How Can I Fix Vertical Stringing?

Improving and repairing firearms. Rifle bedding, barrel work, stock replacement and other ways to improve your firearms.

Re: How Can I Fix Vertical Stringing?

Post by Gwion » 04 May 2016, 12:44 pm

Over lubed firing pin causing hydraulic resistance and inconsistent striking?
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Re: How Can I Fix Vertical Stringing?

Post by Wm.Traynor » 04 May 2016, 1:54 pm

Gwion wrote:Over lubed firing pin causing hydraulic resistance and inconsistent striking?


AHA!
I noticed an hour ago while cleaning the barrel, that the gease that I smeared on the locking bolt, could have entered the hole for the firing pin striker. Grease had definitely come in contact with the striker itself. Note; not to be confused with the firing pin in the bolt. I hosed the striker with G96, on noticing the build-up around its hole and the striker freed quickly.

Good call Gwion :D
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Re: How Can I Fix Vertical Stringing?

Post by Gwion » 04 May 2016, 2:16 pm

Interested to see if it fixes the problem. Only thought of it because a friends rifle had FTF recently and that ended up being the problem. He had never cleaned out the heavy grease from the factory and LIGHTLY lubed it with oil.

Hopefully it fixes the FTF and see what happens with the stringing.
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Re: How Can I Fix Vertical Stringing?

Post by Rocker » 06 May 2016, 3:40 pm

Gwion wrote:Over lubed firing pin causing hydraulic resistance and inconsistent striking?


That would result in vertical stringing only? Not horizontal/random too?

*head scratch*
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Re: How Can I Fix Vertical Stringing?

Post by Chronos » 06 May 2016, 6:06 pm

Rocker wrote:
Gwion wrote:Over lubed firing pin causing hydraulic resistance and inconsistent striking?


That would result in vertical stringing only? Not horizontal/random too?

*head scratch*


I think the theory is it may cause inconsistent ignition giving a range of velocity readings and therefore elevation changes but I doubt you'd see anything at short ranges.

I reckon the elevation issue is directly related to poor action bedding

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Re: How Can I Fix Vertical Stringing?

Post by Gwion » 06 May 2016, 8:36 pm

Chronos wrote:
Rocker wrote:
Gwion wrote:Over lubed firing pin causing hydraulic resistance and inconsistent striking?


That would result in vertical stringing only? Not horizontal/random too?

*head scratch*


I think the theory is it may cause inconsistent ignition giving a range of velocity readings and therefore elevation changes but I doubt you'd see anything at short ranges.

I reckon the elevation issue is directly related to poor action bedding

Chronos


I tend to agree. The greasy firing pin was just a suggestion re: failure to fire.
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Re: How Can I Fix Vertical Stringing?

Post by Rocker » 06 May 2016, 9:14 pm

Makes sense, didn't think of it like that.
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Re: How Can I Fix Vertical Stringing?

Post by Wm.Traynor » 09 May 2016, 4:55 pm

Had another crack at it today with 14 test loads. Only one FTF, about #3 I think. Went off after re-cocking the hammer, as usual. That's better than 1 in 4.

Fired 3 shot groups for each load. All groups strung out vertically but in the last two groups, there were a pair of shots an inch apart with the third 4 or 5" away. Hardly an improvement.
Only the rear band was "tightened", for today's experiment. Now I will have to work on the front. It will be even more difficult and I was hoping to avoid it but there is no getting round it.

BTW, maximum loads were extracted with ease. I've just gotta get this gun to group. It's too good to give up on :)
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Re: How Can I Fix Vertical Stringing?

Post by Gwion » 10 May 2016, 3:30 am

Double grouping, from what i understand, tends to indicate the barreled action is hanging up in the bedding and does not have free battery. The stringing can be upward pressure on the barrel.

I'd give the whole striker system another strip and clean, then lightly oil it; if it has improved but not perfect, there may still be a little crud left in there. If you still get FTF, i'd look at a new striker spring, at the same time look for wear on the striker end of the firing pin indicating that it is being interfered with mechanically, preventing a consistent strike.
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Re: How Can I Fix Vertical Stringing?

Post by Wm.Traynor » 10 May 2016, 9:24 am

Thanks Gwion. I will have a close look at All that :)
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Re: How Can I Fix Vertical Stringing?

Post by Gwion » 10 May 2016, 9:31 am

No worries, mate. Like i said, i know nothing about lever action rifles and this is all from my rudimentary knowledge of how bolt actions work re: accuracy faults. Hopefully some of it translates but i can't give you any further details.
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Re: How Can I Fix Vertical Stringing?

