Scopes?

[Sloter]

Okay I’m hoping there’s a simple answer to this, a friend of mine and I often go shooting together (shotguns) but we’ve recently started shooting a rimfire his not mine, but when we use his gun I can’t hit a bloody thing. I use my air rifle and am fine and other people I’ve leant it to are fine with it but if I lend it to him he can’t hit a thing! How can this be? Surely whatever is in the scope is what you’ll hit if the scope is correct, how can a gun be accurate for one person and not another?

And before anyone asks neither of us are cross-eyed!

[libs]

Not sure of the technicalities, but I have had a simular experience when using a remmy 700 in .308 over 100 yards. The bloke I was with put 3 shots in an inch or there abouts 2" above the bull.

 

I put 3 shots in about 1.5"ish but about 6 low and 3 left. This was off a bench with a bipod.

 

Maybe there is something to it??

[casts_by_fly]

A bench with a bipod can cause problems because the gun will typically bounce around on the bipod when you shoot. Depending whether you are pushing into the bipod or holding neutrally and whether you are pulling into your shoulder or shooting more 'free' will change the POI wuite considerably. If the gun has a cheaper synthetic stock with a bunch of flex in it (the Remmy 700 SPS is known for it) then it will be all the more pronounced. On a solid bench, you're better off with a good set of sand bags or bags on a rest.

 

In the first case, a cheaper scope that has a lot of parallax can cause different POI for different people. If the scope has a bunch of parallax, then even the same person will have shifting POI depending on the cheek weld on the stock and head position. Two people are unlikely to have the same of both. Additionally, the bipod info above holds here.

 

Thanks

Rick

[libs]

A bench with a bipod can cause problems because the gun will typically bounce around on the bipod when you shoot.

 

If I got a pattern rather than a group I could understand this, but a 'bounce' would be far more likely to cause a random error surely? And as this was my second ever centerfire encounter I was please with a group anywhere, and this was with the synth stock and a swarovski optic scope so I'm not sure the quality of the glass would have ,ade an impact.. Could it be purely down to where I shoved my face on the stock??

[wannabefisher]

In this scenario POI is to do with where/how you hold the gun, and your grouping is related to your consistency in holding it that way. Therefore two people can hold it in different ways and get the same grouping but in a different place on the target

[casts_by_fly]

If it is a remmy SPS, then I would say it was forend flex when used with the bipod. One person pushing in versus one person neutral or pulling back will cause a big difference, but both will be able to shoot groups as long as their own hold was consistent.

 

Thanks,

Rick

[The Burpster]

In this scenario POI is to do with where/how you hold the gun, and your grouping is related to your consistency in holding it that way. Therefore two people can hold it in different ways and get the same grouping but in a different place on the target

 

 

+1......

 

due to the way 'scope works, it will be at zero for the person that sets it. You only need your eye to be 1/4' in a different place for the POI to move significantly.

 

One person using a rifle all the time wil have a 'feel' for where they rest their cheek on the stock, they will replicate that alomst instinctively every time they use it. Even if you copy that postition exactly unless your face has exactly the same diemensions (highly improbable) then the POI will shift. You can illustarte this on your own rifle. Set the rifle up whilst prone (or bench rest it) and rest the butt on a bean bag so it is steady. set the x-hairs on a target bull as you would normally. Now leaving the rifle in the same position roll your face to right away from the stock but keep focusing on the reticle, you will now see them move in relation to the target, although of course the rifle hasnt.

 

I have a big face, and I struggle when shooting others rifles.

[casts_by_fly]

burpster,

 

That is true for scopes with parallax problems. If the parallax is dialed out then you won't have that problem.

 

thanks

Rick

[PAULT]

sounds like mount trouble to me

[Milligan]

burpster,

 

That is true for scopes with parallax problems. If the parallax is dialed out then you won't have that problem.

 

thanks

Rick

 

I'd agree with you there. If the parallax is set correctly the crosshairs shouldn't move when you move your head. If it's a fixed PA scope then it will be set for a certain distance, typically 100yds but this may vary, and you will have varying degrees of error at different ranges. So, a different head position will move the POI.

 

Grip could account for some of the difference but if you are both grouping I'd put my money on parallax. The only other thing I can think of is one of you is canting the rifle, which if done consistently would also move the poi.

 

Hope it helps.

 

Will :(

Edited May 20, 2009 by Milligan

[Devilishdave]

I shoot with 3 mates and we have all used the same rifle from time to time and we are all within 1/2 an inch of eachother at 100m and all shooting 1MOA ish. To be honest from group to group I can move 1/2 MOA just my self because of slightly diffferent position. IT is all about consistency and repeatability.

 

Dave