consistent odd grouping

https://Immersive-optics.com/
A barrel that was overf stressed in machining (or made of steel that was not stress relieved) will shoot the pattern of shot placement described, and do it quite consistently.~Muir
 
Mungo said:
Sigh - I'm increasingly afraid you might be right, Andy.

I think the one thing I can firmly conclude from this whole sorry experience is that I should never have sold my T3, which shot beautiful groups with every ammo I gave it.
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Has your sako got the floating lug? Could it be that the lug is brdded nicely but there is play between action and lug?
 
Muir said:
A barrel that was overf stressed in machining (or made of steel that was not stress relieved) will shoot the pattern of shot placement described, and do it quite consistently.~Muir
Click to expand...

That's curious, and worth knowing.

Is there any other way of diagnosing this as the problem? Ie. additional tests/changes that could either confirm this or rule it out?
 
Mungo said:
Good idea - thanks.

How would I detect this?
Click to expand...

Using a marker pen, cover the cheek in ink, let it dry then cycle the bolt, I would do this dry firing and live firing, check the ink on the lug after each cycle/firing to see if it has worn off. Thats how I did it. Once identified it was remedied in literally 2 seconds with a file on the proud action screw and rifle shoots like a bug holing dream !

I would also agree with you that at some point you need to stop throwing money at the rifle and bin it off. I wasted a small fortune on the .243 I referred to in a previous post, and never got it shooting tight.
 
NO way that I know to specifically identify stress issues in the barrel. Odd behavoir with heat is indicative only - the rifle not you! Odd 'there' a given :-P

Everyone's missed the key thing - Muir and I were virtually agreeing on something! :tiphat:

I really do not know enough to cover in any depth - purely the symptoms I've seen on occassion seem to fit that as an explanation. The follow on suggestion of trying some temporary business card packing well worth a try - it may 'cure' a variety of potential issues. Craig Boddington refers to that too - I think in 'Make it Accurate'?

A bedding issue cant be ruled out - but I would expect a more inconistent effect if something was awry there.

If you head out this way, then a trip to pick Callum Fergusson's brains may be worthwhile?
 
So - one extra symptom:

If I shoot with moderator off, first shot is to point of aim, second shot it 2 inches down, but horizontally correct.

If I shoot with moderator on, first shot goes to point of aim (after adjusting for a 2 inch drop caused by adding mod). Second shot goes right 3 inches and up 2.
 
Whats your cleaning regime? Have you tried it dirty, or clean if you leave dirty, does it happen if you leave a long time between shots.
 
Mod acts as a counter weight and affects barrel harmonics. Think fire hose held three feet back from nozzle - barrel effectively does that on firing. Key is for it to do it in exactly same way each time - harking back to f opening post - does it go point of aim if considerable left between the two shots? The business card thing is effectively influencing those same harmonics.

I could warn you to take care as you could GO mad with these tings... but I have met you.... :D
 
If I leave the rifle to cool down completely between shots, it shoots beautifully to point of aim.

In fact, since bedding, it does so more accurately than any rifle I've shot. The problem only appears once the barrel starts to warm up.
 
Your symptoms are exactly what I experienced, although your problem could have a completely different cause. I eventually got the barrel bore scoped and found bad throat cracking/damage/erosion. I also had heavy copper fouling that was impossible to remove. I had it re-barreled, I changed nothing else and its now super accurate. Of course it might not have been the throat causing the problem, it could have been Muir's 'stressed barrel' or something else but mine was definitely barrel related.
 
Mungo said:
If I leave the rifle to cool down completely between shots, it shoots beautifully to point of aim.

In fact, since bedding, it does so more accurately than any rifle I've shot. The problem only appears once the barrel starts to warm up.
Click to expand...


This is could preclude any concerns any effectiveness of the bedding job
unless there is more too it
 
So here is a picture to illustrate what is going on:


View attachment 69269

This shows THREE two-shot groups. All the shots from a cold bore are in the single hole at 6 o'clock on the target ring. All the second shots are in the group up and right. The one shot in that group that is a bit off is one I pulled.

This pattern repeats with montonous predictability, with cold bore shots creating a single ragged hole and second shots creating a group that is still under an inch, up and to the right.
 
I don't know the answer but this sounds like a low/no cost option if you could borrow one. I was also interested in the "is the action screw a bit long" suggestion. If it is marginal it might only interfere when the barrel is warm and expansion has taken place. Might be worth grinding a mil off the end.

Best wishes,

David.
 
Akeld said:
Whats your cleaning regime? Have you tried it dirty, or clean if you leave dirty, does it happen if you leave a long time between shots.
Click to expand...
I wonder the same, my .243 Sako 75 shoots fine, and always has done, shock horror, it rarely gets a clean, but i guess we are clutching at straws here.
Cheers
Richard
 
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