I'm just thinking out loud here, but...

If you were zeroing your rifle at 100 yards with a 7 degree angle, that would be more like zeroing your rifle at 99.25 yards with no angle.

If we apply that standard to a 800 yard shot....
Take your same error....you would need to dial in at 794 yards(with a 7 degree zero @100) in order to hit a 800 yard target on a flat surface.

If you didnt make those corrections at your flat 800 yard shot...you'd be shooting almost 5inches high.

The error is almost mute at 100yards.....but when you get out to 800 yards, that error multiplies big time.

Not quite sure how high you were shooting at all the other ranges, but this could be your problem for the 800yard shot.


Or is this completely off base in this situation?

 

[dar1246]

Re: Zeroing rifle

Lets say the angle of the shot does not make that difference. I don't think in 100 yards the pressure, humidity,temp would make a 1/2 to 3/4 moa change. Most of the weather conditions was about the same. I will shoot the same targets again and see the difference. I do understand what everyone is saying but can't figure out why?

The angle is the only thing that was change. The target that I moved went about 12 feet higher than the target shot the first time.

 

[dar1246]

Re: Zeroing rifle

I zeroed my rifle in on level ground. Then shot at a target set up. From my bench to the target is about 20 feet of height difference out to 100 yards. Here is a picture of the target. The target on the right is first 3 shots at the target. The target on the left I corrected my scope by 1/2 moa. This rifle was dead on at 100 yards on level ground.

 

[Lowlight]

Re: Zeroing rifle

The angle is not the only thing changing, it could be how you are looking through the scope, or the fact you don't have the parallax adjusted correctly that will cause the shift that you don't see.

if you are putting your head in a different place to account for the rifle being in the same place but the target being in a different location, and you haven't adjusted the parallax properly, you have a potential for a problem.

As well if your not getting the proper sight picture and there is a small amount of shadowing that will move the impact.

 

[Lindy]

Re: Zeroing rifle

What Frank said.

The difference of a half MOA at 800 yards would be about 4 inches - if you could hold a half MOA at 800 yards.

I can't. And most people have trouble holding a half MOA at 100 yards.

 

[dar1246]

Re: Zeroing rifle

Here is my point of this. When I shot the other day. My come was 18.8 at 800 yards. I looked downrange and knew there was a slight angle to the shot. I adjusted for the shot an 1/2 for the angle of the shot. I shot over the target. I adjusted another 1/2 moa and hit.
When I shot tonight. I shot 3 shot groups so that I would show that it isn't just 1 shot. The group on the left is about a .200 group at the angle shot. I then shot at the same angle shot to see what it would take to bring it to a zero. I adjusted my scope by 1/2 moa and shot 3 more times. I shot 1 lower. I think this is what Lowlight is saying. Lowlight one thing I have learn from your online training is to run through the list to wipe all variables you can away. This has made me a better shooter by far than I was.

I ran ballistics program. It takes up to 14 to 16 angle to make a change in the bullet impact. Maybe I'am to dumb to figure this out but this is my results.

Lindy I can't hold a 1/2 moa group out to 800 yards but I can hit a 12x12 steel target at 800. No disrespect intended. I do agree with both Lindy and Lowlight.

I test this theory again.

 

[Lowlight]

Re: Zeroing rifle

Have you tested your scope to make sure it is tracking correctly over distance. Meaning the entire distance traveled.

As well at 800 yards, environmental conditions can give you a 1 to 2 MOA difference in your dope from one day to the next.

 

[dar1246]

Re: Zeroing rifle

I mostly shoot 600 to 800 yards. I shoot some F-Class matches in the summer. I shot a lot at my range at the house and it seems to track great. When I bought this scope it was a S&B and tested at 100 yards to see what the hype was about. It seem to track great. I'am no master shooter but by my judgement it was fine. If I hit to the left or right. I adjust and if I'am holding the rifle. The bullet impact goes where it was intend to impact.
I figured the conditions would have some to change the impact but not at 100 yards. When I shot at the target at 800 yards. I did a 1/2 correction for the angle of the target. I always check my Krestel to see what the differences would be. Then I run it through my program and see if there needs to be a correction from my dope. In this case there was no change in my dope. The conditions was very similar.

This is why I went to 100 yards to see what was going on. To many things can be the problem at 500 to 800 yards to put a finger on it. This is the only element that has changed. This winter had to move my target to a lower area because of all the snow drifts was 5 ft deep. Before this my zeros was on with my dope.

 

[Lowlight]

Re: Zeroing rifle

I hate to say, if its not the shooter, like what I said with the parallax, and its not the scope tracking, it may come down to the rifle not being as well made as one would like. It could be an issue in the bedding, something in the rings, base, or otherwise.

We see it classes all the time a certain percentage of rifles that need to be re-zeroed almost daily as they move and slip slightly.

I haven't pinpointed the problem exactly it could be inconsistencies in the shooter, or something in the rifle but we see it every time we have a class. May rifles when used routinely slip off target.

 

[dar1246]

Re: Zeroing rifle

It still could be the shooter. I'am by far not perfect but try to be. It maybe the parallax or the rifle. I will go through and check all the inch pds on the screws and things. Thanks for the help.

 

[dar1246]

Re: Zeroing rifle

I checked everything last night. Scope rings,bases,stock with my Inch pd wrench. All checks out. I didn't have a problem with the zero being off. The gun once sighted in stays on.

I will do another test. I would say, if the results come back the same. I like I heard once the bullet don't lie. Here is the example, From my bench to target is 100 yards. There is a 22 feet difference in height between the target and my bench. If you can hold a tight group. Then shoot and test it yourself and see what happens.

 

[dar1246]

Re: Zeroing rifle

Well the here story is. I found out tonight that my target is not at 100 yards. It was setup at 90 yards with a 7 degree angle. Went through the list and everything checked out. Laser the target and found out my boy set the target a little closer, so he wouldn't get into the snow.

I do apologize Lowlight and Lindy is spot on as usual. My thoughts on the matters is put to bed. Now I don't have to keep racking my brain why??? It is the little things in life you got to like.