Tikka T3 accuracy issue

[motown]

So i have a T3 in a 7mm-08 that i recently put into a B&C medalist stock. First time out to the range is was averaging 3/4" groups with a variety of handloads. The second time out the groups opened up to 1.5-2" so at that time i figured i would have it bedded. After a local gunsmith bedded it for me i took it back out and with the same handloads i shot some groups that where under 1/2" perfect problem solved.....not so fast. Yesterday i took the rifle out again and yet again it opened up to an average of 1.5" groups.

I have checked everything as far as loose mounts which i have torqued to talleys specs and loctited. The stock is also torqued to 50 pounds as instructed by B&C. I only shoot 3 shot groups spaced apart every 3 to 4 mins and then let the rifle sit for 10-15 min as to not let it over heat. My handloads are all loaded to te same COL. The rifle is cleaned the same way after each time out and was broken in properly. I have never had a rifle that one day would shoot .5" and then the next shoot 1.5"-2" so i am stumped. Any help or recommendations would be appreciated.

 

[Lefty7mmstw]

I'm a bit surprised you are able to get over 1 moa from a tikka.
I'd dump the load and re-work it. It sounds like you are right on the edge of a stable load. I've had that a bit with lighter for caliber bullets, rather slow powder for the combination, or milder ignition. Easy to fix once all the variables come to light.
You don't say what your load is or the variables in shooting conditions.

 

[motown]

Currently my 2 best loads where 49 grains of H4350 and 44 grains of varget both with a 120 grain ballistic tip. The conditions where all about the same as far as temps in the low to mid 80's with no wind at all. I know both powders are pretty stable as far as temp sensitivity. I have been using new remington brass(will be switching to norma when its available) all trimmed and case mouths opened along with federal LR primers.

 

[Lefty7mmstw]

I'd think about going to the 140 grain bt instead of the 120. The 120 is rather light for decent uniformity. The rem brass shouldn't be an issue but norma has a good following also. Are you sure your scope is sound? Are you swapping powders mid range session? Some loads don't do well riding on another load's fouling. I just had that issue the other day with my 35 whelen; a load that is normally moa went to 2 to 3 moa because I shot a box of another load (with different powder) through it first.

 

[motown]

The scope is a new VX3 3.5-10 leupold so that doesnt concern me. I shot 3 groups with the H4350 first then went to the varget loads and got the same results out of both.

 

[Pnumatix]

I have had a simlarly frustrating issue with a Tikka T3 in 7mmRM. Ultimately traced the problem to the Talley mounts shooting loose over about ten rounds. The problem was made worse by a rearported muzzle brake and the dual pulse recoil that these things generate. Bonded and torqued them many times before giving up and going to a pinned rail. Problem solved.

 

[motown]

Bell and Carlson recommends to torque the screws to 50lbs which i did. I also glass bedded the rifle as well so should i still torque to 50 or is that maybe too much now?

 

[Pnumatix]

As I read it. You changed out the stock, rifle shot well the first outing, second time not so good. Then you had the stock bedded and rechecked the mounts (torqued etc). First time out it shot well, second time not so well.
Still sounds like the Talley's might be the source of your troubles. Retorque them again and see if the same issue presents.
As I posted above I have had this issue myself. I also went the B&C Medalist route. I even went back to the one inch Tikka supplied rings for a while and the problem went away. Tried an EGW rail. It stayed put for longer but the same issue cropped up after about ten shots. The amount of movement I was getting was tiny. I could only just feel it and it usually only became fully evedent when removing the rings for another mounting exercise. The groups just opened up with no real change in zero. I think the flat surface on the Tikka receiver which has grooves running the length of it that reduce contact area between the bases even further, make for a poor mounting arrangement. They are fine with dovetailed mounts, but struggle with any that rely on screws alone. I eventually sourced a rail from the Tikka Perforamce Centre that had a steel stud that located in the blind hole machined at the forward end of the receiver. It was an interference fit and had to be tapped in gently with a hammer. It has never given problems since (300 plus rounds).
By the way I torque all my Tikka B&C stocked rifles to 55"lbs, bedded or not.

 

[motown]

As I read it. You changed out the stock, rifle shot well the first outing, second time not so good. Then you had the stock bedded and rechecked the mounts (torqued etc). First time out it shot well, second time not so well.
Still sounds like the Talley's might be the source of your troubles. Retorque them again and see if the same issue presents.
As I posted above I have had this issue myself. I also went the B&C Medalist route. I even went back to the one inch Tikka supplied rings for a while and the problem went away. Tried an EGW rail. It stayed put for longer but the same issue cropped up after about ten shots. The amount of movement I was getting was tiny. I could only just feel it and it usually only became fully evedent when removing the rings for another mounting exercise. The groups just opened up with no real change in zero. I think the flat surface on the Tikka receiver which has grooves running the length of it that reduce contact area between the bases even further, make for a poor mounting arrangement. They are fine with dovetailed mounts, but struggle with any that rely on screws alone. I eventually sourced a rail from the Tikka Perforamce Centre that had a steel stud that located in the blind hole machined at the forward end of the receiver. It was an interference fit and had to be tapped in gently with a hammer. It has never given problems since (300 plus rounds).
By the way I torque all my Tikka B&C stocked rifles to 55"lbs, bedded or not.

Thanks for the reply. Pretty much here are my 4 trips to the range so far after the B&C stock was installed

1. Rifle shot well about 3/4" average between 4 different groups
2. Groups opened up to about 1 1/2"-2"
3. Had rifle bedded since the second trip and the groups shrank to around 1/2"
4. Groups opened back up to around 1 1/2 to 2" again.


At no point in time have i removed the scope or rings. I would agree that the mounts could be a problem if the rifle didnt shoot so well during trip #3.

 

[Mike 338]

I noticed that on the Scout model that comes with a Tikka base, they used green loctite (European version of our Red) to glue the base to the receiver. They may have a good reason for doing that.

 

[bigngreen]

I noticed that on the Scout model that comes with a Tikka base, they used green loctite (European version of our Red) to glue the base to the receiver. They may have a good reason for doing that.

Green loktite is not the same as the red, it's for close fitting parts like bearings and stuff, I use the heck out of both colors. Never though of using it on a base but that would be the kind of thing that the green would be good for.

 

[Black Sheep]

Warne makes their maxima rings in 1in and 30mm for the tikkas. They have a pin in them that fits into the hole on the top of the receiver just like the factory rings do. They also clamp onto the 'base' that is on the top of the receiver. You don't need a separate mount using these rings. I used them on my T3 in 270 WSM and I have had no issues at all.

Maxima Tikka Rings

 

[Southwind]

Warne makes their maxima rings in 1in and 30mm for the tikkas. They have a pin in them that fits into the hole on the top of the receiver just like the factory rings do. They also clamp onto the 'base' that is on the top of the receiver. You don't need a separate mount using these rings. I used them on my T3 in 270 WSM and I have had no issues at all.

Maxima Tikka Rings

I have a T3 in a Bell & Carlson in 338 win mag using the Warne direct mount rings and have not experienced any of those issues. Nothing but great accuracy.

 

[Mike 338]

Green loktite is not the same as the red, it's for close fitting parts like bearings and stuff, I use the heck out of both colors. Never though of using it on a base but that would be the kind of thing that the green would be good for.

Yeah, I didn't know how else to explain it. You'll need some high heat (torch) to separate treated parts.