Analyze my target - is something wrong with my Tikka T3?

[timotheius]

I need some help figuring out if something is wrong with my gun, my load, or me....maybe some of you can figure out what is going wrong. As you can see from the pic of my target I shot 3 groups of 4. The first group is pretty sweet. I would be thrilled if all my groups were like this. The second groups is decent, but clearly is opening up a little bit. The third group opens up a lot. What is causing this? Have I worked up a load that it too tempermental?

My gun is a Tikka T3 light in .243. I added an aftermarket Bell and Carlson stock with a full length aluminum bedding block. The barrel is free floated. The load is 100 grain Sierra pro hunter bullet, Hornady Brass, fire formed and neck sized with a lee collet die, 35.6 grains of IMR-4064 powder, Winchester primers.

My gut feeling is that this may be caused by barrel heating? The Tikka T3 light is a light hunting barrel. But will a hunting rifle open up groups like this after only 8 shots? I didn't shoot them all back to back to back. I did wait a few minutes between groups. I'd say these 12 shots took about 20-30 minutes to shoot. Am I seeing the groups open up as the barrel warms up?

 

[FearNoWind]

Have I worked up a load that it too tempermental?
I doubt that. Your groups open up "consistently" from one target to the next.
A load issue wouldn't reveal itself in that way.
My gun is a Tikka T3 light in .243. I added an aftermarket Bell and Carlson stock with a full length aluminum bedding block. The barrel is free floated.
What's the clearance between the stock's barrel channel and the barrel?
Is it "free floated" all the back to the recoil lug?
Is the recoil lug pinned?
What's the torque on the action screws?
It's mounted in a bedding block but is is "bedded" entirely?
My gut feeling is that this may be caused by barrel heating?
That's a good possibility in a rifle as light as the Tikka T3 light.
But will a hunting rifle open up groups like this after only 8 shots?
That's certainly a possibility but if you haven't finished the job with the first two shots you should probably hunt less and practice more.

Horizontal stringing can be caused by several factors, including shoulder position and pressure, rear bag positioning (if you use one) barrel overheating, poor bedding, incorrect torque of action screws, barrel (even when "free floated") contacting the stock as it heats up, etc.
Are you shooting from a rest? Bipod? Bench? Off hand positions? Sling? Prone?
There are a number of factors that need to be considered in finding a solution to your problem

 

[HARPERC]

Is it repeatable or is this the first time it's done this?

A lot of good questions in the prior post, another might be what are your expectations from a light, off the shelf rifle?

Heat is certainly one issue to look at, but to me if it will keep doing that with the first four I'd be happy. Actually the first 8 are still decent.

Ambient temps are going down bit, let it cool completely between groups. Might be interesting to let cool completely between shots.

 

[Pdvdh]

My two Tikka T3 Lites in 7mm RM will open group size after 3 shots fired. Yes, the skinny tube will heat rather quickly compared to heavier contoured barrels, and is more susceptible to expanding group sizes.

There's a lot of other stuff that might be going on. Shoot 3 shot groups and then let the barrel cool. If you haven't killed an animal by the 3rd shot, it's time to head back to the shooting range and figure out what's gone wrong.

No need to shoot 4 or 5 shot groups. That is, unless you want to Post on the Sniper's Hide forum. Then I think you need minimum 100 shot groups, or they'll ban you for life. Less than 50 shot groups and after they ban your ***, they'll then report you to the IRS!

 

[Rick Richard]

You need to repeat the same procedure and see if it can be replicated. I would suspect the barrel may be in contact with the stock. Also, shoot three with a cold barrel and let it completely cool and then shoot another string.

I had a Tikka T3 300 WSM and replaced the stock with the exact stock as mentioned. I had to remove material from the stock for proper clearance.

PS. If you expect an issue with the gun, I would not send it back to Baretta for an inspection. They will just take your money and indicate nothing is wrong with the product. This is based on previous experience and disappointment.

