My latest appeal for ideas! (.22 25 yard prone *left-handed*)
Things have gone fairly well the last few weeks, and I thought I was settling down after my position re-build.
Today I shot a couple of not-great (96) practice cards, followed by an ok (97) competition card (my current goal is nothing below 97).
Then I got into position for another competition card, and found that the point of impact on the sighter had shifted into the 8-ring at North-East. I got in and out twice, still seeing the displacement, and gave up for the day without shooting the card.
This kind of large change has happened in the past, and I've never been able to work out what it is. One of my bugbears is position of the butt on the shoulder, but I tried hard to make that consistent.
What's the most likely thing that I'm changing without noticing it, anybody? Thanks for any suggestions - such a huge change that I don't understand keeps me awake at nights :)
sudden large changes in point of impact
Moderators: pilkguns, Marcus, m1963, David Levene, Spencer
Re: sudden large changes in point of impact
Hi Jedin,
For 25 yard indoor shooting, the answer is most likely in your position. Unless you had moved the sights, these should hold zero. Yes, the fit of the butt in your shoulder can absolutely have an effect; this is why so many Prone shooters in the UK use a hook butt. The hook has to be properly angled, so the butt seats fully for a natural aim, but not so far into your shoulder that your face/head pushes the rifle outwards to aim. Do I remember rightly that you have an EC stock? This will have lateral/cant adjustment built in. Use this to bring the sightline laterally to your eye when the butt is securely seated. A good tip I heard tears ago is to remove the cheekpiece so you can better feel the tension in your neck. Then adjust the cheekpiece to hold your eye behind the sights. Obviously the reach to the grip and to the handstop must be comfortable. Sling tension is vital, enough to hold everything together, but not so much your right shoulder is stressed.
How well does your jacket fit? If it's a little loose across the shoulder, the sling may be slipping, which would affect how everything fits together. In particular how/where your face furs the slanted cheekpiece you recently discussed. Is there excess material around your left shoulder that would get in the way of the buttplate. I've seen tall Free Rifle plates catch on the shoulder straps, especially on less expensive jackets; the rubber pad doesn't extend far enough back (up in Prone). Is the sling moving on your arm? I see lots of shooters paying no attention to the rotation. In my experience the will subtly alter the effective length, as well as the pressure around your arm.
However, it's not impossible the fault is with the rifle. Did you check that the sights were tight? Don't forget any raiser blocks, or an extension tube?
Also it's not unknown for some rifles to throw a few shots after a break. There's no concensus on what causes this, although a plausible explanation is the fouling cooling/drying. It might be worthwhile giving the barrel a really good clean.
For 25 yard indoor shooting, the answer is most likely in your position. Unless you had moved the sights, these should hold zero. Yes, the fit of the butt in your shoulder can absolutely have an effect; this is why so many Prone shooters in the UK use a hook butt. The hook has to be properly angled, so the butt seats fully for a natural aim, but not so far into your shoulder that your face/head pushes the rifle outwards to aim. Do I remember rightly that you have an EC stock? This will have lateral/cant adjustment built in. Use this to bring the sightline laterally to your eye when the butt is securely seated. A good tip I heard tears ago is to remove the cheekpiece so you can better feel the tension in your neck. Then adjust the cheekpiece to hold your eye behind the sights. Obviously the reach to the grip and to the handstop must be comfortable. Sling tension is vital, enough to hold everything together, but not so much your right shoulder is stressed.
How well does your jacket fit? If it's a little loose across the shoulder, the sling may be slipping, which would affect how everything fits together. In particular how/where your face furs the slanted cheekpiece you recently discussed. Is there excess material around your left shoulder that would get in the way of the buttplate. I've seen tall Free Rifle plates catch on the shoulder straps, especially on less expensive jackets; the rubber pad doesn't extend far enough back (up in Prone). Is the sling moving on your arm? I see lots of shooters paying no attention to the rotation. In my experience the will subtly alter the effective length, as well as the pressure around your arm.
However, it's not impossible the fault is with the rifle. Did you check that the sights were tight? Don't forget any raiser blocks, or an extension tube?
