Thread: Point of impact trouble shooting

Looks to me that each group is not too bad taken alone, but the poi of each group is changing. Two possibilities.
1, If you have scrubbed the bore with abrasive to clear carbon and copper the barrel may take several shots to settle down.

2, the internal ajustments of some scopes can stiffen up with disuse as the lens corrections are spring
tensioned. Try winding the turrets fully
each way a few times and then back to your original zero setting, then retest for group tightness and finally for poi consistency. Good luck.

Hmmm.... what was the interval between shots, and barrel profile? I'm wondering if barrel heating over the string could have something to do with it. Also, have you fired tighter 10 shot strings before?

@Woody thanks mate will try the scope trick. I use bore tech eliminator and have used it for a while. Never had this issue but scope definitely possible as it was in the cupboard for a while!

@Bol Tackshin have fired tighter 10 shot strings for sure. Usually similar to the group in the bottom right quadrant. I don't think heat was an issue? Plenty of time between strings and ways regularly checking barrel for heat. Also live I Dunedin so it was (naturally) cold and a bit windy, which helps. That said, can always be more conscious about timing and temp next time I head out.

I had a look at the schematic for the M12 thinking maybe you'd left a detachable recoil lug out on reassembly . . . , but as far as I can see it's a fixed recoil lug, albeit quite small in area.

So another possibility is a crack or split in the stock in the area of the recoil lug or action screws.

Take the action out of stock & check there’s no shite in the recoil lug recess. When you reassemble & torque action screws check that the mag box is not trapped or binding. It should be free to move slightly. If the action is binding on mag box this will definitely cause double grouping or random poi shifts

Originally Posted by Edunn

@blip bipod with rear bag. What do you mean re barrel channel? Checked that it was free floating and clear of debris etc if that's what you mean?

Yep check its clear how flexy is the fore end as well

I've had this a couple of times in magnums.

First time it was the the recoil lug in the stock (Tikka) and it would do this based on the uneven mating and recoil action on the barrel against the lug - even though it felt like it was all in place and seated correctly. First time it was uneven lug wear - swapped to a Gunworks lug solved the issue.

Second time was a movement between the rail screws to the bases. This is about 10 years ago so please forgive me on the details I think stock the screws were M4 and came with the rail and they sat in the holes but there was movement. All most imperceptible - but you could feel it ever so slightly . We re-tapped the holes to M5 new screws with lock tight on the rail and we were good.

From there no issues. But my personal first port of call is optic - I think you need to first you need to test with a known and dependable optic you know is good. Remove that from mix and then look at these two areas.

CD

Greetings,
Two more things. Does the VX3 scope have adjustment for parallax. If not slight differences in head position may be shifting the group. I assume you are testing an 100 metres. You may want to try a test at 200 metres. Also are you shooting with your bipod on a hard surface you may want to try a bit of padding on the bench under the bipod like a bit of old sleeping mat.
GPM.

Are you using a rail with any MOA on it? If your scope is wound down too far off center of scope adjustment for a long period it can cause the springs keeping tension on the erector tube to fail eventually.

Another thing. Your aiming point may be too small and black is not ideal. You should be able to clearly see the 4 quarters of your aiming point around your cross hairs so you can make sure they are the same. At 100 metres the 50 metre NZDA targets are good, a red circle on a white background. You can clearly quarter the interior white circle. There are good reasons why these targets are used for competition,
GPM.

Thanks for all the advice and thoughts. Plenty of stuff to try when I next get a chance. Baby number two arrived during the week so will be out of action for a bit but will be sure to report back when I sort the issue out.

congrats