 

[ShootnMathews]

Lots of good thoughts and questions posted. My gut tells me it's just from barrel heating, especially if it was a warm day. It takes the barrel a long time to cool if the ambient air around it is already warm.

But I will give one other possibility that I experienced first hand one day. Shooting off of sand bags I didn't notice that each time I shot the sandbags were moving forward on the stock and the sandbag was actually touching the barrel for the last few shots. Made my group open up in a similar fashion.

I would try this. Set up on evening and shoot a 3 shot group. Put the gun away. Repeat this a few evenings and see if each 3 shot group looks like your first target in the last post.

 

[timotheius]

Thanks everyone for the responses and good information. I'll try to answer some of the questions that were posed.

The barrel is free floated so far as yesterday I took 2 one dollar bills and was able to slide them all the way to the receiver. However, the barrel still looked close to stock, maybe some additions inletting is necessary. The action is mounted to the bedding block, but the action is not otherwise glass/epoxy bedded. I don't have a torque wrench, so I can't tell you what the action screws are set at, other than I just hand tightened then up a tight as I could get them. I shoot from a bench off a Sinclair varminter rest, and a protektor rear bag.

I agree that it is in great form for hunting. No, it will not take me more than 1 shot to get the job done on a whitetail. But I am relatively new to the world of precision ammo hand loading and target shooting. Prior to this, my whole life I just assumed that you could get a good hunting gun and if you were a good shooter you could grab any box of factory ammo and shoot tight groups all day long. I guess I never before realized all the factors that actually come into play that can limit a gun's accuracy. If you ask what my expectations are, I guess I would say I'm posting this thread because I'm not sure what results I should be able to expect.

You are all right, I need to see just how repeatable these results are. I just developed this load last week. I found my Tikka .243 to be very finicky in what it liked and didn't like. It took me a long time to find this load and COAL. (but then again, I have only been handloading for a year and a half now, and I know there is a big learning curve) I will load up several 3 shot strings and take it to the range this week, giving it 10-20 minutes to cool between groups. I'll see just what it does. I will also look at the action and beddin block, and see if some additional bedding and free floating might be in order. Thanks for the help.

 

[timotheius]

oh, and I will take another pic of my results and post it here as a follow up

 

[d11r529]

Next time your at the range trying sliding the 2 one dollar bills checking your free floating job after each group. If they stick it will not only tell you that you need to open it up a little more but where.

 

[timotheius]

that's a great idea. thanks!

 

[wbm]

Target 1 shows me that you have a great load that the rifle shoots extremely well. You can't expect bench rest barrel performance from a light weight sporter barrel. Ain't gonna happen! Therefore, three shot groups is the norm. What you are really after is a bullet powder combination that shoots great....I think you have one.

 

[Deleted member 46119]

I see barrel heating over a good load.

 

[FearNoWind]

Tim, you eluded to a factor that a lot of huntsmen-reloaders who may be new to the sport struggle with and get very frustrated about.
Those of us who shoot competition with heavy barrels and even heavier rifles are accustomed to putting lots of rounds into small targets. But the lighter hunting rifles are often incapable of putting fifty rounds into a tight group within a short period of time. When they're working up a load, the huntsman-reloader with the light rifle often finds the first set of test loads looks pretty good but the next two or three sets look pretty bad. The result can be that they are lured into believing that the loads that didn't print well on target aren't worthy of using. So they chase a good load with bad data.
When you're working up a load with a iight rifle, take the entire day. Shoot the first set, put the rifle in a cool environment and wait until the rifle cools completely, then the second, and so on. Your "on target" data will be far more meaningful using that method.

 

[timotheius]

FearNoWind, you pretty much described my last year or so of wasted time, powder, bullets, and data....not to mention spending hundreds of dollars chasing the next magic reloading tool or shooting accessory that was sure to cure my accuracy problems. I had no idea that heat could cause these results. You are absolutely right, the next time I work up a load I will take several hours and make sure the gun completely cools before testing each group. Wish I had figured this out several months ago.