Help diagnose accuracy problem Heym sr21
- Thread starter Mungo
- Start date
Not yet - but not because I don't think it's a good idea. Work and a sick kid have got in the way.
Yes, After all the soul searching as to the poor results in the field, When I was able to get to the range, at Bisley I made a point of knowing exactly where my first shot should be,and did not fire again till after I went to the butt and looked at the result in this case high and to the right! I am left handed, (high 12 clicks & right 6) Swaro Scope, made the adjustment then back on the money, I have to add that gun did not like more than 3 rapid shots before it lost zero and needed to cool.
BC......
BC......
Did you ever try to cure the cold bore flyer? Or did you just leave it at that?
Since posting this thread, quite a few people have got in touch indicating that they have had similar issues with Heyms. The emerging theme is that they have a very snug fit at the start of the barrel, and that it doesn't take much for this to start interfering with the barrel as it heats up. The common cure appears to be to get the barrel inletting opened up a bit, and sometimes to re-bed the action. They appear especially sensitive to the torque applied to the action screws - a tiny bit over too much, and things start to go wrong.
What seems to be particularly problematic is that the action and barrel are hand fitted to each stock (which is all very well and leads to a very tight fitting), but then the stock is varnished, closing the gap by just enough to cause problems.
All this depresses me enormously. Rifles seem so much more prone to operational failure than any other category of devices I have ever come across. You'd think that with a basic design that has been unchanged for 100+ years, they would have figured out how to do it consistently by now.
Both my Heyms (SR21 in 308 and SR30 straight pull in 7x57) were pillar bedded at the factory so I would not expect the tension of the action screws to make much difference providing they were tight to start with. I cannot remember whether the barrel inletting needed opening up on the 308 and I never used the original stock on the 7x57 as I restocked it as soon as I bought it. Having said this perhaps the poor grouping with the factory stock on heavier 308 loads could have been due to the inletting although that was some 20 odd years ago and in those days I did not pay so much attention to the stock/action/barrel fit.
Sudden change from tight and predictable groups to spraying is not the crown.
First, check the action screw tightness. Loosen then, then retighten, not all at once, but from one to the other, until you reach proper seating torque.
While you have it apart, I would suggest looking for a cracked stock. Check the recoil lug, rear of the action, screw tightness, crossbolts, etc.
I know you said you did all this, but if there was any play in the action front to rear, the recoil will beat it looser.
If it is too tight on the sides or bottom, a sudden change in wood moisture can change a pressure point, or lead to splitting the stock somewhere.
And buggered threads will give a high torque long unrelated to the compression, so buy some new screws.
First, check the action screw tightness. Loosen then, then retighten, not all at once, but from one to the other, until you reach proper seating torque.
While you have it apart, I would suggest looking for a cracked stock. Check the recoil lug, rear of the action, screw tightness, crossbolts, etc.
I know you said you did all this, but if there was any play in the action front to rear, the recoil will beat it looser.
If it is too tight on the sides or bottom, a sudden change in wood moisture can change a pressure point, or lead to splitting the stock somewhere.
And buggered threads will give a high torque long unrelated to the compression, so buy some new screws.
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Sadly I just left it at that. .....I do hope you find an answer to your guns situation, with the advice you are getting off here surely it can be resolved.
BC..
BC..
So, in case anyone was interested...
... the problem has been solved, and it was the bedding. I sent it off to Brock & Norris, who re-bedded it (and extended the bedding to include the rear tang). They also opened up the first few inches of the barrel channel.
A complete transformation. It shoots everything I feed it at 1" or less. No cold bore flyer, no change in POI as it heats up. Factory ammo that used to struggle to keep inside a 4" group now shoots as well as I can hold. Differences in POI between different factory brands so marginal as to be not worth worrying about.
I had hoped getting it rebedded would improve things enough to make the gun tolerable. I did not expect such a profound change. I'm astonished and delighted.
... the problem has been solved, and it was the bedding. I sent it off to Brock & Norris, who re-bedded it (and extended the bedding to include the rear tang). They also opened up the first few inches of the barrel channel.
A complete transformation. It shoots everything I feed it at 1" or less. No cold bore flyer, no change in POI as it heats up. Factory ammo that used to struggle to keep inside a 4" group now shoots as well as I can hold. Differences in POI between different factory brands so marginal as to be not worth worrying about.
I had hoped getting it rebedded would improve things enough to make the gun tolerable. I did not expect such a profound change. I'm astonished and delighted.
Thanks for the info.
Just shows again most rifle manufacturers don't take enough care with bedding...if they bed at all.
My take is the barrel is the most important part of a rifle, secondly the rifle to stock fit and bedding. Thirdly the stock make/build and way down the line which action is used.
edi
Just shows again most rifle manufacturers don't take enough care with bedding...if they bed at all.
My take is the barrel is the most important part of a rifle, secondly the rifle to stock fit and bedding. Thirdly the stock make/build and way down the line which action is used.
edi
Definitely the bedding or stock touching where it shouldn't. It's dead easy to do yourself, take away some of the stock material around recoil lug first two inches or so of barrel and around the rear tang, buy some Devcon and releasing agent. Watch some videos on youtube for full instructions and jobs a good un.
Yup. See the last but one post...
Amazingly, no. The damage to the screw was so marginal as to be insignificant. I do have replacement screws in case problems reappear.
HI Mungo, just seen your updated post.
Brilliant news! all that worry,concern and dissatisfaction with your choice of weapon all sorted out. Now you can enjoy what you wanted to achieve all that time ago.
BC...
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