Tikka T3X TAC A1 suddenly shooting 6 mils low?

[GBMaryland]

Who here has experience with the Tikka T3X TAC A1?

Strange issue:

When to Frank's and Mark's PRS course in PA early in the week. (It was great and you should sign up it if you haven't taken it.)

On the second day we shot 600-1000 yards, and my 6.5CM T3X TAC shots great. No shit, it was awesome.

In the afternoon we were to shoot for correction data for our dope cards. However, I kept shooting the berm between the various 100 yard increments. (WTF?)

I can not, for the life of me, figure out what the hell is going on!

I did resight the rifle today, and found out that it is 6 mils low. ...but there is NOTHING obviously wrong with it.

Rifle configuration:

- Tikka T3X TAC A1 in 6.5CM (gotta love the man bun)
- S&B 5-25x566 PM II (backup 4-16x56 PM II UltraClear)
- EGW 20 MOA rail
- Proof CF drop in TAC A1 barrel (~220 rounds)
- Elite Iron (pic rail)
-YHM 30 cal phantom

Testing performed:

- Put on the backup scope and checked the zero. Shoots exactly like the primary - 6 mils low
- Swapped out the suppressor with it's backup, shoots in exactly the same spot
- Cleaned the carbon out of the barrel, and borescoped it - No signs of copper buildup
- Windage had not really moved
- Nothing on the rifle is obviously loose or moved

Help!

 

[clcustom1911]

Find your zero again and reset your elevation turret to 0?

Maybe someone played a trick on you and spun your turret?

There's no other explanation I can think of.

 

[GBMaryland]

Did that... and it's kinda odd. Zeros fine.

I'd agree on the turret prank, but I used the backup scope to rezero... and they've both got the same issues.

6 mils is alot.

My first thought was that I'd left to zero stop too loose, but that doesn't seem to be the case. (Given that the backup scope had the same issue, and it was locked in my trunk!

 

[clcustom1911]

Yeah man, I cant think of anything else. After you re-zero I'd probably re-check how much elevation you have left. Idk. I got nothin.

I have 2 Tikkas. One has 20moa rail, one does not. The only issue is obviously moving a scope from one to another and being off by..... roughly 6 mils.

 

[GBMaryland]

Interesting….. The scope based on the one has adjustable MOA inclination.

The rail is a 20 MOA rail.

 

[GBMaryland]

Oh yeah, I forgot… I also ran it through the lab radar in the velocity didn’t change. ~2650

 

[thexman]

If nothing changed on scope or rifle including rail. Then it most likely has something to do with the scope ring/mount.

 

[GrumpyOleFart]

☝
Your fault is transferred to your backup scope.
So must be the rig.
Let us know what it turns out to be.

 

[Old Man with Gun]

Only thing I can think of would be somewhere between the reciever and the muzzle. Any chance the barrel got hit, action moved in chasis, pressure on the barrel somewhere, change to weight of suppressor or is it now mounting differently.

If nothing changed between scope and reciever, it has to be the other side.

 

[Rthur]

Let's see a pic of the rig.

R

 

[Steel head]

It was the elite iron
Utter junk
As a kind service you can send it to me and I’ll dispose of it.

 

[GBMaryland]

I think it’s operator error.

I think that during one of the adjustment cycles I left the locking screws for the zero stop on the main scope to loose.

Later on attempting to redo my dope and check everything I tighten them just enough.

The back up scope is counter clockwise….

I took the entire thing apart.

Noticed that the butt stock on the chassis was slightly loose. Not enough for six mils but you know…

 

[GrumpyOleFart]

Combination of errors?

 

[PinesAndProjectiles]

I think it’s operator error.

I think that during one of the adjustment cycles I left the locking screws for the zero stop on the main scope to loose.

Later on attempting to redo my dope and check everything I tighten them just enough.

The back up scope is counter clockwise….

I took the entire thing apart.

Noticed that the butt stock on the chassis was slightly loose. Not enough for six mils but you know…

The butt stock isn’t goin to cause your dope to be that fucked up.

 

[GBMaryland]

That’s what I’m thinking

 

[PlinkIt]

Ok points of clarification...

You have main scope and backup scope zeroed to the rifle before the class?

When you realized the 6mil offset we were on day two, and you swapped to the backup scope and it was also about 6mil low?

You didn't swap anything else during the class correct? Bipod or rail mounting method or position?

If anything else was changed during the class I'd be tempted to swap it back to see if the 6mil repeated...

 

[GBMaryland]

Correct, only the scope we swapped out everything else was the same.

 

[PlinkIt]

 

[GBMaryland]

Turns out I had a bunch of hundred yard milling targets in the basement… So I’m going to take some of those out and check tracking

 

[GrumpyOleFart]

Interested in what the fault/faults are that caused this.
Please let us know.

 

[GrumpyOleFart]

 

[GBMaryland]

I’m still thinking operator error on my part but we’ll see

 

[OG10]

Chck your recoil lug engagement. At anytime was your B/A removed from the chassis ?

 

[GBMaryland]

Checked.

The TAC A1 is different than most rifles. It’s got a strange setup where the pic rail, receiver, and forearm get bolted together using a metal spacer. Then the forearm gets bolted to that… the barrel free floats through this setup.

 

[carbonbased]

Just making sure…did you check that the pic rail is tight? I didn't see you specifically note that you checked that (sorry if I missed it). Unless you are very unlucky, It sounds like there's something going on between the pic rail and receiver. Or your barrel is coming loose, lol.

