Wondering Zero

  • Excuse the long post but I feel I should explain everything as best I can.

    I have a kahles 5-25 that up this point I’ve had zero trouble out of. I recently had a barrel go south on me just before a match. I borrowed a friends rifle for the match and put my kahles on it. Everything was going good and at the end of day one I was one point behind the leader. Towards the end of day two I started dropping shots I shouldn’t be dropping and on the last stage of the match I dropped 4 shots at 325 yards by shooting over top of the target this cost me a top 10 finish. Fast forward a few days I now have my new barrel and start the break in process. After some stabilization rounds I zeroed the gun and went to the range to get the barrel settled down. Everything was going good but towards the end of the day I started missing targets again. I rechecked the zero and was .4 low and .2 left so I just figured the zero had moved while the barrel was settling in so I made the adjustments and went home. I went to the range today and confirmed zero and it was .4 high so I adjusted it and went on about my business. After a few rounds I started missing low again so I check zero and was .3 low. This time I removed the gun from the chassis and re torqued everything including the rings and re zeroed the rifle. 30 or 40 rounds later I started missing small targets again off the top so checked zero and was .1 high. After adjusting the zero for the 3rd time today it stayed put for the rest of the day.

    The thing that has me puzzled is it’s only the zero that’s shifting, the tracking is spot on every time. So part of me feels like it’s a scope issue and the other part feels like it’s something else.

  • You would know 1000 times more than I would what your normal experience is ... but when I have such an issue, I assume it is me. And I go back to the idea we've discussed before ... "You are never done zeroing yourself" ...
    So is it remotely possible your position is changing, even just a tiny bit ??
    For me, that's what I would suspect.
    Other possibility is parallax. But by now I've memorized my 100yd parallax settings on all my scopes (whether they be at 75 yds on the scope ... or 150 yds on the scope :D )
    Per your words, this is a new mating of the scope to the rifle ... so perhaps the eye relief is not perfect ??

  • @bull81

    1. Missing high with your friends rifle at the end of the day.

    This could easily be fatigue. Shooters tend not to build rear support as they should when they are fatigued, because they don't build it properly normally. Shooters tend to use more muscle force than they should, which results in lack of repeatability under fatigue.

    1. The zero wandering high and low.

    Great deal of variables here. New barrel can be 100% the cause of this. Some barrels can take a couple hundred rounds before they settle in... if they ever do. Not every barrel is good.

    Could be 100% the fault of the kahles scope as well. Wouldn't be the first one I've heard of not holding zero. I can sell you a Tangent Theta, and you can mount it up and see if it persists. You can mount the kahles up on a different rifle you know to be shooting properly and test it. You could swap barrels and try a different one.

    Really not much option here other than swapping hardware until you narrow down the problem. If you swap around a bunch of hardware and still can't narrow it down... it's probably you.

  • Thanks for the reply’s fellas. I think I found the issue, the last barrel in this mini chassis was a heavy Palma this one is a MTU and it’s hitting hard on the bottom of the barrel channel. I didn’t notice it until now because it has about 1/8 of an inch of clearance on the sides. I’m about to open it up and will report back.

  • @bull81 That would do it.

  • Opened the barrel channel up and rezeroed the rifle. Doubt it’s a coincidence but it was exactly .4 mils low. I went home for lunch and dialed up 14 mils and then back down to zero and fired one round. Looks like the problem is solved