consistent odd grouping

[Mungo]

I have an ongoing accuracy problem with a Sako 75 in .243, and would be very grateful for input.

After a previous consultation on here, I got the rifle glass and pillar bedded by a respected smith.

It now behaves extremely predictably:

First shot from a cold barrel is dead on. First shots from successive groups fired 5 mins apart overlap. In fact, if i just took the first shot from each group, they form a single ragged hole.

Second shot from a group goes 3 inches right and an inch and a half up. Again, very consistent - forms a respectable group of its own.

Third shot from a group ends up roughly in between first and second, but with less consistency.

So: what's happening and what can I do?

 

[Muir]

I have an ongoing accuracy problem with a Sako 75 in .243, and would be very grateful for input.

After a previous consultation on here, I got the rifle glass and pillar bedded by a respected smith.

It now behaves extremely predictably:

First shot from a cold barrel is dead on. First shots from successive groups fired 5 mins apart overlap. In fact, if i just took the first shot from each group, they form a single ragged hole.

Second shot from a group goes 3 inches right and an inch and a half up. Again, very consistent - forms a respectable group of its own.

Third shot from a group ends up roughly in between first and second, but with less consistency.

So: what's happening and what can I do?

I used to get that from Ruger factory barrels from the 1970's. No bedding, cleaning, prayers or bribery would make the 2nd and third shot go to their older brother. I finally came to the conclusion that the barrels just weren't good. I rebarreled all of them.~Muir

 

[Akeld]

Have you tried different ammunition (assuming factory) or tried a different bullet or played with seating depth if reloading, or as Muir suggests it might be the barrel, although the Sako's are usually good. Does the smith who bedded it have a bore scope? Always worth getting someone else to shoot it as well just to rule out shooter error

 

[Mungo]

Have you tried different ammunition (assuming factory) or tried a different bullet or played with seating depth if reloading, or as Muir suggests it might be the barrel, although the Sako's are usually good. Does the smith who bedded it have a bore scope? Always worth getting someone else to shoot it as well just to rule out shooter error

I haven't tried different ammo, but given the consistency with which this happens, I don't think the ammo is the problem. With an ammo issue, wouldn't you just expect a big group, but without the very regular pattern within a shot sequence?

I don't think it is shooter error, becuase: (i) the consistency; and (ii) I was alternating between the .243 and a .270, and was shooting my .270 perfectly well (I imagine it's pretty unusual to be getting better grouping from an unmoderated .270 than from a moderated .243!). Shooter error is my default explanation for any problems, and I think I can rule it out here.

 

[Shadrach2986]

Could it be moving ever so slightly in the bedded stock thus given you a double group! I think they call it double pinching on the action,

 

[Moray Outfitting]

I refer to my standard caveat regards rifle barrels - 9/10 witchcraft!

I have come across this with various rifles across several makes. I have a suspicion - but must be honest that's all it is. The most worrying instance was decades ago with a certain major urban police force. At the time they had 22-250 & 243 Parker Hale 1200's as their sniper rifle. I noted a 'range card' on the stock of each and thought a good idea - until I read it! It went along the lines of 1st shot 'on', 2nd within 20 seconds 3" low/5" left, 3rd shot - and so on. Pity the second hostage in the 'queue'!

The worst offender was a 7mm-08 A bolt that pulled off some atounding results for me, but honestly - you never really knew what it was going to do next.

From the symptoms you describe I think the issue lies with the barrel. Its a matter argued to the point of Fatwa on here - so I'll re-iterate its just my best guess, I'm really not interested in duelling over it

Machining/ manipulating a barrel induces stress. The exact nature of that stress is hard to predict - but heat treatment is fairly advanced as a science and often deployed to relieve stress as much as achieve a given temper etc. Heat causes a reaction in metal - it wants to move. Forces of expansion/ contraction are massive. I have seen a barrel exhibit similiar symptoms - having been previously 'fine' - close examination showed a ding in the metal about 6 inches ahead of the chamber - not sure what that proves or otherwise, but it wandered shots as the barrel warmed thereafter.

Mike Norris penned a post on a thread about barrel break in ( another Fatwa inducing topic ) and from recollection relayed advice relating to similar behavious from barrels not conditioned and the inflammatory view ( relayed by him from another ) that often once the conditioning process was bypassed, a barrel may never fully respond. I'm not suggesting a break-in/ comditioning issue here. Just as example.

I think Craig Boddington referred to similiar symptoms - but dont recall where - which were alleviated to some extent by Cryo treatment on the barrel.

None of that provides a solution I'm afraid, just a possible root. It could be that the bedding has merely settled the pattern into something more predictable?

 

[Mungo]

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.

 

[Conure]

It sounds like something is moving despite the beddign job and I will bet that the barrel is free floated too.

I am going to suggest that yon dampen the barrel. Get a glazed business card and cut into strips and place under the barrel about 1" back from the front of the stock so that there is upwards pressure on the barrel. Hoping that you do not have a stock with enough gap here to swallow a herd of elephants and try it. pressure needs to be enough to hold barrel in place and dampen the pulses of the firing cylce.

Not my idea so cannot take the credit as pressure pont beding is as old as the hills and the card trick came from a thred about free floating and how it did not suilt a rifle but pressure point bedding sorted it out.

http://www.go2gbo.com/forums/bolt-a...ra-land/stock-barrel-pressure-point-question/

and one from the archives of this very forum ..

http://www.thestalkingdirectory.co.uk/archive/index.php/t-85897.html

Just a suggestion of course and apart from a little time a cut up card and a few rounds what is there to lose?

 

[bewsher500]

crap barrels don't show consistency

my money is on action/stock interference

especially if the shot sequence is "walking" in a roughly similar direction

 

[Mungo]

It sounds like something is moving despite the beddign job and I will bet that the barrel is free floated too.

