POI shift between bench and prone (another stupid question)

[LC 6.5 Shooter]

I was at the range Sunday getting some practice shooting prone. I was shooting 300 yds which is 1.1mil elevation. Shooting from bemch POA and POI where the same. Shooting prone at 5 yds closer with no change in conditions ammo etc resulted in a consistent 1.5-2” higher POI vs POA. I thought I had seen a gunwerks video that showed some change shooting prone vs bench but would you expect that much. I had been possibly having parallax issues would you think that would be more of the cause.

 

[VP47PPC]

I would work on the theory that I was supporting the rifle differently between bench and prone and see if it duplicated consistently and what if any change in form you want to undertake. I notice this more with a 9 pound sporter in say 06 or 270 when i use a rifle rest and rear bag VS hand hold rifle with just a day pack as a front rest. I use the rest & bags to verify accuracy and sight in hand held resting on day pack.

 

[j-huskey]

Lots of information around poi shifts in the following links. Somewhere @Lowlight discusses it, as being rifle fit, head placement, and recoil management. I think it's in the first link below.

https://www.snipershide.com/shooting/threads/question-on-prone-shooting-position.129/

https://www.snipershide.com/shootin...2-shots-of-perfect-recoil-management.6892389/

https://www.snipershide.com/shootin...fting-straight-up-under-recoil-today.6878589/

 

[ShtrRdy]

That sounds like a parallax problem.

Shooting prone generally ends up 1/2moa lower than when shooting from a bench.

 

[Milo 2.5]

If it was a 5 yard difference in distance, same target, I would not look at parallax. Most people tend to free recoil more when shooting off a bench, then go prone and load the bipod up, creating impact changes. I think you did the opposite, where your prone was too comfy for a bipod load.
You said you were getting some prone practice, which I assume is newer to you(?), I'd go back and try it again, focusing on recoil management when prone. I think you created your own situation, and it is an easy fix.
EDIT: Usually free recoil results in about a half moa rise, that would be 1 1/2" at 300 yards.

 

[Precision Underground]

That sounds like a parallax problem.

Shooting prone generally ends up 1/2moa lower than when shooting from a bench.

I think that’s assuming the only difference is speed due to more or less weight snugged to the rifle. POI could easily be higher from something the shooter is doing differently when prone vs bench. Too much downward cheek pressure + relaxing the grip on the rear bag could def do it.

 

[LC 6.5 Shooter]

If it was a 5 yard difference in distance, same target, I would not look at parallax. Most people tend to free recoil more when shooting off a bench, then go prone and load the bipod up, creating impact changes. I think you did the opposite, where your prone was too comfy for a bipod load.
You said you were getting some prone practice, which I assume is newer to you(?), I'd go back and try it again, focusing on recoil management when prone. I think you created your own situation, and it is an easy fix.
EDIT: Usually free recoil results in about a half moa rise, that would be 1 1/2" at 300 yards.

On the bench I was shooting bipod and doing like Franks video and load into the bipod with shoulders in front of knees. Yes newer to prone but I was trying to apply the fundamentals Ive been learning through the SH online training etc. I was also loading the bipod when shooting prone and dont believe I was free recoiling it. I was engaged with the rifle pulling it straight back into shoulder pocket. I am going to a training class with Aaron Roberts soon but was trying to get as much practice as possible before hand. Ill reshoot it this weekend and see what happens.

 

[Milo 2.5]

On the bench I was shooting bipod and doing like Franks video and load into the bipod with shoulders in front of knees. Yes newer to prone but I was trying to apply the fundamentals Ive been learning through the SH online training etc. I was also loading the bipod when shooting prone and dont believe I was free recoiling it. I was engaged with the rifle pulling it straight back into shoulder pocket. I am going to a training class with Aaron Roberts soon but was trying to get as much practice as possible before hand. Ill reshoot it this weekend and see what happens.

I believe you, lol. I just think sometimes when we switch positions, the gun can be in such a comfy position that we forget fundamentals. If you get the same results, try a higher bipod height which forces you to load it correctly. At 300 yards,it would take a lot of velocity diff to equal an inch and a half. Even free recoil to supported yields little in velocity changes.

 

[Rocketvapor]

What bullet/ammo/velocity?
Half of your shift was likely due to trajectory (0.7")
Check a calculator for 295yds and 300yds.
That leaves about an inch difference between bench and prone.
An INCH at 300 yds.

Did your shoulder and cheek contact the rifle the same in both positions?
i.e. body angle?

