Does your POI shift from different shooting positions?

Varminting and vertebrate pest control. Small game, hunting feral goats, foxes, dogs, cats, rabbits etc.

Does your POI shift from different shooting positions?

Post by Vicko » 01 Jul 2020, 5:51 pm

Honesty time!

I threw some rounds around today to get a better feel for my HMR in terms of what its doing at different ranges and positions, with different weight bullets. And to double check that putting a red light on and off a scope mounted pic rail didn't adjust anything on the weekend. I tried to replicate shooting at a fox in terms of the amount of time taken for the shots. A couple of deep breaths at most. I wasn't chasing tight groups on paper as such.

Conditions were ranging from almost still to swirly winds of around 15-20kmhr by my baldheadometer.

Found a couple of interesting things.

1. It still groups 17gr slugs tighter, but they seem to be twice as effected by wind. At 100m I was seeing groups of just over an inch using 20gr and not really seeing much more than a quarter inch drift. But the 17gr groups were half the size, about 3/4 inch higher at 100, but drifting an inch and a half! Given that where I shoot is barely still and often swirly winds I think I'll switch to 20gr from here on for foxes and leave the 17gr for paper... Incidentally my tightest group of 3 shots from the little hummer was just on .5inches. It REALLY likes them. CZ457 American with probably 100 rounds through it.

2. More importantly, I found that my POI shifts from if Im shooting prone to if I'm shooting out the window of the ute... I'm shooting just over an inch high at 100m from the ute after re-zeroing from prone today using bipods. Now.. the only other variable I can think of was that I took the bipod off. And I've only thought of that afterwards while I was scratching my head. I might head back out tomorrow and fire another group through the ute window with the bipod back on (but not in use).

Anybody else have the same result? Is it common, my poor technique or different harmonics? Parallax/focus seemed pretty good (had to be to group half an inch when I'm lifting my head up between shots surely?) What sort of variance if any do you guys notice?
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Re: Does your POI shift from different shooting positions?

Post by Blr243 » 01 Jul 2020, 6:06 pm

I would expect different poi from different rests. On the range I’m front and rear bags but in the field into the side of a dam wall I’m trying to duplicate my most likely field position so I test shoot and adjust sights while prone of a bipod .....when walkabout hunting I always shoot prone of a bipod .....but occasionally on the quadbike I take aim at a cat or fox without the legs folded down and I use horizontal rests I have built on the quadbike
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Re: Does your POI shift from different shooting positions?

Post by Oldbloke » 01 Jul 2020, 6:39 pm

Another good reason to keep to sensible distances when in the field.
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Re: Does your POI shift from different shooting positions?

Post by straightshooter » 02 Jul 2020, 7:45 am

Vicko
It's still only a low pressure rimfire so the time from firing pin fall to bullet exit from the barrel will be as much as three times as long as from a decent centerfire.
That means your hold and follow through has to be consistent for reliable field accuracy.
No less important is scope parallax and varying positioning of your eye in relation to the scope.
A 3 shot group is statistically insignificant in relation to true group center.
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Re: Does your POI shift from different shooting positions?

Post by Vicko » 02 Jul 2020, 10:38 am

I’d have thought a 3 shot group is plenty for replicating the type of shooting Im trying to replicate with this rifle. As I mentioned - I wasn’t chasing tight groups on paper I was trying see typical real world hunting variances to better understand it. By firing 3, its easier to keep the barrel cold as it would be under normal circumstances.

The grouping was obvious and consistent even at 3 shots. I shot mulptiple groups over probably an hour and a half. All were tighter, higher, and more wind effected with the smaller pill. I know already that I f I do my bit on a still day it’ll punch out groups of 5 averaging around .7-.8moa with the 17gr. I’m sure a better shooter would drop that even more, but that’s all shot from prone - all taking lots of time. Which is not what I was trying to replicate yesterday. I’m yet to come across a fox that’s happy to sit still and wait wait 30 seconds or more until I’m ready for the perfect shot :)
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Re: Does your POI shift from different shooting positions?

Post by Barnard » 02 Jul 2020, 7:28 pm

POI will shift due to different shooting positions.
how much is up to the shooter.
only way to tell for sure is to shoot different targets from different positions and take notes of your findings.
it might be as little as only 1/2 inch different at 100m,....which is nothing in the field.

one of my own findings is that different positions change the way I put my shoulder into the buttstock of the rifle, resulting in slight changes.
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Re: Does your POI shift from different shooting positions?

Post by SCJ429 » 02 Jul 2020, 8:37 pm

You may be experiencing some parallax error, good to double check this. Here is a handy guide although you probably already are familiar with the concept.

https://www.abbeysupply.com/resources/w ... e-parallax
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Re: Does your POI shift from different shooting positions?

Post by bladeracer » 02 Jul 2020, 8:46 pm

SCJ429 wrote:You may be experiencing some parallax error, good to double check this. Here is a handy guide although you probably already are familiar with the concept.

https://www.abbeysupply.com/resources/w ... e-parallax


I need to try to get some video of the worst parallax error I've ever seen.
I mounted my 3-9x40 Redfield Revolution on an air-rifle to use night vision. I wound the focus right out to get it to focus at 10m, then tried to zero it. At six-meters, moving my eye around behind the scope had the reticle floating an easy 100mm around my point of aim, totally unusable. An astonishing example of why you want to be able adjust your parallax. I believe this scope has parallax fixed at 150yds.
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Re: Does your POI shift from different shooting positions?

Post by TassieTiger » 02 Jul 2020, 9:01 pm

Fascinates me how they get around parallax issues on scopes like the z3 - a friend has a couple and you can shoot them from 10-500 yards without correction...how? Teach me ob1knob your my only hope ...
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Re: Does your POI shift from different shooting positions?

Post by Elmer » 03 Jul 2020, 2:21 pm

Vicko wrote:I’d have thought a 3 shot group is plenty for replicating the type of shooting Im trying to replicate with this rifle. As I mentioned - I wasn’t chasing tight groups on paper I was trying see typical real world hunting variances to better understand it. By firing 3, its easier to keep the barrel cold as it would be under normal circumstances.
Mate, a friend who was once ranked 3rd in Australia in benchrest said that if it wont group in
3 it sure won't in 5.

The grouping was obvious and consistent even at 3 shots. I shot mulptiple groups over probably an hour and a half. All were tighter, higher, and more wind effected with the smaller pill. I know already that I f I do my bit on a still day it’ll punch out groups of 5 averaging around .7-.8moa with the 17gr. I’m sure a better shooter would drop that even more, but that’s all shot from prone - all taking lots of time. Which is not what I was trying to replicate yesterday. I’m yet to come across a fox that’s happy to sit still and wait wait 30 seconds or more until I’m ready for the perfect shot :)
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