Gunsmithing Something crooked on my Rifle

[HumpHammrr]

Rifle is a new Savage M10 FCP-K in .308. I put a Weaver 20moa base on it and a Falcon 4x14 on it. (The Falcon came off a Savage M10 PC in .223 and worked perfect on this rifle.) I bore sighted it at 25 yds and again at 100 yds. I took it to the range to zero before working up a load and used all my windage to get on paper and still had to hold off to get centered. I turned the rings and checked every screw to confirm. Still off by a mile. Looking at the Brake I could not see bullet scuff but the carbon foul pattern looked odd. I took the brake off and still a mile off to the left. Just to be sure my scope was OK, I put a Night Force on it and used all of its windage.
When I call Savage for the return, what are my talking points?

 

[Avgjoe]

Savages have been known to have issues occasionally in the past with alignment of the scope base mounting holes in the action. Could possibly be your issue. Worth a close inspection.

Mike

 

[Sonic Crack]

Scope base holes or the curvature of the bore is pointed off to that side or both

 

[tony2772]

Windage adjustable rings like the USO ones would be a cheap and easy fix, maybe not the best but would work. I had this problem when I mounted a scope for a friend on his 700 LA, found the holes drilled off center on the action.

 

[Shotplacement]

Buy nicer rings, it should fix the problems

 

[xs hedspace]

But, if you boresighted it first, and it still was way off, there must be a curve to the bore. not a scope base problem. Matter of geometry....assuming you really eyeballed the bore, not used some "boresighter device". Can't picture the boresighter gadget that uses a magnet on the crown to really follow the bore at the muzzle.

 

[turbo54]

A couple things to try:

1. Swap the ring position front-->rear and rear-->front and retry
2. Try another set of rings

If no improvement from 1 and/or 2:

3: Buy a scope ring alignment set (2 precision rods with points on the end), or take to a gunsmith with them. Inspect. If they're out of alignment, contact Savage, because that shit aint right.

 

[HumpHammrr]

But, if you boresighted it first, and it still was way off, there must be a curve to the bore. not a scope base problem. Matter of geometry....assuming you really eyeballed the bore, not used some "boresighter device". Can't picture the boresighter gadget that uses a magnet on the crown to really follow the bore at the muzzle.

After mounting up the base, lapping the rings and mounting the scope, my method of bore sighting for the past 35 years has been:
1. Set the rifle up in a sandbag (front and rear) cradle so it's solid.
2. Remove the bolt and adjust the cradle so the Bullseye is concentrically centered in the bore.
3. Without movement of the rifle, look thru the scope to see where the reticle is on the paper.
4. Adjust the turrets to put the reticle on the bullseye.
5. Repeat 2, 3 & 4 as needed.

For virtually every rifle I've ever encountered, I've had success with this method. Generally putting 1st round on a 8x11 paper at 100 yds.

After seeing the comment on curved bore, I remembered an article I read somewhere (maybe Precision Shooting) about same and how the custom smith would determine bore curve and index the barrel so the curve was up or down. The big question now is, Will Savage see this as a defect covered by warranty?

Correct me if I'm wrong: Using windage adjustment rings will only correct the scope to hit at one distance. Dialing elevation (+ or -) will show left or right impact because of the curve. Correct?

PS. I've turned and swapped the rings and tried a different set of rings. Everything done still shows far left impacts.

 

[the gman]

Call Savage and send it back. You have eliminated just about everything that YOU can. It's up to them to make it right. Which I am betting they will. Let us know how your interaction with them goes.

 

[xs hedspace]

The bullet won't curve after it leaves the muzzle, so it will not change windage at different yardages, but you might see windage change, as the barrel heats up, due to stresses in the off center bore. Send it back. Is the crown looking reasonably even and square all around? Off square or damaged crown will throw the shots off bore line. Your method of bore sighting is good, but if you have a friend with a in the bore laser sighter, you might see the muzzle end of the barrel show the direction of the curve in the bore, with the laser dot not being in line with the down-the-bore eyeball spot.

