I think this is the correct place to ask. I have searched and it seems fitment of the rifle may be the cause but I would like an opinion. Issue: from prone I have a good repeatable group centered at POA but from the bench my POI shifts left about 1/2" or so at 100 and 1"-1 1/2" at 200. Question: would too short stock cause this? The butt stock is adjustable for length and I have it set short as I prefer on other platforms. It is a new rifle, my first precision 308 bolt gun. I have only been the range with it twice. The simple solution would be to add spacers and shoot again but I will attend a class this coming weekend and will not be able to shoot again before then. I would like to have the rifle set up as well as possible so I can spend more time at class working on my issues instead of adjusting the rifle. Is it common for a too short of stock to cause a left shift when going from prone to bench or is this likely just poor form on my part? Also, prone will be the main shooting position, I only noticed the change because rain pushed me from prone on the ground to the bench under the shed. Edit to add: bipod used for both positions.
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POI change with shooting positions
- Thread starter two4spooky
- Start date
Re: POI change with shooting positions
I've read aticales about POI shift but I think it has to do with non-floated barrels mostly because of the force applied to it at different point. I've never seen it though.
I've read aticales about POI shift but I think it has to do with non-floated barrels mostly because of the force applied to it at different point. I've never seen it though.
Re: POI change with shooting positions
Kinda rifle are we talking about here? As asked above is your barrel free floated?
Kinda rifle are we talking about here? As asked above is your barrel free floated?
Re: POI change with shooting positions
It's not about positions, it's about perfect sight picture. And this has been covered here. <object width="425" height="350"> <param name="movie" value="http://www.youtube.com/v/Kzg_TgUQEzc"></param> <param name="wmode" value="transparent"></param> <embed src="http://www.youtube.com/v/Kzg_TgUQEzc" type="application/x-shockwave-flash" wmode="transparent" width="425" height="350"> </embed></object>
It's not about positions, it's about perfect sight picture. And this has been covered here. <object width="425" height="350"> <param name="movie" value="http://www.youtube.com/v/Kzg_TgUQEzc"></param> <param name="wmode" value="transparent"></param> <embed src="http://www.youtube.com/v/Kzg_TgUQEzc" type="application/x-shockwave-flash" wmode="transparent" width="425" height="350"> </embed></object>
Re: POI change with shooting positions
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Poke</div><div class="ubbcode-body">Kinda rifle are we talking about here? As asked above is your barrel free floated? </div></div> AIAW, yes the barrel is free floated. Shot from bipod without a sling. The groups were good just the POI shifted left when going from prone to the bench.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Poke</div><div class="ubbcode-body">Kinda rifle are we talking about here? As asked above is your barrel free floated? </div></div> AIAW, yes the barrel is free floated. Shot from bipod without a sling. The groups were good just the POI shifted left when going from prone to the bench.
Re: POI change with shooting positions
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: two4spooky</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Poke</div><div class="ubbcode-body">Kinda rifle are we talking about here? As asked above is your barrel free floated? </div></div> AIAW, yes the barrel is free floated. Shot from bipod without a sling. The groups were good just the POI shifted left when going from prone to the bench.</div></div>
See the video...
it's a shooter error, not the rifle. The rifle does the same thing everytime, how you shoot is what causes the impact change and having it shift laterally is definitely something you are doing.
I have several AI rifles, there is no cold bore shift, no impact shift change with position, nothing, they made to work under a variety of conditions. We just have to know how to drive them correctly.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: two4spooky</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Poke</div><div class="ubbcode-body">Kinda rifle are we talking about here? As asked above is your barrel free floated? </div></div> AIAW, yes the barrel is free floated. Shot from bipod without a sling. The groups were good just the POI shifted left when going from prone to the bench.</div></div>
See the video...
it's a shooter error, not the rifle. The rifle does the same thing everytime, how you shoot is what causes the impact change and having it shift laterally is definitely something you are doing.
I have several AI rifles, there is no cold bore shift, no impact shift change with position, nothing, they made to work under a variety of conditions. We just have to know how to drive them correctly.
Re: POI change with shooting positions
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: two4spooky</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Poke</div><div class="ubbcode-body">Kinda rifle are we talking about here? As asked above is your barrel free floated? </div></div> AIAW, yes the barrel is free floated. Shot from bipod without a sling. The groups were good just the POI shifted left when going from prone to the bench.</div></div>
See the video...
it's a shooter error, not the rifle. The rifle does the same thing everytime, how you shoot is what causes the impact change and having it shift laterally is definitely something you are doing.
