Weird diagonal grouping. Reduced loads. Tikka 300wsm

[Jimbee]

I decided to play with some reduced loads. Tikka 300wsm, 2- 5 shot groups with 175TMK, 35 grains and 40 grains H4895. SWFA 3-9, 11 twist factory barrel cut to 20", threaded, 9inch TB. Scope is in Sportsmatch rings, of course, and torqued, loctite used. Action screws torqued to 65lbs, loctite used. I'm fairly certain that the grouping progressed from top down and right to left. After 6 shots, alternating from top square (40 grains) to bottom square (35 grains), I figured the reduced loads were garbage. I almost left the range but decided to shoot the remaining 4 I had loaded. I waited 2 minutes between shots on the first 6 shots. I sharpied the first 6 shots, returned to the bench and shot the remaining 4 at their respective targets without waiting between shots. The pattern appeared to continue. Any ideas? Hopefully tomorrow I will have time to shoot some different loads or factory ammo to compare.

 

[Jimbee]

 

[Macintosh]

Seems unlikely for 2 diff loads to do that together, even if they are similar. Guessing it has to be a scope/rifle issue.
If you have factory bottom metal then 65in/lb is almost 50% higher than tikkas max recommended torque for action screws. I know people do it, but I have also heard of people having problems as a result. If the bearing surface caved-in I guess the gun could be moving in the stock? Any indication of movement innthe barrel channel or behind the action?

 

[Dexter Grayson]

I’m gonna agree that it’s the scope. My tikka .300wsm did crazy horizontal groups, ended up being the internals of my Zeiss scope.

 

[SDHNTR]

And you weren’t dialing between shots?

 

[Jimbee]

Seems unlikely for 2 diff loads to do that together, even if they are similar. Guessing it has to be a scope/rifle issue.
If you have factory bottom metal then 65in/lb is almost 50% higher than tikkas max recommended torque for action screws. I know people do it, but I have also heard of people having problems as a result. If the bearing surface caved-in I guess the gun could be moving in the stock? Any indication of movement innthe barrel channel or behind the action?

There's no evidence of movement and I did a bed job with aluminum pillars and some devcon.

 

[Jimbee]

And you weren’t dialing between shots?

No dialing

 

[SDHNTR]

100 yds? That’s super weird.

Tear everything down and start over.

 

[Jimbee]

100 yds? That’s super weird.

Tear everything down and start over.

I'm going to swap the scope and see what happens.

 

[KenLee]

If you have another decent scope that will just drop into the same rings, I'd swap out and shoot a group using the different scope.
If that doesn't work, I'd do as SCHNTR suggested and tear everything down...and go 40-45 pounds torque on the base screws.

 

[Jimbee]

If you have another decent scope that will just drop into the same rings, I'd swap out and shoot a group using the different scope.
If that doesn't work, I'd do as SCHNTR suggested and tear everything down...and go 40-45 pounds torque on the base screws.

I accidentally ordered an extra 3-9 SWFA when they were in stock.

 

[KenLee]

I accidentally ordered an extra 3-9 SWFA when they were in stock.

Nice!

 

[SouthPaw]

Any chance the muzzle device is loose?

 

[Jimbee]

Any chance the muzzle device is loose?

I checked. 'Twas tight

 

[Jimbee]

Mounted new swfa. Only removed top of scope rings and torqued to 22lbs. I didn't clean the old loctite or put any more on yet. Shot 10, 1 shot, moved scope up, 2nd shot, moved scope up and right. Shot 8 more. Same diagonal pattern, just not as spread out and this time it seemed to go up and right. Bedding issue? Going to look into that next when I have time.

 

[KenLee]

Has it shot full power loads well with the same setup?

 

[Jimbee]

Has it shot full power loads well with the same setup?

Yes. Going to shoot some factory Norma ammo if the bedding doesn't look janky, (which I don't expect it to).

 

[KenLee]

Yes. Going to shoot some factory Norma ammo if the bedding doesn't look janky, (which I don't expect it to).

If it still shoots the full power loads good, I'd ditch the 300wsm weak load idea and dig a 308 out of the back of a safe

 

[HandgunHTR]

Probably not related at all, but why did you loctite your action screws?

Just a quick PSA to everyone reading. If you properly degrease and torque your screws, be it rails, rings, or action, there is no need to use loctite.

As to your issue, I am going to say it is most likely your bipod. Are you loading it up the same way every time?
Take it off and shoot off of a good bag (front and back) and report back.

 

[Wrench]

I agree that you need to look at your form.