Also it's not unknown for some rifles to throw a few shots after a break. There's no concensus on what causes this, although a plausible explanation is the fouling cooling/drying. It might be worthwhile giving the barrel a really good clean.
Last edited by Tim S on Thu Jul 29, 2021 4:01 pm, edited 1 time in total.
Re: sudden large changes in point of impact
make sure the action screws are not contacting the action. Look at the action and see if there are any scratch marks or indentations or anything that looks like the screws could have been scraping against the action.
Last edited by 40xguy on Fri Jul 30, 2021 10:18 pm, edited 1 time in total.
Hammer to shape, file to fit, paint to match...
Re: sudden large changes in point of impact
Thanks, 40xguy - I'm pretty sure the rifle is solid. It's a floating barrel, and the clamps are firm.
Thank you, Tim, for your usual most helpful reply!
I do have quite a bit of cant, and lateral adjustment. The thing I'm less sure about is getting the butt vertically adjusted. Until recently, I mounted the butt, hoiked it up until the hook engaged, and used that as the position. But I thought that it then tended to slip down during the card. So recently I've been trying to "pre-slip" it by mounting and then letting my head weight push it to where it seems to want to be. I think I've never really understood how to use the hook properly, despite other posts on this board. Also a bit unsure about the best horizontal positioning - presuably not on the collarbone (even though there's no real recoil), but on the shoulder bone or on the muscle?
Jacket fit does seem to be a bit of an issue. It's a Kurt Thune jacket, and it's the right size for me (anything smaller wouldn't button up), but I'm slimly built for my size, and so it tends to be a little loose on the shoulders. I have the left shoulder strap as tight as it goes.
Sling rotation is something I've been trying to watch for recently, after I noticed a pulse problem coming out of nowhere! I will continue to watch for it.
Julian.
Thank you, Tim, for your usual most helpful reply!
I do have quite a bit of cant, and lateral adjustment. The thing I'm less sure about is getting the butt vertically adjusted. Until recently, I mounted the butt, hoiked it up until the hook engaged, and used that as the position. But I thought that it then tended to slip down during the card. So recently I've been trying to "pre-slip" it by mounting and then letting my head weight push it to where it seems to want to be. I think I've never really understood how to use the hook properly, despite other posts on this board. Also a bit unsure about the best horizontal positioning - presuably not on the collarbone (even though there's no real recoil), but on the shoulder bone or on the muscle?
Jacket fit does seem to be a bit of an issue. It's a Kurt Thune jacket, and it's the right size for me (anything smaller wouldn't button up), but I'm slimly built for my size, and so it tends to be a little loose on the shoulders. I have the left shoulder strap as tight as it goes.
Sling rotation is something I've been trying to watch for recently, after I noticed a pulse problem coming out of nowhere! I will continue to watch for it.
Julian.
Re: sudden large changes in point of impact
Julian,
In short, the butt should be high enough to make full contact with your shoulder when the sights are settled on the target. Using the hook to locate the plate is very common. If the plate is too high, it can stress your shoulder, or will point the muzzle too high when your shoulder is comfortable (requiring a contortion to bring the muzzle down). When it's too low the sights will stop too low, unless you drop your shoulder, which can push on the hook. It takes takes bit of trial and error, and you often need to tweak the plate to account for target height on different ranges.
If the butt is slipping, I'd look at the sling first. Often it's the length in relation to the butt length / handstop first. It's really the pull of the sling that wedges the butt against your shoulder; a well fitting buttplate helps, but won't compensate for the plate being loose against the shoulder. If the jacket is loose across your shoulders, the weight of the rifle on the sling can drag it down, loosening your position. The fit around your chest isn't so important as the fit across your back; the jacket anchors on the shooting shoulder rather than the buttons. Find videos of 2012 Olympic Champion Sergei Martynov; eight World record 600 scores with no buttons fastened!
In terms of where the plate should sit, that's more a matter of personal taste. Most Free Rifle shooters place the buttplate between their neck and deltoid, actually over the collar bone; a fixed butt like an old Martini might sit below the collar bone. Some have the butt nearer the shoulder, and others put it nearer the neck. I don't think it really matters, so long as the butt is stable, and you can reach the trigger/load easily. There is the odd shooter who has the butt on the deltoid/bicep; Sergei Martynov is a good example, although he did this because his shoulders were too oblique for a normal placement. This isn't very common, because the butt/rifle is more exposed to muscle tremor and is liable to move as you load.
