Thread: Changes in the impact point

Hi all,
How much does the impact point change between different shots, eg. from the should as opposed to shooting on the bipod?
When I was at the range sighting my rifle in I used the wooden block as my rest at the front of the stock and at the butt of the stock I had another block of wood but had my hand between the wood and the stock. I didn't have my hand on the front of the stock at all, I just rested it on the wood. I now realise that this was a mistake and that having it on the wood would change the point of impact from shooting out in the bush. I'm shooting 7mm08. Do I need to worry or would the impact point change be so small that it wouldn't make a difference. I'm not shooting long range, just bush stalking and at the very most shooting at 200m for a clearing or a slip. I don't shoot with a bipod. What do you think?
Cheers

I wouldnt even bother getting hung up about your predicament. Its not going to move 6 feet like i you seem to think it will. The difference will be miniscule.

It won't be a problem Phillip.

Sorry guys but I don’t agree the change in the point of impact is not worth sorting out. Always, always, always sight your rifle in how you will be using it. I like to have absolute confidence when I have to take a 200m shot that my rifle is going to hit where I am aiming – not 4 inches out to the left and high (maybe…). Even at 200m you could be shooting in enough wind that you will want to take it into account so by not having your rifle sighted in you are simply compounding the errors.

How much the POI moves really depends on the rifle and how you sighted it in to start with. I have seen rifles that the POI shifted more than an inch at 100 yards from bipod to off the elbows and then again when shooting off the sling. I have a friend that was sighting in his rifle (Tikka T3, 260Rem) using almost the exact same technique as you describe above and he was getting groups 2-3MOA. He talked to me about it and I recommended he hold the fore end with a sandbag under his arm. He was concerned that he wouldn’t be as steady when holding the fore end but would try it as that was how he hunted with the rifle. He rang me back afterwards telling me of his now sub MOA groups…

Having the rifle out by a couple of inches at 100m might not be a problem for the ideal side on shoulder shot but what happens if, for whatever reason, you want to take a head shot? Say finishing a wounded animal that all you can see is the head?

When sighting in one of my rifles I might do accuracy testing off a bench rest but I always sight them in how they are intended to be used out hunting. If I have a bipod then I’ll sight it in off the bipod and then make sure I am still happy with it shooting prone, off my elbows with a sand bag under my arm holding the rifle fore end. If the rifle won’t be used with a bipod then I simply sight it in off my elbows using the sand bag.

How can you be sure its the stock moving shooting on/off it. it could just be the shooter when not having a decent support?

Originally Posted by Tussock

I had a plastic stocked savage 17HMR as I have said many time, with the worst tupaware stock ever made. The measured difference to POI from going from the bipod to a sandbag was 4" at 100m! I could not hit a rabbit with the thing, then I would go to the range to see what was wrong and shoot real bugholes with it. If I had 4" change with that thing, you can garuntee their are a few tupaware stocked centerfires that are similar.

Interesting, I swapped mine (22 rather than 17) to a laminate stock cos the flex annoyed me, but I never noticed a significant POI shift just better consistency with the stiffer stock. I guess flexy stock effect differs depending on harmonics etc and whether the flex creates contact with the barrel.

Agreed that its worth checking though, if it makes no difference it just makes you more confident in taking the shot so there is nothing to lose by testing except a bit of ammo.

I get what you mean about that feeling. I hate using other peoples guns and they are off and I know its not me but they give me shit anyway. But I mean getting small groups off a bi-pod and trying to get small groups without a bi-pod isn't really a fair test.

Like the guys said above, it should not be a problem.

Gillie, not sure I agree with you. I suspect you will find that POI changes in different positions is more about the person behind the rifle... Assuming that you are able to get consistent grouping from a particular position, so we can discount bedding and stock issues. You should be able to change from prone to kneeling to offhand for the same distance and windage without having to re-zero or adjust the scope in any way.

It does raise an interesting point about consistent positioning of the rifle and scope in different positions. For me it helps to have a little mental checklist to run thru before each shot:
- check the edges of the scope, some scopes go noticeably brighter the moment you are correctly aligned
- are my hands relaxed ?
- are my shoulders relaxed ?
- is my cheek / ear lobe touching the rifle stock in the normal position ?
- is my body position ok, or am I pushing/pulling the rifle in any way to get it pointed at the target ?

Theoretically, if you have good discipline and can achieve a consistent hold / cheek weld in different positions (bench, prone, offhand), you should not see a major difference. Its easy enough to test. If you are getting noticeable differences, start by double-checking your body positioning...

Haha Tussock, yup minute of deer vs internet sniping

Wouldnt bother unless your shooting longrange.. then sight in how u plan to shoot out far... a bypod or rest can lift the poi and also projuce vertical stringing with poor technique.. not by alot.. maybe an inch at 100m..

Also the possibility of poi change from a harmonic difference if ur stock isnt up to play when u use a bypod vs rest!!!

Ebf some guns just won't shoot well from a bipod with a flexi stock it's pretty simple really.
So i"m with gillie on this one bag it up if that's how you hunt

Gillie / Tussock there is no way that I wish to debate rifle accuracy with the two of you as I know less than a new born babe about the subject. That said, Phillip will be with me during the roar and there will be little chance of him shooting beyond 100 metres let alone 200 with most of the shooting opportunity likely to be in the <30 to <50 metre range hence my assurance to him that it was not going to be an issue. I have not seen Phillip shoot but let's for the sake of conducting an exercise assume that he is not good and only capable of shooting a 4 inch group at 100 metres and then lets also assume that there will be another 4 inch shift in the point of impact between how he has sighted in his rifle and how it will perform when he is shooting off hand or resting against a tree. Even under these extreme (assumed) circumstances, surely he should be capable of hitting a deer at <50 metres. My council will be for Phillip to be taking shoulder or heart/lung shots anyway as if he gets a stag he will likely want to take the trophy.

Phillip, listen to and learn from the knowledge and wisdom of these far more learned members as I am no expert on the accuracy of rifles. But my comment stands, "It won't be a problem"

I was curious about this same question, so last time at the range I did a wee test. Shooting a 25/06 Rem SPS (new-style synthetic stock, tip-bedded, so not floated at all). One shot each from:

- sitting, braced on knees/sling
- sitting at bench, holding rifle up, elbows on bench
- prone/bipod spikes in the dirt
- bench/bipod, spikes on wood

The group size for the four shots was around an inch at 100y, which suggests basically no POI shift at all. Your mileage may vary of course, but I'm now pretty happy shifting shooting setup and still trusting my zero.

Happy hunting whatever you take. Walking out of the thred now.

Originally Posted by ebf

Gillie, not sure I agree with you. I suspect you will find that POI changes in different positions is more about the person behind the rifle... Assuming that you are able to get consistent grouping from a particular position, so we can discount bedding and stock issues. You should be able to change from prone to kneeling to offhand for the same distance and windage without having to re-zero or adjust the scope in any way.

ebf, i agree with you it is always about the shooter. Particularly how they hold the rifle and as a result how it recoils while the projectile is still travelling down the barrel. I agree you should be able to change from prone, sitting (excluding the cradle), kneeling and standing wihtout changing the scope. That said most hunters hold their fore end basically the same way in these positions. But when we are talking about a "free recoiling", no resistance foreend compared to loading it up the crap off a bipod i suspect with a lot of cheaper stocks there will definately be a POI variation.