POI shifting

[Big Al]

Here are the first six shots today from a clean cold bore.

 

The rifle wasn't fully zero'd so I wasn't expecting it to be bang on, I was looking for a group and to see if the first shot was within an acceptable tolerance of the others. As you can see shots 1 & 2 were touching but then 3, 4 & 5 although good in terms of the 3/8" group size had dropped by just over an inch. Just as I was expecting the 6th shot to have settled into the lower group it then goes back up and inch to join the first two shots in what is a 1/4" group.

 

I would have been happy with either group had they been shot intentionally but instead Im a bit lost and frustrated by this unexplained POI shift. I have checked my rail and rings and everything seems fine, nothing loose, stock bolts are also good. My scope is a Vortex Viper and its the second one Ive had as the first was replaced due to POI shift, my first though is that this second scope is now playing up just as the first did?

 

Has anyone got any experience of these Vortex scopes suffering from this fault or can anyone offer an alternative theory. All shots were taken from a well rested and supported position with an 8mph zero degree tail wind. The target as you see it is canted over, that is how it was so the fact the groups are directly inline from a L to R perspective is accurate.

 

[jcampbellsmith]

Might repeating the test be a useful exercise. Regards JCS

[Offroad Gary]

I had a steyr prohunter that shot like that.

 

Could it be that your rifle is susceptible to input from the shooters hold?

[Big Al]

I had a steyr prohunter that shot like that.

 

Could it be that your rifle is susceptible to input from the shooters hold?

 

I did question my own technique Gary, I didn't feel like I did anything different between shots but can a rifle really be so hold sensitive as this?

[6.5Grendel]

My pro hunter did the same

[DaveT]

The old classic issue of a flexible forend touching the barrel?

[Big Al]

The old classic issue of a flexible forend touching the barrel?

 

No, its a solid stock with a generous barrel channel, I have at least 1mm if not more clearance everywhere and the action is bedded. Also the rifle was being rested on bags without much forward pressure.

 

Thanks for the suggestion though

 

Im going to try a different scope today if the wind allows.

[jcampbellsmith]

Two suggestions:

 

Shoot the test again yourself with exactly the same kit.

Get someone else to shoot the same test again. I'm regularly embarrassed by folk shooting my kit better than I can.

 

Regards

 

JCS

[Muskett]

Always repeat the process another day.

Check stock screws, check mount screws, check barrel channel, check breathing and anticipating the shot. Basically the whole list. Eventually it might just be the scope. I now tap the scope to ensure its moved the clicks and not stuck, even my good scopes. Check mod isn't moving and check ammunition homeload or factory. Check "loading the bipod".

 

Never bad to have someone else shoot to show its not just you; adds to the argument that something is amiss. Just doesn't take much.

 

My last rifle to do this was a Sig 522, solution was free floating the barrel as the bipod was exerting pressure on the barrel. Sent me nuts until pin pointed.

 

What rifle?

[hunter686]

Worth giving this read. I had the same thing with my .22lr until i bedded my stock.

 

http://www.rifleman.org.uk/Fuller_group_diagnosis.htm

 

Cheers

Hunter686

[tisme]

I had a rifle doing this it turned out to be a loose screw in the picatinny rail.