I have several AI rifles, there is no cold bore shift, no impact shift change with position, nothing, they made to work under a variety of conditions. We just have to know how to drive them correctly. </div></div>
So whats the deal with the recoil pulse changeing if your point of contact with the rifle changes? The article I read said that if you shoot from a bipod at the front of the gun there is upward pressure on the stock, but if you shoot from a sling there is downward pressure. All that dosn't change the harmonics and pulse of the gun? I've never seen it on my guns but maybe the author was talking about non-floated barrels?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: two4spooky</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Poke</div><div class="ubbcode-body">Kinda rifle are we talking about here? As asked above is your barrel free floated? </div></div> AIAW, yes the barrel is free floated. Shot from bipod without a sling. The groups were good just the POI shifted left when going from prone to the bench.</div></div>
See the video...
it's a shooter error, not the rifle. The rifle does the same thing everytime, how you shoot is what causes the impact change and having it shift laterally is definitely something you are doing.
I have several AI rifles, there is no cold bore shift, no impact shift change with position, nothing, they made to work under a variety of conditions. We just have to know how to drive them correctly. </div></div>
So whats the deal with the recoil pulse changeing if your point of contact with the rifle changes? The article I read said that if you shoot from a bipod at the front of the gun there is upward pressure on the stock, but if you shoot from a sling there is downward pressure. All that dosn't change the harmonics and pulse of the gun? I've never seen it on my guns but maybe the author was talking about non-floated barrels?
Re: POI change with shooting positions
Good video, I had not seen that one before. So it is just my shooting that needs adjusting (I know I need improvement) and not my stock length. Good to know. Thank you for the help.
Good video, I had not seen that one before. So it is just my shooting that needs adjusting (I know I need improvement) and not my stock length. Good to know. Thank you for the help.
Re: POI change with shooting positions
The recoil pulse doesnt' change the way the shooter addresses the rifle does...
Barrels are free floated, how it is transferring the recoil to the barrel in a different manner, the stock is not in contact, and shouldn't be flexing in such a way to change things.
Understand why a tactical rifle is a tactical rifle... Missions change, environments they are shot change, positions the shooter uses changes, so the rifle has to stay consistent otherwise what is the point ?
When you change position, your head rotates to another position on the stock. This can cause shadowing, as well in some cases, people dont' properly adjust the parallax, which in fact turns the scope if done right into a parallax free optic like a reflex sight. With a red dot, doesn't matter where the dot is, bullet goes where the sight is pointed. They are parallax free. Where a scope with parallax that is not adjusted correctly, the the bullet will deviate from the POA because of parallax error.
Also the shooter will manage the recoil in a different manner because they are no longer in contact with ground. Watch the video, where Jacob purposely shoots it wrong, the rifle not only has parallax introduced, as well you can see him recoil in a different way because he was too light on rifle.
All this adds up to deviations..
And just because someone wrote it, doesn't mean they are right... including me.
The recoil pulse doesnt' change the way the shooter addresses the rifle does...
Barrels are free floated, how it is transferring the recoil to the barrel in a different manner, the stock is not in contact, and shouldn't be flexing in such a way to change things.
Understand why a tactical rifle is a tactical rifle... Missions change, environments they are shot change, positions the shooter uses changes, so the rifle has to stay consistent otherwise what is the point ?
When you change position, your head rotates to another position on the stock. This can cause shadowing, as well in some cases, people dont' properly adjust the parallax, which in fact turns the scope if done right into a parallax free optic like a reflex sight. With a red dot, doesn't matter where the dot is, bullet goes where the sight is pointed. They are parallax free. Where a scope with parallax that is not adjusted correctly, the the bullet will deviate from the POA because of parallax error.
Also the shooter will manage the recoil in a different manner because they are no longer in contact with ground. Watch the video, where Jacob purposely shoots it wrong, the rifle not only has parallax introduced, as well you can see him recoil in a different way because he was too light on rifle.
All this adds up to deviations..
And just because someone wrote it, doesn't mean they are right... including me.
Re: POI change with shooting positions
What about cant? I would imagine changing shooting positions would result in different cant which would affect POI. The way to eliminate cant as being a factor is to use an anti-cant device.
What about cant? I would imagine changing shooting positions would result in different cant which would affect POI. The way to eliminate cant as being a factor is to use an anti-cant device.
Re: POI change with shooting positions
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: CanPopper</div><div class="ubbcode-body">What about cant? I would imagine changing shooting positions would result in different cant which would affect POI. The way to eliminate cant as being a factor is to use an anti-cant device.</div></div>
Depends on how far away... and going from bench to prone at 100 yards, it's not a factor...