In short, the butt should be high enough to make full contact with your shoulder when the sights are settled on the target. Using the hook to locate the plate is very common. If the plate is too high, it can stress your shoulder, or will point the muzzle too high when your shoulder is comfortable (requiring a contortion to bring the muzzle down). When it's too low the sights will stop too low, unless you drop your shoulder, which can push on the hook. It takes takes bit of trial and error, and you often need to tweak the plate to account for target height on different ranges.
If the butt is slipping, I'd look at the sling first. Often it's the length in relation to the butt length / handstop first. It's really the pull of the sling that wedges the butt against your shoulder; a well fitting buttplate helps, but won't compensate for the plate being loose against the shoulder. If the jacket is loose across your shoulders, the weight of the rifle on the sling can drag it down, loosening your position. The fit around your chest isn't so important as the fit across your back; the jacket anchors on the shooting shoulder rather than the buttons. Find videos of 2012 Olympic Champion Sergei Martynov; eight World record 600 scores with no buttons fastened!
In terms of where the plate should sit, that's more a matter of personal taste. Most Free Rifle shooters place the buttplate between their neck and deltoid, actually over the collar bone; a fixed butt like an old Martini might sit below the collar bone. Some have the butt nearer the shoulder, and others put it nearer the neck. I don't think it really matters, so long as the butt is stable, and you can reach the trigger/load easily. There is the odd shooter who has the butt on the deltoid/bicep; Sergei Martynov is a good example, although he did this because his shoulders were too oblique for a normal placement. This isn't very common, because the butt/rifle is more exposed to muscle tremor and is liable to move as you load.
Last edited by Tim S on Fri Oct 29, 2021 1:40 pm, edited 2 times in total.
Re: sudden large changes in point of impact
Are you shooting the card with only one "mounting" of the rifle, and loading with the rifle in place? I had a few shooters with similar change of placement of the buttplate problems, and had them remove the rifle from the shoulder to reload. They were able to build a better "memory" of the feel of the proper buttplate position by re-establishing the position every shot, and eventually go back to reloading in position and knowing when the "feel" had changed.Until recently, I mounted the butt, hoiked it up until the hook engaged, and used that as the position. But I thought that it then tended to slip down during the card.
Re: sudden large changes in point of impact
Thanks, Tim - plenty to think about next week!
Pat - yes, I mount once. I've seen in Fuller's classic book the advice to remount for every shot, but I've never seen anybody do it, so I felt shy about trying it :) But there's only me in the .22 range these days, so no call for shyness.
Pat - yes, I mount once. I've seen in Fuller's classic book the advice to remount for every shot, but I've never seen anybody do it, so I felt shy about trying it :) But there's only me in the .22 range these days, so no call for shyness.
Re: sudden large changes in point of impact
Out of curiosity, were you using the same box of ammo for both cards? Also was it old ammo?
Ammo could cause a POI shift if the speed is significantly different. I have a turner and use R50 and R100 to tune it and at the beginning the difference between the two speeds is enough to put a round into the 8 ring. From memory its the slow ammo that goes high as it leaves the barrel later and higher in the recoil. If your position had shifted too much I'd expect you to see that in the rear sight picture not being aligned. As others have said I'd recommend cleaning the barrel thoroughly with a bronze brush (and VFG paste if its old) (I clean after every shoot with bronze brush as its the only thing that will remove the carbon ring) and buy some decent quality ammo.
Ammo could cause a POI shift if the speed is significantly different. I have a turner and use R50 and R100 to tune it and at the beginning the difference between the two speeds is enough to put a round into the 8 ring. From memory its the slow ammo that goes high as it leaves the barrel later and higher in the recoil. If your position had shifted too much I'd expect you to see that in the rear sight picture not being aligned. As others have said I'd recommend cleaning the barrel thoroughly with a bronze brush (and VFG paste if its old) (I clean after every shoot with bronze brush as its the only thing that will remove the carbon ring) and buy some decent quality ammo.