I recently purchased a brand new rifle from a local dealers shelf and have encountered a problem I've never experienced before. I am running out of vertical adjustment on my scope while trying to zero the rifle.

I have tried two different scopes and two sets of scope bases and keep getting the same results. Both the scopes work fine on other rifles so I know it's not a problem with the glass. I am not using high rings or any kind of see-through system. These are 40mm objective scopes mounted in medium rings with just enough clearence to keep the objective lense from touching the barrel.

I keep thinking either there's a problem with the barrel ( possibly warped?), or perhaps the reciever wasn't threaded properly and could be responsible for the barrel not be screwed on straight

Does anyone have any experience with this issue or have some ideas on what the problem might be?

most of us have seen it.. swap the rings front to back

You need to shim the back base.

quote:

Originally posted by DGR Shooter:
I recently purchased a brand new rifle from a local dealers shelf and have encountered a problem I've never experienced before. I am running out of vertical adjustment on my scope while trying to zero the rifle.

I have tried two different scopes and two sets of scope bases and keep getting the same results. Both the scopes work fine on other rifles so I know it's not a problem with the glass. I am not using high rings or any kind of see-through system. These are 40mm objective scopes mounted in medium rings with just enough clearence to keep the objective lense from touching the barrel.

I keep thinking either there's a problem with the barrel ( possibly warped?), or perhaps the reciever wasn't threaded properly and could be responsible for the barrel not be screwed on straight

Does anyone have any experience with this issue or have some ideas on what the problem might be?

What distance are you trying to zero it at? Where you have tried a couple of scopes and mounts with no change, and while you may end up having to shim the rear base, which would be a shame, there are a couple of things I would check first. I would look at the crown and the bedding.

Damaged crowns, and new guns are not exempt, can cause bullets to fly in all directions so I always look there first. Next, bedding. While it would be extremely odd that bedding would cause your bullets to fly low, I've see it in a couple of rifles over the past so I don't rule it out. There are a couple of other things I would check with regards to the alignment of the barrel and receiver axis' prior to using shims. But this is out of the scope (no pun intended) of most folks who are not equipped for it.

As mentioned, you can raise your point of impact by adding shims under the rear screw of a 1 piece base, or you can add a pressure point to the barrel at the tip of the forearm. Or, you can send it back to the manufacturer and let them solve it.

What make rifle is it?

CZ 550's had a problem with this.

Hi guys! Thanks for taking the time to respond, I really appreciate everyone's input.

The rifle in question is a Winchester M70 Classic Stainless with a Christensen Arms barrel that somehow managed to sit on a dealers shelf since about 2004. I did contact Winchester and was told that even though I purchased the rifle new, because it is a New Haven gun, the warranty is longer in effect and they basically refused to work on it.

At this point, I'm just trying to get on paper , and have been shooting at 50 yds. The barrel has a recessed crown that has no obvious or visual damage, and does not appear to be shooting erratically. It has the typical Winchester tuperware stock, so there is no real bedding to speak of.

The issue becomes apparent just trying to bore sight the rifle. Whether I remove the bolt and look down the bore or use a commercial bore sighter, the results are the same, and the groups are printing about a foot low @ 50 yds.

I bought the rifle with the intention of simply bedding it in a quality stock if it showed potential, am not opposed to rebarreling if necessary, and will try the shim on my next trip to the range. However, if there is a chance that the problem lies with the reciever, I don't want to spend a lot of time and money on a rifle that is fundamentaly flawed from the start.

I'm not really surprised hearing that. I have seen quite a few of Christensen's wrapped barrels who's bores were all over the place due primarily to the way they were turned down in preparation for wrapping. "Somehow managed to sit on the dealers shelf since about 2004". Indeed! I'd take it back to where you bought it and get my money back.

quote:

Originally posted by Jim Kobe:
You need to shim the back base.

Shim the back base as Jim said really no big deal to do so.

Can you bend the barrel back to straight with the covering Christensens puts on those barrels?

I keep shims of all sizes for this. Brownells sells them in standard sizes, they are used so much. I commonly use them for even moderate offsets so I don't lose adjusment range. This is something that seems much more prevalent than it was 30 years ago.

If the gun is shooting low, put up a target at 50 yds, use an aim point on the top edge and fire a couple of groups. If the accuracy is acceptable, don't worry about it, just center the scope, boresight and ad wedges until you are on. Then fine tune and use the rifle.

If the accuracy is not acceptable, it won't be after the shimming either, so you have more of a problem than sight-in.

I have also run into this problem on some of the newer Remington models. Have had a .338 in the XCR II that needed shims under the rear base and a .300 RUM that had the same problem. Don't know if they hand finish and take a little bit more off than they should or what.

You have a warpped or bent barrel. Not to uncommon. One possible fix is have gunsmith turn the barrel 180 degrees and re-headspace.

Do what Art S. says. Put up a aiming point so it will hit the target. Then see if it shoots good enough to please you. If it does you can shim the back base and go ahead. Or take it back and see if you can get your money back.

Some variable scopes do not have much adjustment.
Combine that with a number of possibilities and it makes for no sight in.

Lots of great info! Once again, I really appreciate everyone's help on this. Hopefully I will be able to get out to the range later this week, and I'll be sure let you guys know what happens.

From what I'm reading here, I think I would feel comfortable simply rebarreling the rifle should the current barrel not perform acceptably. Hopefully I will be pleasantly surprised, and can just put a shim under the rear base and get on with load development