In fact I cant my ARs quite a bit and have no issue hitting a target. I use cant to get under helmets, to adjust for body armor and I haven't found it to be a problem inside 300 yards. In some situations I also cant my handgun, and that works well too..
I know cant is sexy right now, and it gives people a reason to buy something, but some times, you have to look at the shooter.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: CanPopper</div><div class="ubbcode-body">What about cant? I would imagine changing shooting positions would result in different cant which would affect POI. The way to eliminate cant as being a factor is to use an anti-cant device.</div></div>
Depends on how far away... and going from bench to prone at 100 yards, it's not a factor...
In fact I cant my ARs quite a bit and have no issue hitting a target. I use cant to get under helmets, to adjust for body armor and I haven't found it to be a problem inside 300 yards. In some situations I also cant my handgun, and that works well too..
I know cant is sexy right now, and it gives people a reason to buy something, but some times, you have to look at the shooter.
Re: POI change with shooting positions
What scope are you shooting? Does it have a parallax adjustment? I have limited experience with long range shooting, but I've found that I have to pay particular attention to my sight picture within the scope to try to be sure that I am getting square behind the scope to minimize the effects of parallax errors. Although it might sound counter-intuitive, this is why I kind of like scopes with small eye boxes. With my Nightforce 2.5-10X32, the eye box gets pretty small at 10X and it helps me to employ a consistent eye position behind the scope, inspite of shooting position.
Since I got my first "real" bolt gun, I've really taken a liking to precision shooting and what I've found has helped me the most is consistency in practice and application. I only shoot from the bench off of bags for load development and accuracy testing. All of my actual practice is done from a prone position using a bipod and squeeze bag. Of course, I'd imagine that the way I'm going it isn't really flexible, but I'm just concentrating on what I want to do with my rifle.
What scope are you shooting? Does it have a parallax adjustment? I have limited experience with long range shooting, but I've found that I have to pay particular attention to my sight picture within the scope to try to be sure that I am getting square behind the scope to minimize the effects of parallax errors. Although it might sound counter-intuitive, this is why I kind of like scopes with small eye boxes. With my Nightforce 2.5-10X32, the eye box gets pretty small at 10X and it helps me to employ a consistent eye position behind the scope, inspite of shooting position.
Since I got my first "real" bolt gun, I've really taken a liking to precision shooting and what I've found has helped me the most is consistency in practice and application. I only shoot from the bench off of bags for load development and accuracy testing. All of my actual practice is done from a prone position using a bipod and squeeze bag. Of course, I'd imagine that the way I'm going it isn't really flexible, but I'm just concentrating on what I want to do with my rifle.
Re: POI change with shooting positions
What I have personally observed over 50+ years of sighting in and shooting rifles is that the point of impact will change when you change shooting positions. Not much, but a little.
When you pull the trigger and fire the rifle, the powder lites up and builds pressure. The bullet is pushed into the rifling and starts down the barrel. As the rifleing is trying to spin the bullet to the right, the opposing force is trying to rotate the barrel to the left. In the few microseconds that the bullet travels down the bore, the rifle also moves rearward a bit. Not much, a 1/16" or an 1/8" or so, but it does move before the bullet exits the muzzle. It also wants to rotate around the center of the point opposing the recoil, which is the lug below the line of bore, so the barrel wants to move up and the butt wants to move down. As long as all this happens the same way everytime you can adjust your sight to put the bullet to the proper point of impact.
But, your own mass and inertia resist the movement of the rifle, and it does it at a different rate and at different angles when you are standing up than when you are laying down or shooting from a bench. I have never been able to sight a rifle in from the bench and have it shoot exactly to the same point of impact when shooting it offhand. It will usually print a bit higher and, for me, a bit to the left.
So, if I am going to mainly shoot a rifle from the bench or prone, I sight it in that way. My silhouette rifles which will be shot standing I sight in standing. Not saying I don't touch my offhand out on the stock against a canopy post to hold it steadier than I can hold it totally unsupported, but the recoil seems to be absorbed the same so I can sight it in.
As low-light has observed, just cause I write it don't make it so, just my humble opinions.
What I have personally observed over 50+ years of sighting in and shooting rifles is that the point of impact will change when you change shooting positions. Not much, but a little.
When you pull the trigger and fire the rifle, the powder lites up and builds pressure. The bullet is pushed into the rifling and starts down the barrel. As the rifleing is trying to spin the bullet to the right, the opposing force is trying to rotate the barrel to the left. In the few microseconds that the bullet travels down the bore, the rifle also moves rearward a bit. Not much, a 1/16" or an 1/8" or so, but it does move before the bullet exits the muzzle. It also wants to rotate around the center of the point opposing the recoil, which is the lug below the line of bore, so the barrel wants to move up and the butt wants to move down. As long as all this happens the same way everytime you can adjust your sight to put the bullet to the proper point of impact.