 

[LC 6.5 Shooter]

What bullet/ammo/velocity?
Half of your shift was likely due to trajectory (0.7")
Check a calculator for 295yds and 300yds.
That leaves about an inch difference between bench and prone.
An INCH at 300 yds.

Did your shoulder and cheek contact the rifle the same in both positions?
i.e. body angle?

147eld. Lapua 4xf. CCI450. H4350 41.9g. 2725 f/s.

I feel like I shoulder and cheek contact was same (probably some difference). Ised the same bipod for both and same rear bag for both.

 

[Jack Master]

Frank did a video on this. His change of impact was less than yours. You might have other factors going on unless you drastically change the recoil management.

 

[Rocketvapor]

When shooting prone body angle, straight back vs canted to your weak side changes the recoil impulse and the POI.
When shooting from a bench unless you drape yourself over the rear of the bench, you will likely be at a different angle.

Next time out try prone dead straight back from the bore, to a slight angle toward your weak side, exposing more 'shoulder' to the stock.
Fine tune your position.

OK, watched the nice video. Thanks Frank.
The first part of the video was at what range?
So, 15 to 20 fps difference, the OP also had a 5 yd difference (300 vs 295).
Plug that into your calculator.


Want to see Zero shift caused by recoil management?
Try prone vs offhand with a baby sized cartridge like a 5.56
Measure yours, remember it, and apply it.

 

[Jack Master]

Here is another video Frank and Jacob did back in 2010 about POI shift from positional changes. Read the description below the video.

 

[LC 6.5 Shooter]

Here is another video Frank and Jacob did back in 2010 about POI shift from positional changes. Read the description below the video.

So in a nutshell something changed in ME when going prone. Or could be the parallax issue I was having.

 

[Rocketvapor]

If you noticed a parallax problem (like shadowing) from one position to the next, yes, Zero point will change.
This shows up @ 100 yards which I assume was the distance shot in the two previously referenced training videos.
A quarter inch shift from sitting at the bench to prone would be about 3/4 inch @ 300
So, To the op.
A 5 yd change in distance, I assume having to go prone out in front of the bench, Closer =higher hit.
A velocity change from recoil management, 15 to 20fps with a similar cartridge. Faster=higher hit.
A parallax shift in zero due to less than perfect position behind the scope and scope adjustments,

and your POI vs POA went UP 1/2 MOA (1.5"@300yds) from the bench to prone?

What were the group sizes and number of shots you used to evaluate this?
What scope power were you using @ 300 yards?

Looks like 14X in the video posted above.

 

[LC 6.5 Shooter]

If you noticed a parallax problem (like shadowing) from one position to the next, yes, Zero point will change.
This shows up @ 100 yards which I assume was the distance shot in the two previously referenced training videos.
A quarter inch shift from sitting at the bench to prone would be about 3/4 inch @ 300
So, To the op.
A 5 yd change in distance, I assume having to go prone out in front of the bench, Closer =higher hit.
A velocity change from recoil management, 15 to 20fps with a similar cartridge. Faster=higher hit.
A parallax shift in zero due to less than perfect position behind the scope and scope adjustments,

and your POI vs POA went UP 1/2 MOA (1.5"@300yds) from the bench to prone?

What were the group sizes and number of shots you used to evaluate this?

4 groups. 2-4 shot groups and 2-3 shot groups. All 4 groups were a little better than half moa to half moa.

 

[Rocketvapor]

OK, sounds like enough to evaluate a shift.
Thanks.

Unless you can really stabilize at the bench (per the video) work on the prone position with results being your baseline.
Then put in your logbook, seated at the bench---- Zero= +1/2MOA (come up to zero)


I find I need a slightly different cheek weld (or scope height) and LOP sitting at the bench vs prone.
I can fidget and squirm and get either to work but my comfortable setup is different for the 2 positions.

 

[LC 6.5 Shooter]

OK, sounds like enough to evaluate a shift.
Thanks.

Unless you can really stabilize at the bench (per the video) work on the prone position with results being your baseline.
Then put in your logbook, seated at the bench---- Zero= +1/2MOA (come up to zero)


I find I need a slightly different cheek weld (or scope height) and LOP sitting at the bench vs prone.
I can fidget and squirm and get either to work but my comfortable setup is different for the 2 positions.

Agreed setup needs to change between the two for sure. I noticed eye relief etc is slightly different between positions. Definitely going to make prone my baseline.

 

[Jack Master]

So in a nutshell something changed in ME when going prone. Or could be the parallax issue I was having.

