Cleaning makes almost no difference here.
First shot from a cold bore after a deep clean is within an inch of the other cold bore shots from a fouled bore.
consistent odd grouping
- Thread starter Mungo
- Start date
Cleaning makes almost no difference here.
First shot from a cold bore after a deep clean is within an inch of the other cold bore shots from a fouled bore.
RPA 6MM BR
Well-Known Member
Highlandsjohn
Well-Known Member
I doubt very much the second shot would generate enough heat in the barrel for it to be a stress problem.
You said the accuracy has been improved by the new bedding. I would suggest there is still some movement after the first shot to knock your second shot off and it is exacerbated by the addition of the mod. as previously suggested.
Something is still allowing some movement, maybe the screw bottoming out, or a wee bit more bedding needed, or the barrel / lug is touching something. Although it is curious with regard to the accuracy returning after the delay. I have a 75 in 7-08 and always had that sideways movement which proper bedding would sort.
Callum Ferguson supplied me with new tork screws instead of the slotted ones, in order to avoid the cost of a (devcon /machined bedding, which more or less fixed the problem I had. I always have got into the habit of making sure the barrel remains central and checking the screws ( such is the cost of being tight fisted
)
Ian's (Yorrick) suggestion is a good one.There are a lot of 75's out there. Try another stock and I believe your problem will go away,jmho.john
You said the accuracy has been improved by the new bedding. I would suggest there is still some movement after the first shot to knock your second shot off and it is exacerbated by the addition of the mod. as previously suggested.
Something is still allowing some movement, maybe the screw bottoming out, or a wee bit more bedding needed, or the barrel / lug is touching something. Although it is curious with regard to the accuracy returning after the delay. I have a 75 in 7-08 and always had that sideways movement which proper bedding would sort.
Callum Ferguson supplied me with new tork screws instead of the slotted ones, in order to avoid the cost of a (devcon /machined bedding, which more or less fixed the problem I had. I always have got into the habit of making sure the barrel remains central and checking the screws ( such is the cost of being tight fisted
)Ian's (Yorrick) suggestion is a good one.There are a lot of 75's out there. Try another stock and I believe your problem will go away,jmho.john
In your earlier thread regarding this problem you mentioned that it had been fine to start off with...
"When I first got it, it shot long groups very consistently (up to 10 shots). The problem has only emerged recently"
...and had developed the fault over 18 months...that would indicate to me that it is not a problem with the barrel being stressed through poor manufacture.
Did you ever try my suggestion of a different sight? That seemed to be the easiest thing to eliminate first.
Alan
"When I first got it, it shot long groups very consistently (up to 10 shots). The problem has only emerged recently"
...and had developed the fault over 18 months...that would indicate to me that it is not a problem with the barrel being stressed through poor manufacture.
Did you ever try my suggestion of a different sight? That seemed to be the easiest thing to eliminate first.
Alan
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bewsher500
Well-Known Member
I agree
usually the barrel is barely warm from one shot
on my 300wm it is barely skin temperature
on my .222 it is still cold to the touch
.243 shooting factory is unlikely to raise the temperature much above 50 deg once it has been conducted through the entire mass of the barrel (seconds)
Yes - tried another sight, and problem persists. Also tried this sight on another rifle, and it performs faultlessly.
The problem is not ammo: the same pattern exists for Hornady, Sako, Federal and Norma, in a range of bullet weights from 70 to 100gr. All that changes is the POI and size of the group shot from a cold bore .
The problem is probably not cleaning: deep cleaning has minimal effect on the placement of the cold bore shot.
The problem is not mounts, since the grouping of the cold bore shot is consistent.
The problem is not me, since my groups with my 270 and 308 are as normal.
The problem is not stock flex introduced by bipod, since it persists when shot off bags or bipod.
It is almost certainly the barrel, the bedding or both.
I am really keen for suggestions of further diagnostic tests.
I will shoot it with a temporary pressure point under the barrel tomorrow and see what happens.
Well I won't claim house level genius or cottage even, maybe somewhere between dog kennel and umbrella...
The starting point in the diagnostic logic sequence is that something has changed from 18 months ago...barrel wear? wood warp? crown damage?
That is my best-est, so now over to a flat or bungalow...