 

[carbonbased]

Yeah man, I cant think of anything else. After you re-zero I'd probably re-check how much elevation you have left. Idk. I got nothin.

I have 2 Tikkas. One has 20moa rail, one does not. The only issue is obviously moving a scope from one to another and being off by..... roughly 6 mils.

Off chance: given what clcustom1911 mentioned, did someone at the class swap your 20 MOA rail with a 0 MOA behind your back? The old Mark I Eyeball should be able to tell you if the rail has some inclination built in.

 

[GBMaryland]

The rail seems to be on there perfectly fine.

Lab radar indicates that the velocity is exactly what it was before… So I don’t think the barrels loose or backing out.

Manage to check the primary scope today and it was 2.7 mils off… which was my dope.

it’s official I don’t know how to set turrets properly without screwing them up!

Craaaaaaaap

 

[ShtrRdy]

Is the EGW rail the "HD" model?

 

[GBMaryland]

Yes. Two pins and lots of bolts.

20 MOA. Seems to be pretty sturdy.

 

[Baron23]

Manage to check the primary scope today and it was 2.7 mils off… which was my dope.

I'm so confused (and maybe you are too! haha). I thought that the real puzzler was that with BOTH scopes you were shooting 6 mils high?

So, you rezero'd and found the S&B was 2.7 high?

After rezero'ing, its shooting to expectations?

 

[GBMaryland]

I made some quick assumptions.

The 2-25x56 PM II was 2.7 mils off. That's enough to be pretty low when shooting at distance. My assumption is that the locking screws were not tight, I moved my dope, corrected it is .1-.2 mils, and then relocked it. Something like that....

The 4-16x56 PM II I most likely turned in the wrong direction while reseting zero. That one appears to have been 6 mils off, and it was likely compounded be the fact that it turns in the opposite direction (CW as opposed to CCW of the other scope).

The primary scope does appear to track when I dial 3 mils and use the hold over in the reticle. (That's the reason I like the T3... it has the ability to hold over the horizontal line of the reticle.)

 

[Lowlight]

I do think the scope slipped some how,

It's possible... since we dialed out to 1k it could have slipped... seen it happen before especially if the zero was off

 

[GBMaryland]

Yeah, the most likely thing is Operator Error.

Heh. Given that everything else checks out, and that I had to re-zero the dials. I'm positive the in some evolution of zero resets I failed to properly torque the screws.

FWIW: I had a great conversation with the guy at Schmidt and Bender about how to re-establish mechanical zero for the turrets (which in the case of my scopes will be ~13 mils).

I was surprised... just called, got the support guy on the phone, he was more than happy to walk me through it.

(The guys from Revic were the same when I was playing with the PMR 428. Great guys also with great support. Don't like the glass as much, but the features are neat.)

 

[GBMaryland]

I think I figured it out:

What happens when m-lock screws are too long and actually press on your barrel?

Your barrel points in a different direction….

What you see here is what happens in a tikka T3 TAC A1 with a Proof carbon fiber barrel and no clearance to torque the bolts down because the bolts are too long.

Turns out that the bolts Stubbs sticking out from the mlock device push on the barrel.

What happened between rounds was that I moved the Picatinny rail closer to the action… changing how much the barrel was being pushed on, and therefore how much elevation was included in the system.

 

[PlinkIt]

That'll do it
Good find

 

[GBMaryland]

Und, now for some German engineering….

The bolts are approximately 14 mm tall as they come from RRS…

In order to have sufficient clearance of the barrel they must be trimmed to 12.27 mm tall using a grinder.

This causes them to precisely come flush with the mounting device…

Not 12.26 or 12.28… 12.27!!!



If only @Nik H were here….

 

[GBMaryland]

Of course, now I have to sight the damn thing in again….

 

[Lowlight]

Ah, a nice catch in a lot of ways and a great example of why...

The AIs Key Slots that everyone likes to compare to KeyMod are flush and countersunk so stuff like this doesn't happen.

In fact, it's why they continued to use them and modified it slightly on the AT-X.

 

[GBMaryland]

Dude, I completely forgot that during your class we moved the Picatinny rail on the front all the way to the back so I could put it on a tripod.

Imagine my horror when after I got this great idea from some guy name “Frank” to put an arca on there for using tripod, andI saw all those little devits on the bottom of my carbon fiber barrel!

It was funny because when I put the carbon fiber modified gun back together I noticed how incredibly stiff the barrel was in the action… which wasn’t the case with the original barrel and the action! “Damn, those carbon fiber barrels are super stiff! I’m impressed…”

Weeell, maybe not.

 

[Lowlight]

Ah-So, it was my fault, ... sure you can blame me for your screws hitting the barrel

All I can say is, doesn't happen with mine... maybe check yours,

 

[GBMaryland]

Certainly making me think about an AI chassis on one of my other rifles!

Truthfully, if I hadn’t gotten the tripod bug based on your examples… I would probably never have figured this out!

 

[GrumpyOleFart]

Nice to to see it sorted.Enjoy your rifle.

 

[GBMaryland]

Ah-So, it was my fault, ... sure you can blame me for your screws hitting the barrel

All I can say is, doesn't happen with mine... maybe check yours,

@lowlight …just in case: I was totally pulling your leg!

 

[Lowlight]

All good, I got it ...