But, your own mass and inertia resist the movement of the rifle, and it does it at a different rate and at different angles when you are standing up than when you are laying down or shooting from a bench. I have never been able to sight a rifle in from the bench and have it shoot exactly to the same point of impact when shooting it offhand. It will usually print a bit higher and, for me, a bit to the left.
So, if I am going to mainly shoot a rifle from the bench or prone, I sight it in that way. My silhouette rifles which will be shot standing I sight in standing. Not saying I don't touch my offhand out on the stock against a canopy post to hold it steadier than I can hold it totally unsupported, but the recoil seems to be absorbed the same so I can sight it in.
As low-light has observed, just cause I write it don't make it so, just my humble opinions.
Re: POI change with shooting positions
I describe it like this:
It's the difference between driving a Porsche and driving a Peterbilt, both will get you from point A to point B, but you drive them differently.
Most people drive the rifle like a sports car, they want to minimize what they do, so while this may work in the prone, what is happening in other positions is, they are more influenced by the recoil because they don't have the stability of so much contact. With positional shooters, who see a difference, I look at one thing, where their center of gravity is. Most people, even shooting in the standing lean back, which gives the rifle a bit of a running start. Essentially they continue to drive the Porsche. When we do it, we bring the center of gravity forward, loading the rifle with our core weight which let's the rifle recoil the same.
As well understanding you're now giving that rifle a running start, the effects of a poor follow through magnifies. SO, if you are prone to "tapping" the trigger in the prone, chances are you are doing it in the other positions, thus magnifying the negative movement, and increasing the errors downrange. Many feel they need to be as light on the trigger as possible so not to influence the rifle. But positive trigger control, with a solid follow through will help keep the recoil in check.
Because the head is changing, the cheek weld changes, so you have to adjust for this, usually with Parallax. Iron sighted shooters will have a slight shift because they cannot adjust parallax out, it is easy to understand their shift. Scoped rifle shooters should not see a shift, the perspective on the reticle should not change. If it does, as in shadowing or parallax, then the shift will appear.
The rifle is a tool, it is a simple and stupid machine, it does the same thing every time -- we affect the way it acts and is what changes the position of the barrel in relationship to the target. As well if you are zeroing the system to a shooter error, again, positions will magnify this... but it doesn't mean it is right or normal.
I describe it like this:
It's the difference between driving a Porsche and driving a Peterbilt, both will get you from point A to point B, but you drive them differently.
Most people drive the rifle like a sports car, they want to minimize what they do, so while this may work in the prone, what is happening in other positions is, they are more influenced by the recoil because they don't have the stability of so much contact. With positional shooters, who see a difference, I look at one thing, where their center of gravity is. Most people, even shooting in the standing lean back, which gives the rifle a bit of a running start. Essentially they continue to drive the Porsche. When we do it, we bring the center of gravity forward, loading the rifle with our core weight which let's the rifle recoil the same.
As well understanding you're now giving that rifle a running start, the effects of a poor follow through magnifies. SO, if you are prone to "tapping" the trigger in the prone, chances are you are doing it in the other positions, thus magnifying the negative movement, and increasing the errors downrange. Many feel they need to be as light on the trigger as possible so not to influence the rifle. But positive trigger control, with a solid follow through will help keep the recoil in check.
Because the head is changing, the cheek weld changes, so you have to adjust for this, usually with Parallax. Iron sighted shooters will have a slight shift because they cannot adjust parallax out, it is easy to understand their shift. Scoped rifle shooters should not see a shift, the perspective on the reticle should not change. If it does, as in shadowing or parallax, then the shift will appear.
The rifle is a tool, it is a simple and stupid machine, it does the same thing every time -- we affect the way it acts and is what changes the position of the barrel in relationship to the target. As well if you are zeroing the system to a shooter error, again, positions will magnify this... but it doesn't mean it is right or normal.
Re: POI change with shooting positions
Tag. This can be very informative for a novice like me needing to learn a lot. Thanks guys.
Tag. This can be very informative for a novice like me needing to learn a lot. Thanks guys.
Re: POI change with shooting positions
I have never seen my zero change when I properly drive the rifle. There have been times that I have had to shoot from a pretty jacked up position. This contributed to a bad cheek weld and if my sight picture wasn't perfect, then I would see the results on target.
I have never seen my zero change when I properly drive the rifle. There have been times that I have had to shoot from a pretty jacked up position. This contributed to a bad cheek weld and if my sight picture wasn't perfect, then I would see the results on target.
