Moving point of aim

[montec]

Just this week, I received my Rem 700 that used to be a VSSF, I had a new barrel
install and the action trued. After doing the break-in procedure I started to fine tune at 300 yds. The problem I am continuing to have is a shifting point of impact.
With a still wind and a cold barrel, today it shoots right on,tommorrow(same conditions)it will shoot 4 inches to right. I then move the scope to shoot on, tommorrow, shoots to the right again.I have switched out bases and rigs and scopes. I have the same scope on my 7MM Mag and it doesn't move. The scopes are Bushnell 4200 Elites 6-24. The action is glass bedded. Does anyone think that since it such a long scope on a short action that the scope may be"flopping around"

 

[BoydAllen]

Have you lapped the scope rings? Did you bed the scope base(s)?

 

[Travelor]

Sounds like a bedding problem to me. I would try different torque values on the action screws and see if that would help.

George

 

[Kenny474]

Several areas to look at: how stiff is the stock and might it be contacting the barrel due to swelling and temperature changes? Are you holding the rifle and resting it the same way? Is the case you use applying excessive pressure on the scope turrets?

The other comments are good as well.

 

[montec]

The bases and rings were Leupold STD, rings are lapped
Stock is factory, with the aluminum bedding block that comes with the VSSF-glass bedded
New barrel with only 30 shots so far, action has been trued.
I have not bedded the bases since I have not heard of this before.
As stated, the point of impact would continue moving right, yesterday, the POI started to move back to the left. I can chase the POI back and forth day in day out. but it never shoots high or low. This seemed to have started a few years ago but has been getting steadily worse. I used to be able to leave this rifle in the safe for weeks, take it out and smash pop cans at 400 yds and never have the POI shift. This problem is driving me crazy.

 

[LHSmith]

Assemble the rifle without the magazine parts, perhaps the mag box is not in proper place and you are not contacting your new bedding job 100%, also check if recoil lug recess may have something in there that shouldn't be. Was the bedding job done in conjuction with the new barrel? i.e. new bbl larger contour?
As for flopping around, BR rigs use long scopes on short actions with no problems. Bedding rings and bases is always a good idea.

 

[montec]

Before I had all this work done , the rifle was doing the same thing. As far as the bedding goes, the gunsmith and I addressed that possibility so , no, there is no bedding under the new barrel. The first thing I did was to glass bed, this shrunk the group, but the shiftting POI still remained. I had about 3000 rnds thru the barrel so I thought it needed replaced any way. The bedding has no obstructions.
I believe I must have to find a way to solidly secure the base and rings, that seems the last logical step.

 

[LHSmith]

After the bbl warms up, what is the group size? Explain in detail your bedding method and epoxy used. The aluminum bed block is notorious for being molded into the stock rather sloppily. Did you open up the stocks clearance holes?
The reason for bedding the rings is to make sure the rings are lined up properly and to ensure maximum contact between rings and scope. In some extreme cases, the mis-alignment is so bad it actually distorts the scope tube causing all kinds of internal problems. Have you used the scope you switched out ( from 7mm mag) to make sure all is back to normal on the other rifle?
I would still try it without the mag parts...it could be binding without being noticeable.

 

[montec]

After bbl warms up, the group is still under 1/4 ". I was told by a well known rifle maker just to bed right over the aluminum block, I used Brownells Acraglass. After the rifle is assembled, I then install the mag box which fits in with no effort. You may think this is crude but, I have a piece of hardened ,solid 1" round stock 4ft long that I lay inside the rings and that piece looks perfectly lined up over top over the bbl so I don't believe that when the rings are tightened that it is distorting the turrets. To answer the other question, I have re-installed the other scope back on my 7MM and there is no problem at all, it holds it's zero

 

[LHSmith]

Yes, that wooden dowel is crude...don't rely on a piece of wood to be straight enough to determine misalignment. Remove the action and look close for any shiny spots on the action where it might be rubbing...especially around the safety and the pins holding the trigger in. Make sure your stock screws have clearance around them.

 

[DCRYDER]

He didn't say "wooden dowel", he said 1" hardened round stock which is steel.

I would first replace rings with some DNZ 1-piece rings. Since they came out you will never see another set of leupolds on my guns again.

 

[tunered]

Weaver bases and 10$ tasco rings wont make one consistently shoot vert or horz the same every time, my best guess is either parralax or wind, even tho it seems calm, what caliber are we shooting????. ed

 

[montec]

shooting a 22-250-50 grn Ballistic Tips about 3725 fps
Winchester brass,36 grs Varget-CCI BR 2 primers
Bullet seated about .005 off rifling
The rifle shoots a great group but it won't shoot it inthe same spot day to day.When I did all this testing, I was shooting straight on into a very light wind, 3mph

 

[LHSmith]

Are you using flags?
Parallax...very few scopes are parallax free at the indicated yardage, and must be adjusted at the intended target each time to be 100%, also without the proper focus adjustment, you will never get a clear sight picture at the parallax free setting.
Was mirage running?
Establish a baseline....shoot only at 100yds, use same exact load, make notes on targets, wind direction, any mirage and it's direction, clean barrel, cold barrel....and be conscious of maintaining the exact same hold on the rifle for each shot......especially cheek weld.
Also, was the recoil lug ground flat?, when bedding , I'm assuming no tape was applied to the back of the lug? Is the trigger centered in the stock?

 

[LHSmith]

You may think this is crude but, I have a piece of hardened ,solid 1" round stock 4ft long that I lay inside the rings and that piece looks perfectly lined up over top over the bbl so I don't believe that when the rings are tightened that it is distorting the turrets.

If you do a search on "lapping" scope rings , you will find that many mass produced rings actually have high and low spots, and even the slightest misalignment will have you removing metal (though the lapping process) from the outside of the rings....this tells me that many scopes rings are installed crooked and the scope tube is crushed (however slightly) and there are usually lenses in this area.....so it's not just a matter of affecting the turrets. Consider also that the aluminum scope tube has an allowable tolerance for out-of- roundness, and straightness, coupled with the poor QC Remington has of late in allowing the receivers base mounting holes to be off-center, it's easy to see why lapping and bedding both rings and bases is a good idea.
Also, when using STD rings, it's never a good idea to use the scope as the "lever" when installing the front ring to the base.

 

[BoydAllen]

montec,

Regardless of make or model, good performance by one scope does not guarantee the same from a second, of the same make and model. Scope defects are more common than most shooters would believe.

The first thing that I would do, after changing to a different mount system (Can you tell that I don't like the rotary dovetail system?), bedding the base(s) and lapping, and/or bedding the rings, would be to try another scope that has performed well on another rifle. If any of your scopes have ring marks, I offer that as one proof that all is not well with the rings that it was mounted in. I have never seen a set of mounted rings that showed a perfect cut pattern when checked with a few strokes of a charged lapping bar. A very few have been close, but but none were perfect. This includes some of the best equipment that money can buy.

 

[montec]

Well Guys, changed out bases and rings again(first time since rebarreling) and it's holding. Some may strongly disagree, but I am convinced it was the rear Leupold base that was shifting. As tight as I could get it, the thing must have been shifting however minutely. It only makes sense, I would chase the POI from left to right and back again, but it never shot high or low. With all the advise about bedding rings and bases,I would have to say any moving part in the scope mounting system would have to be the flaw.

 

[montec]

BoydAllen
You are right, you cannot take for granted a brand name and assume the product is defect free. I now have an older Weaver base and ring on there. After looking thru many catalogues, many of the more expensive bases and rings are a copy of the Weaver, only difference may be better material and tighter tolerances. I lapped all my rings before I installed the scope and there are no ring marks on either scope