17hmr POI change 50-100 yards


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made2cut
May 2, 2012, 03:34 PM
My 12 yr old son and I were having small caliber fun last Saturday. The Savage 93R17 was dead on at 50 yards but when we took it out to 100 the POI changed dramatically high and to the left. The only change was increasing the magnification from around 5 to 9x. Could this have caused the change? We ran out of time otherwise I would have cranked the scope back to 5x to see if it went back to center. No real wind to speak of but it was blowing left to right when it did. It wasn't the shooter cause my boy's hits were the same (he started compensating trying to hit the 10 ring).

:confused:

Kurt

http://i122.photobucket.com/albums/o278/made2cut/Spring12/1022_917_Targets.jpg
http://i122.photobucket.com/albums/o278/made2cut/savage93.jpg

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rcmodel
May 2, 2012, 03:52 PM
Bullets don't climb like airplanes so?
Your 50 yard zero should put your group about 1/4" lower at 100 yards.

Has to be shooter aiming point error (subconsciously holding over at longer range?)
Or scope error from changing the power setting.

Was I you?
I would test the scope at 50 yards by shooting a 5 or 10-shot group and changing the power from high to low one shot, then low to high the next shot.

It shouldn't change the group location, so if it does and you end up with two groups in different locations, the scope is defective.

rc

chrome_austex
May 2, 2012, 04:00 PM
Assuming you didn't change positions in a way that would cause bipod bounce? (like switching from a soft surface to a hard surface), didn't switch ammo, and didn't assume a different shooter position. The only other thing I can think of aside from RC's scope error, would be that something came loose (scope mount or action screw?)

Check the magnification like rc suggests. Its a good candidate.

Scimmia
May 2, 2012, 04:07 PM
Bullets don't climb like airplanes so?
Your 50 yard zero should put your group about 1/4" lower at 100 yards.

Na, 17 HRM could easily still be climbing at that point. Guessing that the sight plane is 2.5" above the bore axis, a 50 yard zero should put the group about 0.7" higher at 100 yards using Winchester's balistic calculator.

Of course, .7" is nowhere near the 4" change you're seeing. Definitly check the scope as rc suggested.

rcmodel
May 2, 2012, 04:10 PM
The scope on the rifle in the picture is not 2 1/2" above the bore.

I agree if it was, the bullet would still be on an upward trajectory at 100 yards and would hit less then an inch higher then it did at 50 yards.

But the scope in the picture is not high enough to cause that.

rc

made2cut
May 2, 2012, 04:52 PM
Arrg... that would suck if it was the scope but I can't think of anything else. It's a Nikon Buckmaster, certainly not top of the line but should be plenty good enough on a 17hmr. I guess another trip to the range is in order, which does not suck :D.

BTW - that is not the bipod we were using pictured. We were using a 6in on a bench, same ammo throughout the session.

Thanks for the replies!
Kurt

rcmodel
May 2, 2012, 05:00 PM
I suppose it could also be scope parallax, but that much error is a lot.

You have a centerfire scope with the parallax set error free at probably 150 yards.

At closer range and at high power setting, if you move your eyeball around behind the scope, the cross-hairs will move on the target.

See this about that:
http://www.6mmbr.com/parallax.html

True Rimfire scopes have the parralax set error free at about 60-75 yards.

rc

RedHeadHunter
May 2, 2012, 06:04 PM
I have had more than one rifle that would have the point of impact rise, usually high and left, when the barrel heated up. 4 inches is a lot, but it is worth a shot.

TurtlePhish
May 2, 2012, 06:18 PM
I have had more than one rifle that would have the point of impact rise, usually high and left, when the barrel heated up. 4 inches is a lot, but it is worth a shot.


.17HMR doesn't really heat up all that much. I have the same rifle in a Monte Carlo stock, and I can put a box of 50 rounds through it in about 5 minutes and still be able to touch the barrel. Granted, it IS a little toasty, but touchable. POI doesn't change, either. 100yd groups just open up maybe 0.5".

LJ-MosinFreak-Buck
May 2, 2012, 08:38 PM
I've read on here before that changing the power settings can alter it a little bit, that's why I set my variable at 10x, and sighted it in at that power setting.

rcmodel
May 2, 2012, 08:46 PM
I kind of disagree.
Years ago when variable scopes were in their infancy?
Yes that was true!

I had Weaver V-8's back in the 60's that would change a bunch depending on the power setting.

Today, if you have a reasonable to good quality variable that won't hold zero with power changes, there is something bad wrong with it.

rc

ole farmerbuck
May 2, 2012, 08:59 PM
I dont know but it looks like the scope is touching the barrel.

LJ-MosinFreak-Buck
May 2, 2012, 09:47 PM
rcmodel:

I hear you there, I'm not sure if mine is capable of holding zero through changes, will have to try it. I just read about it, set it to 10x, and went from there.

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