Alan
The starting point in the diagnostic logic sequence is that something has changed from 18 months ago...barrel wear? wood warp? crown damage?
That is my best-est, so now over to a flat or bungalow...
Alan
Not so. If the barrel was overly stressed in machining, one round will cause the second shot to walk. My brother-in-law's Ruger 270 behaved exactly like the OP's rifle. You could overlap the shots and they would, individually, make really good groups. Unfortunately, the first and third shots in any group were about 3.5" apart. We cleaned, bedded, rebedded, re-rebedded, recrowned it, cursed it, kicked it, dropped it and finally, rebarreled it. Problem solved. The barrel, fwiw, looked like it had been rifled by an angry gremlin with a cold chisel. Another scenario is a barrel that has been physically straightened to a large extent. Many factories straighten barrels but when it's really out and pushed back into place, the barrel can flex towards it's original shape.
I can't imagine the OP's SAKO being in this condition, but.... ~Muir
Highlandsjohn
Well-Known Member
There you go Mungo,your Eighteen month problem has at last been solved. If it happened to Muir's brother in law's 270 Ruger it must be stress after all..problem solved
These factory barrels Muir, do they straighten them because the inside (rifleing) or outside is 'out of place' I am genuinely interested.john
Moray Outfitting
Well-Known Member
Eh! I had first dibs on umbrella
Its not only House that gets irrascible
( though I appreciate Muir can have a turn of phrase that rankles and we've been polar on views on any number of occassions 
) I would agree with him ( twice in one thread!!!! ) that a stressed barrel can react to the slightest stimuli. I've never seen Muirs Cousins, next door neighbours 270 etc so cant comment on that.
Trying to leave aside any specific view as to the root -
1. Issue developed - not previously noted. Though if grouping/ accuracy was an issue, could this have masked symptoms?
2. First cold shot - repeatedly, goes to same spot and groups well cumulatively. A bedding issue could well self centre, but the consistent implies it is low on the list. Remember witchcraft card here!
3. From experience as relayed, stress commonly imparted on manfacture, but can occur subsequently - ie ding on barrel that was all but unnoticed. My misbehaving rifle would change over the difference between a warm day and a hot one. - not claiming answer, just relying observation thats as valid ( or not ) as anyone else's.
4. How much do the harmonics of a barrel have to alter the position of the crown at the instant the bullet exits to produce the impact shift observed? I don't exactly know - but not much. Equally, a shift in any other direction of a similiar amount would send bullets all over the shop accordingly. As described, what happens, occurs in a consistent and repeatable way. So the issue can be induced in a repeatable way.
From whats described, the act of firing - yes just one round - seems to produce the effect and the effect is temporary - something occurs over a relatively brief waiting period that restores things to 'cold zero'.
5. Mungo is really irritating anyway and we should just gang up on him until he acknowledges he should have bought Blaser..... sorry, sorry caffeine spike
6. The genuinely irritating thing is I suspect this will get fixed and collectively we'll never know for sure just exactly why this happened.
7. Do you think Mungo noticed #5 above?
Its not only House that gets irrascible
( though I appreciate Muir can have a turn of phrase that rankles and we've been polar on views on any number of occassions ) I would agree with him ( twice in one thread!!!! ) that a stressed barrel can react to the slightest stimuli. I've never seen Muirs Cousins, next door neighbours 270 etc so cant comment on that.Trying to leave aside any specific view as to the root -
1. Issue developed - not previously noted. Though if grouping/ accuracy was an issue, could this have masked symptoms?
2. First cold shot - repeatedly, goes to same spot and groups well cumulatively. A bedding issue could well self centre, but the consistent implies it is low on the list. Remember witchcraft card here!
3. From experience as relayed, stress commonly imparted on manfacture, but can occur subsequently - ie ding on barrel that was all but unnoticed. My misbehaving rifle would change over the difference between a warm day and a hot one. - not claiming answer, just relying observation thats as valid ( or not ) as anyone else's.
4. How much do the harmonics of a barrel have to alter the position of the crown at the instant the bullet exits to produce the impact shift observed? I don't exactly know - but not much. Equally, a shift in any other direction of a similiar amount would send bullets all over the shop accordingly. As described, what happens, occurs in a consistent and repeatable way. So the issue can be induced in a repeatable way.
