.270 Tikka T3 Lite Widened group at 100yds

[American Shikari]

I have Tikka T3 Lite with Millett TRS-1 4-16x50
For reloading I use Hornady GMX 130gr .270 with Hodgdon 4350 (54.3 gr)
Until last month I was shooting 100yd with 0.5" group. Suddenly My group started widening, and now I cant get it tight again

I thought I have a dirty gun so I cleaned it but still no dime

Why are my bullets flying? Brass? Scope? Scope was fine till last month. I went to range today and zeroed at 25 yards, for 50yards, iSnipe said 6.8 clicks or .68 MILs but actually I had to dial 14 clicks 1.4 MILs to get zero

Can someone help me?

 

[LoneTraveler]

Go through the gun, Check Base and ring torque. Check torque on action screws and check barrel was it same condition. (Free Float, or certain contact).
Is it a new lot of primers or new box of bullets?
Good Luck in finding the cause and cure.

 

[Hand Skills]

Do you have a different scope you can try?

I would follow Lone Traveler's advice, and mount a known working optic while I was at it.

It's easy to get overwhelmed by possible causes - more often than not, the solution is a simple one.

 

[bob4]

How wide is wider than usual ? I'd certainly follow the advice above.

 

[Hatrick]

If you were shooting 1/2" groups at 100. Why would you sight in at 25? Did the point of impact move off the target? The height of the scope can make a big difference at 25 and 50 with a tragectory like the 270.

 

[gohring3006]

What climate?
I had a load fall apart as soon as the temps dropped.

 

[xsn10s]

I'd start with Lone Travel's advise to start. Check all your screws and make sure the recoil lug is "seated" when torqueing your action screws. One possible problem is a carbon donut/ ring on the neck/ throat of the chamber. I haven't had one but I guess it's common and hard to get out of a chamber. http://forum.accurateshooter.com/threads/carbon-ring.3755192/

 

[xsn10s]

Another thing I've seen with some mono bullets and some bonded bullets is they foul easily. And they foul far quicker if they have a different jacket material in the bore prior to shooting them. My brother had a rough bore 308 win that wouldn't shoot (+2.5MOA). He had to use mono bullets so he just kept shooting it dirty then all of the sudden it started shooting tight. Then he cleaned it and he had to season the barrel with around 20-30 rounds to get it to shoot again. I'm not saying these are your solutions or even your issues. Just something to keep in mind while you troubleshoot your rifle.

 

[American Shikari]

If you were shooting 1/2" groups at 100. Why would you sight in at 25? Did the point of impact move off the target? The height of the scope can make a big difference at 25 and 50 with a tragectory like the 270.

I had to check my grouping when I missed the shot at deer at 125yd. Just to make sure I went back to the range and took a group of 3, all were 6" apart within each other. After chasing zero for a while, I thought I need to re-zero, hence the 25yds shots

 

[American Shikari]

What climate?
I had a load fall apart as soon as the temps dropped.

I didnt think of this yet but the difference in temps when it was tight vs wide is probably 10F cooler when wider

 

[gohring3006]

I didnt think of this yet but the difference in temps when it was tight vs wide is probably 10F cooler when wider

Not sure if 10 degrees would do it, I have noticed when I do a load work up in the 80s and the load fall apart when the temp is in the 30s.

 

[American Shikari]

Go through the gun, Check Base and ring torque. Check torque on action screws and check barrel was it same condition. (Free Float, or certain contact).
Is it a new lot of primers or new box of bullets?
Good Luck in finding the cause and cure.

This is a good start. I will check all the screws. I have another scope I can try. More people I talk to and more I read, I am thinking Scope is an issue. It did slip couple of time from a shooting stick in the field but I did not think much of it at the time. Nothing is rattling though

 

[American Shikari]

This is a good start. I will check all the screws. I have another scope I can try. More people I talk to and more I read, I am thinking Scope is an issue. It did slip couple of time from a shooting stick in the field but I did not think much of it at the time. Nothing is rattling though

I did discover a small wiggle at the scope base. Screws were loose. Tightened them and mounted scope. Will test at the range next week and keep you all posted. Hope that was it.

Thank you so much for your valuable input and suggestions

 

[xsn10s]

I wanted to say something but lately all that does is start arguments lol. But since you found the screws in the base were loose I suggest take them back out, clean with alcohol, and them use some blue locktite on them. I say again, blue locktite.