Gunsmithing Problem with Tikka Build

[DeanMagnum]

I'm having a problem with a Tikka build. Specifically, it shoots great, but if I point it upright and bump the stock on the ground a few times, the gun has a dramatic (4+MOA) point of impact shift to the low left. Subsequent shots then "walk" back up the the origial POI.

My setup is as follows:
Tikka T3x rebarreled by Patriot Valley Arms in 308 with a Heavy Plama prefit barrel,
KRG Bravo stock, Vortex Razor Gen II 4.5-27 in Seekins 34mm rings, Murphy Precision 20 MOA rail

I've been trouble shooting this for a little bit, and am running out of ideas.

Here's what I've done and what I've come up with:

I put the scope and rings on a different rifle and had no problems...Not the scope and rings.

I originally had a Mountain Tactical rail that I swapped out with a Murphy Precision rail and still had the zero shift...Not the rail.

I put a different tikka (ctr) in the KRG stock, and did not have the zero shift. I also cut the top off the factory Tikka stock (t3x lite) to fit the heavy palma barreled action that's having problems, and this set up did have the zero zhift...Not the stock.

The action is sitting properly against the recoil lug. Everything is torqued to spec.

I've never put a barrel on. Is it possible the barrel is loose or not fitting properly. It's a prefit barrel with a barrel nut. It seems tight to me...??

I'd appreciate any help or suggestions you guys have. Thanks!

 

[FisherT&C]

Try backing off the barrel and resetting the head space. This time screw the barrel in till it touches the go gauge, put some loctite under the barrel nut,blue should work but if you want to use red it may take heat to get it off again, hand tighten the barrel nut against the receiver and let the loctite sit up , at least 30 minutes, then come back and torque the action on as if it's a shouldered barrel. Try 90 ft. lbs, do not exceed 100.

 

[DeanMagnum]

Thanks FisherT&C.

I should have been more clear, I had Patriot Valley Arms install the prefit barrel for me. I may end up trying to reinstall it myself using your method, but I'm thinking of sending it back to them if the barrel / barrel installation is the problem.

Is this POI shift a symptom of a loose barrel?

 

[Steel head]

Thanks FisherT&C.

I should have been more clear, I had Patriot Valley Arms install the prefit barrel for me. I may end up trying to reinstall it myself using your method, but I'm thinking of sending it back to them if the barrel / barrel installation is the problem.

Is this POI shift a symptom of a loose barrel?

I’ve shot out a few barrels with barrel nuts at 30# and never seen the issue you have.

 

[FisherT&C]

It could be a loose symptom, but the situation sounds weird frankly. I would ask PVA they may have seen something like this before.

 

[DeanMagnum]

I agree it's weird! I was hopeful somebody would have an easy fix for it.

PVA said it sounds like an optics issue, which made sense to me. I put that scope and rings on a different rifle and couldn't duplicate the problem. I bedded my Mountain Tactical rail, reversed the scope rings so they tightened from the right side, and eventually switched the rail out with a Murphy Precision rail and was able to consistently replicate the problem after each step. Which makes me think its not an optics issue. I want to exhaust every possibility before I send my action back to them.

It always goes low left then walks back up in almost a 45 degree angle back to the original POI after 3 or 4 rounds.

Anybody in the market for a barreled action that shoots 5MOA all day?

 

[jcann]

On your Bravo stock, are you sure you have the action properly torqued and the rear tang screw torqued to I believe 45 in/lbs?

 

[arob]

I would wager it’s a stock to action issue.

 

[DeanMagnum]

jcann, I'm following the instructions on the KRG stock install. I finger tight the front one, bump the buttstock on the workbench a few times to make sure the action is back against the recoil lug, torque the action screws to 65 in/lbs., then that rear tang screw to 45.

I have the same issue with this barreled installed in the factory tikka stock that I opened up the barrel channel on to free float the heavy barrel.

Really scratching my head over this one.

 

[stello1001]

I want to believe it's a mating issue. Would you mind verifying torque value on each action screw? Some thing is definitely wiggling around and maybe the action is somewhat loose in there?

 

[Tweedycarcass23jonb]

jcann, I'm following the instructions on the KRG stock install. I finger tight the front one, bump the buttstock on the workbench a few times to make sure the action is back against the recoil lug, torque the action screws to 65 in/lbs., then that rear tang screw to 45.

I have the same issue with this barreled installed in the factory tikka stock that I opened up the barrel channel on to free float the heavy barrel.

Really scratching my head over this one.

