Huge poi shift and bore sight oddity

[Grizz1148]

So I'll try to explain as short as possible, buddy just bought a Christensen Mesa 338. He shot a few groups not so hot but breaking in the rifle as Christensen states. I go there today and he says shoot it, so I did. Peterson brass, rel 33, Berger 300 otm, misses 100 yd target completely to the right twice. Dial it over and can't tell where it's going. Loaded some more, here's where it gets weird. Bore sighted as I do with every gun every time with no issues. Look through bore and align bullseye with scope. Usually always within a few inches of center and never off paper, until now, at 50 yds. Over 12 inches left. Now to center it we had to max out windage in the scope and found that the 40 min NF rail was too much for the scope and didn't allow for enough horizontal travel. Tried another scope to be sure it wasn't just the scope. Replaced with 20 min rail and was able to move over enough to sight in. Same thing bore sight looked good, shot way left. We then sighted in at 100 and shot 3 shot group, not great but consistent. Decided to load a few Barnes lrxs 265, same powder, case, primer, brass, poi shifts over 10 inches right at 100 yds. Dumbfounded by this we fired another Berger to be sure scope didn't shift and it had not, that bulletin fired back in the group of bergers. Any ideas?

 

[david g ranes]

Pull your rail put a streight edge on the screw holes see of they line up over the bore or are they bored crooked. David

 

[WildRose]

At first blush I'm thinking busted scope.

 

[Joefrazell]

Sounds like a fun issue to me. That poi shift from bullet to bullet is pretty extreme. I'd contact Christensen and have them look at it. 338 ammo is expensive.

 

[TheBoctor]

Sounds like the OTM's aren't agreeing with something. Maybe there's some wonkiness in the crown? Might not be enough twist and it's sailing that far? Could try some 300 SMK's to see if it's something specific to the bullet profile.

 

[LDHunter]

I have read and reread your paragraph and I'm not sure what you're asking.

Are you saying that both scopes had the same problem? If so the likelihood that the scope is the problem is very slim but if I were you I'd optically center both scopes and then one at a time mount on the 20MOA rail and then shoot a 3 shot group at 25 yards. Use a big piece of paper so you're definitely on target. If your groups are more than 1/2" at 25 yards with the scopes optically centered so they're definitely operating in the center of their adjustment range even with factory loads then just pack the rifle up and send back to Christensen Arms.

If groups are reasonable with both scopes but still waaaaay off center and the rail for sure a good rail such as a Nightforce or equivalent then send it back to Christensen Arms.

Your discussion of loads and where they shot made no sense to me so I can't comment on that but in a custom rifle there's no way properly constructed loads should make a huge difference at 100 yards.

You might want to rewrite your discussion of what all you've done so far to clarify and I know you were likely very frustrated when you wrote it.

I know you have a lot of faith in your bore sighter but shooting is always way more reliable than any bore sighter and I suggest you remove the possibility of your bore sighter being off for some reason.

The likelihood of the problem being anything but something being wrong with the rifle that causes the erratic results you've been getting is pretty slim but return to basics. Have you checked to make sure the action screws are tight? Does the fired brass look normal? Don't even bother worrying about the crown causing this much trouble.

 

[Grizz1148]

I have read and reread your paragraph and I'm not sure what you're asking.

Are you saying that both scopes had the same problem? If so the likelihood that the scope is the problem is very slim but if I were you I'd optically center both scopes and then one at a time mount on the 20MOA rail and then shoot a 3 shot group at 25 yards. Use a big piece of paper so you're definitely on target. If your groups are more than 1/2" at 25 yards with the scopes optically centered so they're definitely operating in the center of their adjustment range even with factory loads then just pack the rifle up and send back to Christensen Arms.

If groups are reasonable with both scopes but still waaaaay off center and the rail for sure a good rail such as a Nightforce or equivalent then send it back to Christensen Arms.

Your discussion of loads and where they shot made no sense to me so I can't comment on that but in a custom rifle there's no way properly constructed loads should make a huge difference at 100 yards.

You might want to rewrite your discussion of what all you've done so far to clarify and I know you were likely very frustrated when you wrote it.