Yes, I think the first place to look is in you. ( I mean this nicely) The rifle is a machine and does not change when position is changed. We as the shooter have/are changed. Keeping good fundamentals when changing positions limits and amount of change in the POI. Site picture is often over looked, or quickly breezed through as checked box. Taking the time to make sure your head placement is right when changing positions is key, watching for shadowing and parallax adjustment. Going from the bench to prone can, for some people, cause an uncomfortable neck tension if the position is not built to fit you. (eye relief, Bipod height, lop) This uncomfortably can make us overlook the site picture issue because to fix it we need to strain our necks more. This is the reason a rifle and scope placement are set for the shooter in the prone position. (plus its most stable) In other positions we can, generally, adjust our body mechanics easier to keep good site picture and manage recoil.


Rocketvapor summarized this well above. I agree with this.

A velocity change from recoil management, 15 to 20fps with a similar cartridge. Faster=higher hit.
A parallax shift in zero due to less than perfect position behind the scope and scope adjustments,

and your POI vs POA went UP 1/2 MOA (1.5"@300yds) from the bench to prone?

 

[LC 6.5 Shooter]

Yes, I think the first place to look is in you. ( I mean this nicely) The rifle is a machine and does not change when position is changed. We as the shooter have/are changed. Keeping good fundamentals when changing positions limits and amount of change in the POI. Site picture is often over looked, or quickly breezed through as checked box. Taking the time to make sure your head placement is right when changing positions is key, watching for shadowing and parallax adjustment. Going from the bench to prone can, for some people, cause an uncomfortable neck tension if the position is not built to fit you. (eye relief, Bipod height, lop) This uncomfortably can make us overlook the site picture issue because to fix it we need to strain our necks more. This is the reason a rifle and scope placement are set for the shooter in the prone position. (plus its most stable) In other positions we can, generally, adjust our body mechanics easier to keep good site picture and manage recoil.


Rocketvapor summarized this well above. I agree with this.

No worries definitely just constructive criticism. Those who cant take it never learn and that is my intent so thank you. All makes perfect sense. When I first started shooting seriously (within the last 1.5years) I pretty much just shot off the bench at 100 yds. Then got more interested in long range precision shooting and here we are. So I think I will tweak rifle setup to prone and like you said adjust to everything else. I know there are tons of thoughts on LOP but how do you personally set LOP for the prone. MPA chassis so pretty adjustable. Thanks for all the help btw

 

[Jack Master]

I adjust my length of pull by 2 factors. (this is my way, others may say different and you'll have to find what works for you)

1. Head placement on the cheek rest. I want to place my head near the center of the rest. This is a position I can index each time I mount the rifle. This can be indexed from any position. With a good cheek weld and good recoil mitigation you can spot your shots much easier. Having the cheek rest at the correct height for the optic is critical while doing this. Sometimes you'll need to take a photo of this position to fully understand where you head is at on the cheek piece.
2. Angle of the trigger hand while holding the rifle and squeezing the trigger. Too tight of a wrist angle can make shooting uncomfortable and reduce the 90 degree finger trigger control. If I can not hold a prone position for a good while without resting the wrist I am in a bad position. This factor is different for each person depending on how they hold the rifle. Some don't hold the grip much, others apply pressure to the rear which changes the wrist angle as well. Fundamental Frank will want reward pressure applied equal to about the weight of the rifle.

You'll have to to work with 1 and 2 to find the sweet spot. If 1 is just right but 2 is too close you may have to sacrifice on 1 a bit to get 2 to work as well. Its not worth pulling the trigger if you can't pull it correctly.

Items to note:

• I like to place the optic on the rifle to find the correct cheek rest height, then remove the optic and work on 1 and 2. After the LOP is set, mount your scope to fit your eye relief needed on max power. Make sure your don't have to 'rubber neck' forward to get the perfect site picture.
• Shoulder pocket placement is critical during this setup. You have to know where you are going to put the rife every time. Have a look at this thread for more on that topic--> Shoulder Pocket (watch Phil's other facebook videos and you'll see how he holds the rifle with his trigger hand as well, its a bit different than Frank)
• While setting this up clothing is a factor to think about as well. Summertime is T-shirts and wintertime is a thick coat. I set mine up in a T-shirt for summer shooting, when I do most of my shooting. If I am shooting a lot in the winter I might reduce my length or remove a spacer (during the winter only) to account for the thicker clothing.

After you have gone through all of this, you'll likely change or slightly adjust things the next couple times your shoot. Frank's analogy is: you have to adjust your car mirrors and seats the first couple of time too. Its a process to get it just right. I find dry fire can help with the initial adjustment, after that its fine tuning while shooting.

Best of luck