I would hold the rifle upward in the stock before inserting screws then just pushing the barreled action recoil lug down against the recoil lug slot then tighten/ torque the same inch lbs you have been . I wouldn’t bump it up and down then go to tightening it. This is Mdt’s chassis install instructions, same method I’ve always used with stocks as well. I’m wondering if bumping it a few times its actually bumping forward off the slot. Other than that maybe a Barrel torque to action issue. Good job eliminating the other possibilities first.

 

[308pirate]

Bed the action to the stock.

Both your action and your stock are mass-produced items. All mass produced items have tolerances assigned to each and every dimension and those dimensions vary within those tolerances.

Since I'm almost completely sure that KRG does not have access to Sako's engineering drawings for the T3X receiver, they had to make some dimensional and tolerancing assumptions when they designed their inlet for same. There's nothing wrong with that, it's just the way it is with aftermarket products when their makers don't have access to the engineering data from the OEM.

Most of the time things work really well and the stock and action are a happy mate. Your set of action and stock seem to be one of those instances where dimensions add up to a loose fit. Bedding will fix that.

Please don't try to tell me "but chassis don't need bedding". That's internet bullshit. The reality is that most don't seem to need it but some clearly do.

 

[stello1001]

Bed the action to the stock.

Both your action and your stock are mass-produced items. All mass produced items have tolerances assigned to each and every dimension and those dimensions vary within those tolerances.

Since I'm almost completely sure that KRG does not have access to Sako's engineering drawings for the T3X receiver, they had to make some dimensional and tolerancing assumptions when they designed their inlet for same. There's nothing wrong with that, it's just the way it is with aftermarket products when their makers don't have access to the engineering data from the OEM.

Most of the time things work really well and the stock and action are a happy mate. Your set of action and stock seem to be one of those instances where dimensions add up to a loose fit. Bedding will fix that.

Please don't try to tell me "but chassis don't need bedding". That's internet bullshit. The reality is that most don't seem to need it but some clearly do.

Pretty much along the lines of what I was thinking.
It really does seem like a mating issue and bedding will take care of it...

 

[dustingaunder]

Try lowering the torque on the action screws. I usually go to 55# on the KRG stuff and it shoots great. It suggests trying lower torque in the manual for better accuracy.

 

[jcann]

Your problem is unique. It doesn't sound like a barrel issue but stranger things have happen I guess. The fact that this is happening in two different stocks makes it more of a challenge.

If you can pull the recoil lug out of the Bravo chassis check to see if the mating surfaces of the lug to action seem okay.

If everything seems okay, attach the recoil lug to the action via lock tight and after it sets-up replace both action/lug back into the chassis. After this, torque action screws properly (without seating action into stock by way of beating it on the workbench). If it doesn't fix it, at least you eliminated another possibility.

Is there a chance the barrel nut is contacting anything after you bump the stock a few times?

 

[308pirate]

Try lowering the torque on the action screws. I usually go to 55# on the KRG stuff and it shoots great. It suggests trying lower torque in the manual for better accuracy.

A POI shift following a slight impact is not going to be helped by lowering the action screw clamping force.

He needs to bed it making sure everything that should clear the chassis is clear of the chassis

 

[dustingaunder]

A POI shift following a slight impact is not going to be helped by lowering the action screw clamping force.

He needs to bed it making sure everything that should clear the chassis is clear of the chassis

You don’t know that and it’s easy to try.

 

[Precision Underground]

Anybody in the market for a barreled action that shoots 5MOA all day?

What’s the price on it? I enjoy a good challenge!

 

[308pirate]

You don’t know that and it’s easy to try.

LOL two mating parts move in relation to one another but the answer is to make the connection looser.......

Ya buddy whatever you say

 

[308pirate]

Anybody in the market for a barreled action that shoots 5MOA all day?

I'll buy the entire rifle minus scope for $100

 

[BCX]

We going open bid on this?? $150 just send the action lol.

 

[Steel head]

$151.99

 

[Jrb572]

Does the KRG stock come with a new recoil lug? If not did you forget to transfer it over.

 

[Mordamer]

Switch to a different scope on the same gun. Switching the same scope over to a different rifle isn't the same thing. I agree with Patriot valley arms, it sounds like an optic issue.

To all the people saying it is a issue with the action to stock fit. I bet $1 you can take a zeroed rifle out of a stock and set the barrel directly on a bag with the bag just in front of the action and fire the barreled action with no stock at all and you won't even have 4 MOA of zero shift. Something else is going on.

