My Group Moved - Help

2 weeks ago I mounted a new Tract Toric 4-20x50 MOA scope on my rifle. I sighted it in at 200 yards and set the zero stop there, I fired 20 rounds during that session. This weekend I shot a 5 round group at 200 yds and it was still on, then I dialed up 8.25 MOA and fired a 5 shot group at 500 yards and elevation was good. I shot a 15 rounds at steel then dialed it back down to 200 yards (zero stop) and fired my last 2 rounds and this time my 200 yard group was 3.25 inches low.

I checked the scope base and rings and they are tight. The base is a EWG 20 MOA and rings are Burris Signature Zee.

I checked the stock fit and its tight, the barrel is still free floated. The Stock is a Boyd At-One that has pillars installed and bedded.

This afternoon I'm going to secure the rifle in a vise a dial the scope up and down a few times to see if I see anymore issues returning to zero.

Is there anything else I need to do before I return the scope to Tract?

Did you let the rifle barrel cool between groups? What gun and what profile barrel? Assuming that the POI is not due to barrel heating, the scope would be my first suspect.

Yes, slow fire, barrel remained cool. Gun is a Stevens 200 (Savage 110), Caliber 6.5x55, barrel is X-caliber light varmint 8" twist. Its a consistent sub .5 MOA gun at 200 yds and sub .75 MOA at 500 yds due to my poor eyesight and shooting skills.

Did you go to the zero stop or go to the stop and then to your zero setting? Zero stops are to keep you from going to far, not meant to be a dead on zero

My zero stop is set to 200 yard zero. After shooting at 500 yards I dialed elevation back down to 200 yard zero where it was stopped by the zero stop. My group was 3.5" lower than where it should have been.

Other than worry about the scope being a problem, I’d re-zero and try again, to see if the problem exists or repeats.

^This. If the load is a half moa load, you should return to zero every time. If not, the first thing I'd check is the scope. Otherwise, something else is moving and causing the POI to shift. What it is, no clue. But scope tracking would be looked into. Next would be the rifle and making sure something didn't come loose or moving around.

Yep, shoot a box test with it. I bet you'll find it's the scope. But I agree with earl39, I would not put the zero-stop exactly at your zero.

Well I put the rifle in a vice and dialed to max elevation and max windage several times and it returned to zero each time. Guess I'll shoot it some more before deciding if I need to send the scope back or not. Hope it doesn't let me down at an inopportune time.

Thanks for the advice guys.

Why not put the zero stop on zero?

Fireman explained it to me the last time I was at his range and we were zeroing a couple of my guns. Perhaps you use a different load that requires you to come down a bit or maybe you share your scope and mount between different guns that have different zeros, you can't do that if your zero stop is set at 0 if you need to drop down from there. Also, the zero stop is predominately to keep someone from going too far when they are having to dial down several rotations. If you have to dial down thru several revolutions the stop will quickly let you know where your zero is when adjusting back down, you just will have to make the small adjustment to get you to your zero.

Earl

Thanks Earl that makes sense.

It's called down travel. I can set my ATACR to have a hard stop at "0". But I dont, I leave about .5 Mil past "0". So when I love the scope to another rifle, I don't have to address the zero stop, if I have to bring the rifle/scope zero below "0".

But do a tracking test on your scope anyway. Something still seems fishy.

Be sure to remove parallax. It can cause a shift in poi.

Nice gun. I hope turns out to be a zero stop or operator issue and not an actual tracking issue. Keep us posted.

Thanks again for all the good advice. Since dialing the turrets while the rifle was in a vice didn't show any problems, I'll try to get out and shoot a box test this weekend.

Ditto on the tracking test. I'm not super familiar with the Tract Torics, but if you ruled everything else out, something scope related maybe it, and simply running it out to max adjustment and back won't necessarily show you a tracking issue. You need to dial with something to actually compare the reticle movement to.