Post by Wm.Traynor » 03 Dec 2016, 11:44 am

Well, here I am again with the promised update. Had to postpone work on the Mossy for a longer term project. The failure to fire was fixed with a no-name, spare spring from a gutted old rifle that my 'smith had lying round. Very handy of them. Worked like a charm :D Thank you Pine Rivers.

I continued to address the vertical stringing methodically, so I thought, by reducing the contact between barrel and fore end. carefully, wood was gouged out and the finish smoothed with coarse abrasive on a socket. Even more carefully, the barrel channel was widened just a little, so as not to leave too ugly a gap. Mongrel came with me to Belmont where we did a Lot of shooting. My results weren't too bad. Groups were a bit smaller, so I figured that in "going looser", I was on the right track.

The following weeks were spent on other things :D to the neglect of shooting stuff but recalling past results, I checked the fore end and found a bit more work to do. Memory is hazy on this work but groups were from 2 to 3" and I wanted better. I kept recalling that in the really bad, strung-out groups, the windage was only 1". Rightly or wrongly, I was encouraged and motivated by that thought and the fore end was removed once again to loosen the fit in the front of the action. Remember, I was trying to be methodical; doing one change at a time so as to isolate the cause of the stringing but there was a catch. The rear barrel band screw was bent again. This was the replacement screw that had been sent Free. Then I recalled that loosening the Original screw was the cause of bending in the first place. Too much time had elapsed since the project had begun for my memory to cope with even this important detail. Asking for another one was Unthinkable so I did something else that was also Unthinkable and straightened it. Too bad if it broke. I had nothing to lose and it worked.

But now, there was a problem. Going loose was not the solution. Still believing that barrel vibration was bending the screw, I tried to think of what to do. I rejected the idea of a rubber screw :twisted: 8-) but later thought of installing an O-ring, to more or less dampen vibration. I was a bit hazy on detail but in almost no time, a ring had been trimmed and inserted between fore end and barrel.

Results at the range yesterday with some "working-up" loads for a new bullet, were Disappointing. The vertical stringing had returned. Loosening the rear barrel band screw in stages was ineffective but the loads weren't too hot as we progressed through incremental increases in charges. Another rifle was tested while the Mossy cooled, after every 3 shots. I wasn't taking any chances at spoiling this experiment by over heating the barrel. The front barrel band screw was tried after re tightening the rear but to no effect and 3 live rounds of maximum charges were left. The front screw was re tightened and the magazine cap screw was loosened one turn. The following group was 2.5" wide, 1/2" deep and close to the middle of the target. The vertical dispersion had disappeared :o :D The rifle was put aside while testing continued on the second rifle, a rimfire, for 20 shots. It came to me suddenly that I had brought the remainder of the original ammo with me. Perhaps there had been the vague idea of testing it too but after changing to a fresh target, I turned the screw in, one half turn. What did I have to lose? I actually hoped that the horizontal spread would shrink a little, even if it increased the elevation. The next two shots were dead level horizontally, right at the very top of the target. Carefully, I inspected the backing board in the area above the group making a mental note of the holes that were present, so as not to confuse them with my next shot. But it was not to be. The RO called a ceasefire :shock: Hmmm. Patiently. I waited while a target change ensued and the third shot, when it happened, formed a group, 1/4" deep by 1.75" wide. Oh Happy Day. :D That is two bullet weights and no vertical stringing. That can't be a fluke, can it?

But here's a thought. That final screw, the magazine cap screw, makes no contact with the barrel. As pointed out Very Early in this topic, the is a blind hole in the underside of the barrel to accommodate the nose of the screw but it makes No contact with the bottom or sides of the cavity. I had forgotten that too. Had I recalled it, I would not have touched it. This gets back to postponing work on projects, only to resume long after the results have been forgotten. So does anyone know why the last screw worked?
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Re: How Can I Fix Vertical Stringing?

Post by Wm.Traynor » 18 Nov 2018, 8:26 pm

2018-11-18 15.00.25.jpg
A better view of the crack?
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The Least Of My Problems
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It is my melancholy duty to inform the forum, that the O-ring fix was no fix at all. During testing at Imbil yesterday, the dreaded stringing reappeared. Examination of the rifle revealed that the mag tube was protruding past the muzzle :crazy: Stripping the rifle revealed a crack in the fore-end :wtf:

You can just see the dried beads of glue.

Hmmm. Not sure if these pics posted in the right order but anyway that was an easy fix. However, the main problem remains. While things were apart it was apparent that the mag tube and barrel are in contact; I think. Much more work to do. In the meantime, don't buy one of these @#$%^ things.
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Re: How Can I Fix Vertical Stringing?