I know you have a lot of faith in your bore sighter but shooting is always way more reliable than any bore sighter and I suggest you remove the possibility of your bore sighter being off for some reason.

The likelihood of the problem being anything but something being wrong with the rifle that causes the erratic results you've been getting is pretty slim but return to basics. Have you checked to make sure the action screws are tight? Does the fired brass look normal? Don't even bother worrying about the crown causing this much trouble.

10 inches of poi shift?

 

[Grizz1148]

Pull your rail put a streight edge on the screw holes see of they line up over the bore or are they bored crooked. David

Did that. Holes appear straight

 

[Grizz1148]

Sounds like the OTM's aren't agreeing with something. Maybe there's some wonkiness in the crown? Might not be enough twist and it's sailing that far? Could try some 300 SMK's to see if it's something specific to the bullet profile.

Twist rate is good. Just odd there's a 10 inch poi shift and not that the two have anything to do with each other but the bore sighted barrel clearly pointing off target has me stumped.

 

[Grizz1148]

At first blush I'm thinking busted scope.

Thought so too at first, that's why we tried 2 scopes as mentioned in my OP.

 

[John Polk]

Have you retorqued all the fasteners?

 

[codyadams]

Likely issue is because you are trying to shoot the rifle in a liberal state!!!! Just kidding, I know not all of New York is, well, New York.

First thing I would do is get some Burris Signature XTR rings, optically center your scope (maybe 15-20 MOA down from optical center to accommodate your rail) and then use the ring shims to bore sight/get on paper at 100 yards, then you just have to take the scope a few MOA away from center. That will sort out one issue, and make it easier to get a full, paralax free view through the scope at all magnifications, and will also make it better on the internals of the scope, not being maxed out in one way or another. This seems like the biggest issue in my mind currently.

The Berger loads, are they ones loaded for that rifle or are they just ones that you had for another rifle? If the bullet has a longer OAL than the throat of that rifle allows, and they are being jammed, that can sometimes cause somewhat more significant POI shifts, in my experience.

I have had rifles that when I bore site as you state, they are barely on paper @100, they are still usually within 8-10" at 100 though. Bottom line, I would just get those rings, then see if it is going to shoot accurate. If it is going to shoot well, don't worry if it shifts 10" or more from one load to another, the simple solution to that is, don't switch loads. I'm still not sure WHY it would act like that, shifts of 1-4" are pretty standard, 10" is a lot, but if the rifle is performing......I wouldn't worry about it honestly.

If you get those rings and get the scope issue sorted, and it simply won't shoot good with factory loads that CA recommends or any of your handloads, that is when I would contact CA customer service.

 

[Grizz1148]

Have you retorqued all the fasteners?

One of the very first things

 

[Grizz1148]

Likely issue is because you are trying to shoot the rifle in a liberal state!!!! Just kidding, I know not all of New York is, well, New York.

First thing I would do is get some Burris Signature XTR rings, optically center your scope (maybe 15-20 MOA down from optical center to accommodate your rail) and then use the ring shims to bore sight/get on paper at 100 yards, then you just have to take the scope a few MOA away from center. That will sort out one issue, and make it easier to get a full, paralax free view through the scope at all magnifications, and will also make it better on the internals of the scope, not being maxed out in one way or another. This seems like the biggest issue in my mind currently.

The Berger loads, are they ones loaded for that rifle or are they just ones that you had for another rifle? If the bullet has a longer OAL than the throat of that rifle allows, and they are being jammed, that can sometimes cause somewhat more significant POI shifts, in my experience.

I have had rifles that when I bore site as you state, they are barely on paper @100, they are still usually within 8-10" at 100 though. Bottom line, I would just get those rings, then see if it is going to shoot accurate. If it is going to shoot well, don't worry if it shifts 10" or more from one load to another, the simple solution to that is, don't switch loads. I'm still not sure WHY it would act like that, shifts of 1-4" are pretty standard, 10" is a lot, but if the rifle is performing......I wouldn't worry about it honestly.

If you get those rings and get the scope issue sorted, and it simply won't shoot good with factory loads that CA recommends or any of your handloads, that is when I would contact CA customer service.

Loads were built for this gun. Gun is new. Thanks for the reply