From whats described, the act of firing - yes just one round - seems to produce the effect and the effect is temporary - something occurs over a relatively brief waiting period that restores things to 'cold zero'.
5. Mungo is really irritating anyway and we should just gang up on him until he acknowledges he should have bought Blaser..... sorry, sorry caffeine spike
6. The genuinely irritating thing is I suspect this will get fixed and collectively we'll never know for sure just exactly why this happened.
7. Do you think Mungo noticed #5 above?
You should know by now - i notice EVERYTHING...
Lucky for you, i have yet to have enough caffeine, so can't muster the air for an appropriately withering retort.
Moray Outfitting
Well-Known Member
I do not know of any specific test for stress and I'm not metallurgic enough to say anything about relieving that stress - I know Boddington mentions Cryo process and I heard once of someone putting a barrel in a freezer for a few days - but no clue whether that would achieve anything.
But, I think the stress issue displays via altering the barrel harmonics. Therefore something like trying some business card packing is likely the easiest and quickest way to experiment. If you get a positive result, then its harmonics - whatever the actual cause. Though maybe the pressure corrected a bedding issue.... you can see where madness lays.
I'd try the business cards in a methodical manner - tiny pressure - shoot three. Let it cool, bit more pressure repeat. Start close to tip of stock - where a pressure pad would normally be. But if results inconclusive, then give it a try placing the packing a little further back toward the chamber. I do not know of any predictable results - because you are dealing with more than SHM - ie single plane harmonics - the barrel end is whipping around like a fire hose. So altering than resonance will impact both X & Y axis vectors.
Like the old BOSS system on the Browning - worked great, but the guide book was useless.
Heavy snow here, so you cant get to me anyway -
But, I think the stress issue displays via altering the barrel harmonics. Therefore something like trying some business card packing is likely the easiest and quickest way to experiment. If you get a positive result, then its harmonics - whatever the actual cause. Though maybe the pressure corrected a bedding issue.... you can see where madness lays.
I'd try the business cards in a methodical manner - tiny pressure - shoot three. Let it cool, bit more pressure repeat. Start close to tip of stock - where a pressure pad would normally be. But if results inconclusive, then give it a try placing the packing a little further back toward the chamber. I do not know of any predictable results - because you are dealing with more than SHM - ie single plane harmonics - the barrel end is whipping around like a fire hose. So altering than resonance will impact both X & Y axis vectors.
Like the old BOSS system on the Browning - worked great, but the guide book was useless.
Heavy snow here, so you cant get to me anyway -
one reason I like shooting 308,.... you test a 308 with 168 match ammo like lapua scenar, if it doesn't shoot that...change the barrel. simple.
I have three 308 rifles with match barrels and haven't found ammo yet that they didn't shoot. Some factory barrelled 308's on the other hand had trouble getting to 1" and were finicky. The barrel is the most important thing on a rifle....get a good one.
edi
I have three 308 rifles with match barrels and haven't found ammo yet that they didn't shoot. Some factory barrelled 308's on the other hand had trouble getting to 1" and were finicky. The barrel is the most important thing on a rifle....get a good one.
edi
With ever post about this I am more and more suspcious of the quality of the work done. My suggestion is to take it to another reputable rifel smith and get them to appraise the work done and if possible bore scope the barrel.
Unless you have dropped it or used it as pry bar to lever your vehicle out of a ditch, the barrel stress cause is a red herring...it would have always been present, from time of manufacture, and it would not show up later as this problem has done.
Something has changed from 18 months ago when it all worked perfectly. That is what you must identify.
Having eliminated something coming loose in the scope, you are back to either a change in the barrel through wear / corrosion / damage....or movement in the wood affecting the bedding / floating.
Alan
ps have just seen your last post...the barrel getting thin enough to reveal stresses which were previously balanced sounds...is all the rifling worn away? How many rounds and what bullets and how hot a load have you fired over the 18 months?
Something has changed from 18 months ago when it all worked perfectly. That is what you must identify.
Having eliminated something coming loose in the scope, you are back to either a change in the barrel through wear / corrosion / damage....or movement in the wood affecting the bedding / floating.
Alan
ps have just seen your last post...the barrel getting thin enough to reveal stresses which were previously balanced sounds...is all the rifling worn away? How many rounds and what bullets and how hot a load have you fired over the 18 months?
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