 

[Gene Poole]

The bullet won't curve after it leaves the muzzle, so it will not change windage at different yardages, but you might see windage change, as the barrel heats up, due to stresses in the off center bore. Send it back. Is the crown looking reasonably even and square all around? Off square or damaged crown will throw the shots off bore line. Your method of bore sighting is good, but if you have a friend with a in the bore laser sighter, you might see the muzzle end of the barrel show the direction of the curve in the bore, with the laser dot not being in line with the down-the-bore eyeball spot.

I believe the problem with windage is when the scope axis is not parallel to the bore axis in the vertical plane--or more precisely, the effective bore axis as the bullet leaves the muzzle. If this is the case, then zeroing at one distance effectively makes a triangle where the bore axis and scope axis are two sides and the zeroing point is the tip. Extending the scope axis further causes the two axes to diverge and to hit zero at some longer distance requires adding windage adjustment--all other things being equal. Here's a quick drawing to illustrate:

 

[bodywerks]

But that doesn't explain why he was able to "bore sight" the rifle and center up the turrets visually, yet not be able to get the bullet to impact anywhere near it.
I have done several scope installs the way the OP describes, and impacts at 100 yards are usually within 4 inches, windage wise.
My first thought was the weaver base, but it doesn't explain why he still can't hit the broad side of a barn.

 

[Gene Poole]

But that doesn't explain why he was able to "bore sight" the rifle and center up the turrets visually, yet not be able to get the bullet to impact anywhere near it.
I have done several scope installs the way the OP describes, and impacts at 100 yards are usually within 4 inches, windage wise.
My first thought was the weaver base, but it doesn't explain why he still can't hit the broad side of a barn.

I'm assuming that HumpHammrr knows what he's doing with his bore sighting and is indeed correct that his impact is left of where it should be. I'm assuming that he can hit consistent zero--he just has to add more windage holdoff. If the bore is indeed curved and curvature is taken into account, the effective bore axis would be as described above. That was my point. HumpHammrr could verify this by shooting at a short and a long distance.

 

[bodywerks]

True, but you lost me at bore curvature. That's an instant cue to return the rifle to savage.

 

[HumpHammrr]

Sent the rifle back to Savage in March and got it back in April (roughly 4 weeks). On their build sheet they said the barrel was replaced. Finally got to the range today after Church and fired it. Bore sighted I was 6" left and 8" low. I turned it to the bullet hole and the next 3 shots were <.500. Needless to say I'm very happy with the Savage guys.
Now it's time to get ready for Woody's DM match.

 

[HumpHammrr]

Sent the rifle back to Savage in March and got it back in April (roughly 4 weeks). On their build sheet they said the barrel was replaced. Finally got to the range today after Church and fired it. Bore sighted I was 6" left and 8" low. I turned it to the bullet hole and the next 3 shots were <.500. Needless to say I'm very happy with the Savage guys.
Now it's time to get ready for Woody's DM match.

 

[Phezzik]

Nice. Glad to hear Savage was able to fix the issue.

 

[insight3b]

Good to hear Savage squared you away. In the future if you need a fix quick Burris Signature rings will help. I keep a set on-hand just in case:
Signature Rings - rifle scopes, handgun scopes, hunting scopes by Burris Optics

 

[aagifford]

My brother has a savage, no problems at all regarding scope alignment. Then, has 6 inches taken off the barrel and a brake installed. Also, smith found the headspace was .005" too long, and of course timed the barrel to the correct headspace, which rotated the barrel somewhat from it's factory installed position and timed the brake. Then, we went to try it out, and were about 2 feet high at 100 yards. The fix was to shim the front of the scope base up, because he ran out of travel to get a 100yd zero, couldn't get closer than 2" too high at 100yd. The bore was noted to be offcenter by the smith by .030"tir, so it was definitely a barrel curvature problem.