I am going to suggest that yon dampen the barrel. Get a glazed business card and cut into strips and place under the barrel about 1" back from the front of the stock so that there is upwards pressure on the barrel. Hoping that you do not have a stock with enough gap here to swallow a herd of elephants and try it. pressure needs to be enough to hold barrel in place and dampen the pulses of the firing cylce.

Not my idea so cannot take the credit as pressure pont beding is as old as the hills and the card trick came from a thred about free floating and how it did not suilt a rifle but pressure point bedding sorted it out.

http://www.go2gbo.com/forums/bolt-a...ra-land/stock-barrel-pressure-point-question/

and one from the archives of this very forum ..

http://www.thestalkingdirectory.co.uk/archive/index.php/t-85897.html

Just a suggestion of course and apart from a little time a cut up card and a few rounds what is there to lose?

Thanks! I had heard (and thought about) this. I will give it a go.

 

[Mungo]

crap barrels don't show consistency

my money is on action/stock interference

especially if the shot sequence is "walking" in a roughly similar direction

What would you look for?

 

[Erik Hamburger]

I suffered from 'stringing' and obviously I blamed my rifle (Howa 1500 .243 stainless Sporter) and scope (Sightron Series 11 fixed 6x42) and my bullets (Federal Power-Shok 100Gr SP) . I even blamed my wife.
However going to a rifle range and being observed by a good instructor (Paul Hill, Corinium Rifle Range) he slightly changed my position and breathing technique, and suddenly the rifle performed fine.
Your shooting (rather than your equipment) is possibly another thing to consider when you experience accuracy problems.

 

[Mungo]

I suffered from 'stringing' and obviously I blamed my rifle (Howa 1500 .243 stainless Sporter) and scope (Sightron Series 11 fixed 6x42) and my bullets (Federal Power-Shok 100Gr SP) . I even blamed my wife.
However going to a rifle range and being observed by a good instructor (Paul Hill, Corinium Rifle Range) he slightly changed my position and breathing technique, and suddenly the rifle performed fine.
Your shooting (rather than your equipment) is possibly another thing to consider when you experience accuracy problems.

As said, operator error is always my first guess. But I was alternating with another rifle, and shooting fine with that.

 

[ejg]

It is so funny how a barrel change solves all these little problems.... a good barrel shoots off the bench bedded or not (differing shooting positions..different story). I had wasted so much time with a duff factory barrel that most of my rifles now all have match barrels. The barrel is the most important part of a rifle, that is where one should spend money not on the action.
edi

 

[Mungo]

It is so funny how a barrel change solves all these little problems.... a good barrel shoots off the bench bedded or not (differing shooting positions..different story). I had wasted so much time with a duff factory barrel that most of my rifles now all have match barrels. The barrel is the most important part of a rifle, that is where one should spend money not on the action.
edi

I can't bear the thought of dropping even more money on this. What would a new barrel cost? Another 5-700 quid?

No - if I can't solve it now by hand, it's going.

 

[Heym SR20]

Is that barrel still warm on the 2nd shot?

I get exactly the same behaviour with the 7x65r albeit 2nd shot goes high and a less extent with my Heym 243. However I can live with it as 90% of the time its the first cold shot that is required - if a 2nd rapid shot is needed then I need to remember to aim off slightly.

But was it doing this prior to bedding. I would speak with whomever did the bedding job.

 

[Alantoo]

If it is barrel warming...

I have a not dissimilar problem and was wondering about taking a 12 volt battery and car boot mini compressor with me to the range to blow air up the barrel after each shot...haven't plucked up courage yet.

Now I have spoken it out loud as it were, I realise I have a Hilti resin anchor hole puffer (bike pump on steroids) which would put a greater volume of air through faster...or even a pair of fire side bellows.

Not much good when you wish to take a second shot in the field, but may help to speed up the problem solving at the range?

Alan

 

[N.F.W.M]

If it is barrel warming...

I have a not dissimilar problem and was wondering about taking a 12 volt battery and car boot mini compressor with me to the range to blow air up the barrel after each shot...haven't plucked up courage yet.

Now I have spoken it out loud as it were, I realise I have a Hilti resin anchor hole puffer (bike pump on steroids) which would put a greater volume of air through faster...or even a pair of fire side bellows.

Not much good when you wish to take a second shot in the field, but may help to speed up the problem solving at the range?

Alan

That made me laugh, I had a problem .243 that I could not get grouping and I resorted to using a compressor blasting cool air down the barrel....... Didn't make a farts worth of difference !

Mungo.......May I suggest that after the recent work that you check that the front action screw has not been left a fraction too long and therefore interfering with the cheek of the bolt lug and affecting concentricity. I had this happen and it created many accuracy problems until resolved.

 

[Mungo]

But was it doing this prior to bedding. I would speak with whomever did the bedding job.

It was worse prior to bedding:

Before: POI would shift between groups. First two shots of a group would clover-leaf, then shots would wander. Let barrel cool, next two shots would clover-leaf, but often somewhere else (up to 3 inches away). No consistency with wandering, and no consistency of POI between groups.

Now: first shot of a group practically goes through same hole as first shot of previous group. Second shot cloverleafs with second shot from previous group, about 2 inches away. Pattern repeats very consistently group to group.

I agree that since, most of the time, it's only the first shot that matters, this isn't a disaster. However, I would like to be able to take a second shot without having to think about it (the last place you want to be worrying about holding off is when you need to take a second shot in a hurry).

 

[Mungo]

Mungo.......May I suggest that after the recent work that you check that the front action screw has not been left a fraction too long and therefore interfering with the cheek of the bolt lug and affecting concentricity. I had this happen and it created many accuracy problems until resolved.

Good idea - thanks.

How would I detect this?