prone vs parallax question

[rockwind]

curious about something.

i understand parallax and how it works (for the most part). as long as you get the 2 "focal planes" lined up, when you move your eye, the reticle should not move in relation to your target.

however, i recently read an article about how when you change from bench shooting to prone shooting, your eye is in a different position on your stock and thus, you shoot lower.

i thought the whole point of adjusting parallax was to fix this. however, i saw another video where (gunwerks) where someone went from bench to prone and the gun shot lower, so it appears to be true.

i am sure i really should just say to myself "that is just the way it is, get used to it"
however, if someone knew exactly why it is, it would be good to know.

 

[FearNoWind]

I personally don't subscribe to the theory that shooting lower from the prone position than from a bench is attributable to anything more than differences in equipment. For a certainty, it has nothing to do with how your eye meets the cross hair/target image through the scope. I'd be more likely to consider a theory that considers how the rear bag/shoulder position affects the rifle's behavior on the bench compared to the prone position. Frankly, I don't shoot any lower in prone than I do from the bench and I don't personally know any accomplished shooter that does.
When you watch video demonstrations, look closely at the body position of the prone shooter. A lot of them are not lined up behind the rifle; they're at an acute angle to the line of the barrel. That's not correct. You'll also find that some prone to bench comparisons use a rest on the bench and a bipod in prone. That's comparing apples with oranges.

 

[HARPERC]

If we're talking bench to bipod the POI changes I see most often have to do with the surface the bipod is on.

If we're talking bench to prone with a sling, a variety of things may be introduced, such as barrel to stock contact, and the muzzle rise being limited.

 

[royinidaho]

I shoot from pedestal rest on bench, bipod on bench (though the bipod sits on thin sand bag - but very solid) and prone w/pedestal rest and bipod in the dirt (no pad/cloth/etc between feet and dirt) and POA = POI in all cases.

Just say'n.

 

[rockwind]

well, i was only asking cause i watched this



and read this

Fitting The Long Range Rifle


seemed like 2 fairly good sources, but got me confused, especially about parallax and prone. i personally have not done enough shooting yet to notice but thought others may have. i plan on shooting prone in the field so i figured i would start shooting prone all the time to get used to it.

would still like some other opinions.

 

[WildRose]

I personally don't subscribe to the theory that shooting lower from the prone position than from a bench is attributable to anything more than differences in equipment. For a certainty, it has nothing to do with how your eye meets the cross hair/target image through the scope. I'd be more likely to consider a theory that considers how the rear bag/shoulder position affects the rifle's behavior on the bench compared to the prone position. Frankly, I don't shoot any lower in prone than I do from the bench and I don't personally know any accomplished shooter that does.
When you watch video demonstrations, look closely at the body position of the prone shooter. A lot of them are not lined up behind the rifle; they're at an acute angle to the line of the barrel. That's not correct. You'll also find that some prone to bench comparisons use a rest on the bench and a bipod in prone. That's comparing apples with oranges.

This.

If you are not driving the rifle the same from each position it will affect your POI. Get a consistent mount and the problem is solved.

 

[Greyfox]

This.

If you are not driving the rifle the same from each position it will affect your POI. Get a consistent mount and the problem is solved.

+1. Skip states in the video that he is trying to simulate the free recoil set-up that he has on the bench when converting to prone. I have also seen POI shifts when you do this. The effect that has to be controlled is the barrels movement for the first 1/8-1/4" before the bullet leaves the barrel. When hunting, where shooting positions can vary greatly, just knowing the effect from bench to prone and adjusting for POI changes for these two positions is not enough for how I hunt. I found it to be useful to use rifle management techniques that keep the barrel orientation upon firing constant regardless of shooting position. I find this much harder to do when shooting free recoil, or light hold. I use a hard hold to get consistent POI. IMO

 

[FearNoWind]

well, i was only asking cause i watched this

(Video)

and read this

Fitting The Long Range Rifle

would still like some other opinions.

I'm pleased that you posted your question. I already offered a point of view relative to the video so I'll leave that one alone.
The article emphasizes proper "fit" of the rifle to the shooter. If the "fit" is consistent and the support (bipod, rest, etc.) remains the same then there should be no change in printing on target. There is always the possibility, of course, that a difference in the surface upon which the bipod/rest is situated could affect how the recoil is managed as it travels back through the stock; but that has nothing to do with sighting. Trouble with a lot of articles that compare prone to bench is, IMO, that they forget to include data about the type of rest employed in each instance.
IMO, the article's focus on proper fit is perhaps the most critical point offered. I do not, however, see any reason for the cheek weld to differ from bench to prone. Once you've mastered "fit" you'll know instantly when you're out of position and you should be able to close your eyes, establish a cheek weld, and open your eyes to find the cross hairs centered in the scope. A bad fit just doesn't feel right and you'll find yourself fighting the rifle for alignment with the target. Again, the key to accuracy is consistency in every element encountered.

 

[FatBoy...]

Most of my long range rifles are NRA High power prone rifles. I get my zeros and do load testing from a bench and then do my final zero and final groups from the sling and coat. I attribute the POI change to the difference in tension/pressure on the stock and how that effects recoil. It has nothing to do with parallax, I don't change it at all when testing at a specific yard line.

 

[WildRose]

+1. Skip states in the video that he is trying to simulate the free recoil set-up that he has on the bench when converting to prone. I have also seen POI shifts when you do this. The effect that has to be controlled is the barrels movement for the first 1/8-1/4" before the bullet leaves the barrel. When hunting, where shooting positions can vary greatly, just knowing the effect from bench to prone and adjusting for POI changes for these two positions is not enough for how I hunt. I found it to be useful to use rifle management techniques that keep the barrel orientation upon firing constant regardless of shooting position. I find this much harder to do when shooting free recoil, or light hold. I use a hard hold to get consistent POI. IMO

Yep. Just keep the rifle recoiling in the same plane and same axis every time no matter what position you are in and the POI will remain pretty constant.

Of course, that's a whole lot easier said than done.

 

[HARPERC]

I like the way you said that. Conceptually tweaked things a bit for me.