Also, Vortex has great customer service. Take that scope off and send it to them. They'll be able to tell if it has issues.

 

[Mordamer]

One other thing, I'd like to raise the bid to $400.

 

[DeanMagnum]

Thanks for all the input.

The action screws are torqued to spec, unless my Wheeler FAT wrench is off. I have tried running them looser ( until the group size opened up to the point where I couldn't tell if it was happening or not) and it didn't fix the problem.

I have tried holding the action against the recoil lug and tightening the screws without bumping the stock. Same problem happens.

The barrel nut is not touching any part of the stock.

jcann, I will try and lock tight the recoil lug from the Bravo to the action and see how it goes. The Bravo did come with a recoil lug installed.

I will glass bed the factory stock and try that.

My first thought was a receiver/chassis mating issue too, but after I had the exact same problem happen in both stocks it got me thinking it's not. Also my CTR shoots great in the Bravo, so if that is the problem it's the receiver not the stock. What's the chance Tikka goofed up the machining of the receiver? It looks the exact same as the CTR as best I can tell.

I threw on the only other optic I have, a 1-6x and it was still having the problem. I attached a picture of a 3 round "group." First two same hole. Bumped the gun around, shot the third round and it's low left. This is at 25 yards.

 

[Precision Underground]

Thanks for all the input.

The action screws are torqued to spec, unless my Wheeler FAT wrench is off. I have tried running them looser ( until the group size opened up to the point where I couldn't tell if it was happening or not) and it didn't fix the problem.

I have tried holding the action against the recoil lug and tightening the screws without bumping the stock. Same problem happens.

The barrel nut is not touching any part of the stock.

jcann, I will try and lock tight the recoil lug from the Bravo to the action and see how it goes. The Bravo did come with a recoil lug installed.

I will glass bed the factory stock and try that.

My first thought was a receiver/chassis mating issue too, but after I had the exact same problem happen in both stocks it got me thinking it's not. Also my CTR shoots great in the Bravo, so if that is the problem it's the receiver not the stock. What's the chance Tikka goofed up the machining of the receiver? It looks the exact same as the CTR as best I can tell.

I threw on the only other optic I have, a 1-6x and it was still having the problem. I attached a picture of a 3 round "group." First two same hole. Bumped the gun around, shot the third round and it's low left. This is at 25 yards. View attachment 7365523

Did you do this a couple of times or just once? When chasing your tail you have to make sure to be thorough. I’d want to see this same thing happen at least 3 times in a row before eliminating the scope. Not sure if you tried a different scope base when you did this but I would def suggest that. I think the stock is fine since it does it with the factory stock too.

 

[DeanMagnum]

I did it a few times, but only took a picture of one group. I usually shoot 15-20 rounds after each change. The problem has been consistent.

When trying the different scope, I did use a different scope mount as well (an Aero SPR one piece mount). No improvement.

Have a good Fourth!

 

[BCX]

My guess its a recoil lug fitment issue.

 

[Precision Underground]

I did it a few times, but only took a picture of one group. I usually shoot 15-20 rounds after each change. The problem has been consistent.

When trying the different scope, I did use a different scope mount as well (an Aero SPR one piece mount). No improvement.

Have a good Fourth!

What about scope base?

 

[supercorndogs]

Switch to a different scope on the same gun. Switching the same scope over to a different rifle isn't the same thing. I agree with Patriot valley arms, it sounds like an optic issue.

To all the people saying it is a issue with the action to stock fit. I bet $1 you can take a zeroed rifle out of a stock and set the barrel directly on a bag with the bag just in front of the action and fire the barreled action with no stock at all and you won't even have 4 MOA of zero shift. Something else is going on.

Also, Vortex has great customer service. Take that scope off and send it to them. They'll be able to tell if it has issues.

This, 5 MOA something is bad wrong. Has the O.P contacted PVA?

 

[DeanMagnum]

For scope bases: I originally had a Mountain Tactical 20 MOA rail. I contacted them and explained my issue. They were awesome and they sent me a new rail no questions asked. The new rail did not fix the problem, so I bedded the original rail. That didn't do it either, so I thought maybe the MT rails are not to true 1913 spec and Seekins rings don't work with the MT rails. I got a Murphy Precision 20 MOA rail, and that didn't fix it either.

 

[DeanMagnum]

This, 5 MOA something is bad wrong. Has the O.P contacted PVA?

I'm with ya!

I contacted PVA, and they thought it sounded like an optics issue. I'm trying to rule everything out before I have to send it back to PVA.