Post by Wm.Traynor » 19 Nov 2018, 7:24 pm

2018-11-19 15.54.07.jpg
For some reason I fitted the mag tube to the barrel. No idea why. This shows how it fits at the muzzle-end.
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The tube has been gently pulled as far forward as possible
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Re: How Can I Fix Vertical Stringing?

Post by Wm.Traynor » 19 Nov 2018, 7:43 pm

2018-11-19 15.57.10.jpg
The tube has been moved all the way back. The blind hole in the barrel is for the turned-down section to fit into. Plainly. the tube is free to move, playing havoc with the elevation, I think.
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Re: How Can I Fix Vertical Stringing?

Post by Wm.Traynor » 19 Nov 2018, 8:43 pm

2018-11-19 16.27.33.jpg
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[attachment=0] That is the tip of a screwdriver between barrel and tube. There is quite a bit of clearance between screw and barrel, never mind the screw's hole. No wonder the tube was able to slide forward.
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Re: How Can I Fix Vertical Stringing?

Post by Wm.Traynor » 19 Nov 2018, 8:50 pm

2018-11-19 16.31.45.jpg
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Yes, this O-ring clamps barrel and mag tube in place but I'm not really serious. There must be a better way to stabilise the tube and reduce stringing.
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Re: How Can I Fix Vertical Stringing?

Post by Wm.Traynor » 19 Nov 2018, 8:57 pm

2018-11-19 16.42.07.jpg
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This is the underside of the barrel, showing the blind hole that the screw is supposed to fit into. You can just make out, at the muzzle end of the hole, a shiny bright area. There is some slight deformation of the perimeter of the hole here, which leads me to believe that the screw has been colliding with the barrel, on its way out of the hole during firing.
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Re: How Can I Fix Vertical Stringing?

Post by Wm.Traynor » 19 Nov 2018, 9:04 pm

2018-11-19 16.41.28.jpg
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This is that pesky screw. At the flat, smooth-turned, tip you can make out a "bevel". I wonder if this has been formed/deformed by colliding with the forward edge of the hole? Well, that's my theory................for now ;)
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Re: How Can I Fix Vertical Stringing?

Post by Wm.Traynor » 19 Nov 2018, 9:13 pm

2018-11-19 16.40.51.jpg
A slightly better view of the "bevel", which is at six o'clock on the flat tip.
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Re: How Can I Fix Vertical Stringing?

Post by Wm.Traynor » 19 Nov 2018, 9:25 pm

The question now remains as to what to do to stop the tube sliding forward. I'll have to think about that but a screw of the right length comes to mind. I wonder if this is a stock screw or a bodgey one and what would they send me if I ordered a new one?
Oh dear, I think I'm starting to lose my marbles :? :crazy:
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Re: How Can I Fix Vertical Stringing?

Post by marksman » 20 Nov 2018, 6:28 pm

I think your approach is very logical
IMHO I do not think this is your problem causing the vertical stringing but I would want the rifle to be solid as you do
it actually sounds to me like the temper of the barrel is not good causing the barrel to warp as it heats up :unknown:
I would try shoot a group very slowly giving a big amount of time between shots to shoot from a cold barrel each shot and see if the vertical is still there
good luck with it anyway :thumbsup:
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Re: How Can I Fix Vertical Stringing?

Post by Wm.Traynor » 20 Nov 2018, 7:15 pm

Thanks for your reply marksman :thumbsup:
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Re: How Can I Fix Vertical Stringing?

Post by Wm.Traynor » 20 Nov 2018, 7:39 pm

At this point, I have only questions. For instance, "What is the proper function of the Magazine Cap Screw?" We know that it holds the cap secure in the tube but the length of unthreaded, turned-down section could have two functions, namely 1) to stop the tube sliding and 2) to apply pressure to the underside of the barrel, as a means of "tuning" the vertical spread. My MCS performs neither function because contact is haphazard, random and unreliable.

And then there is marksman's point about a warping barrel but to test that idea the tube has to stop creeping. Did I mention that the tube can be moved backwards and forwards when the front barrel band (FBB )is tightened firmly? There are cut-outs in the bottom of the barrel and top of the tube for the screw but this fastener does not make enough contact with the mag tube to prevent movement. I am thinking of packing the bottom of the lower half of the band which will raise the whole tube. This will make the MCS fit inside the blind barrel hole. That way both the MCS and the FBB will prevent sliding...............I hope ;)
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Re: How Can I Fix Vertical Stringing?

Post by Wm.Traynor » 20 Feb 2020, 3:07 pm

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Re: How Can I Fix Vertical Stringing?

Post by Wm.Traynor » 20 Feb 2020, 3:41 pm

As you can see from the pic above, pasting with comments is something that I have not mastered HOWEVER, I have fixed this freaking damn gun :D :D :D

Much of the credit must go to In2anity who posted his work on a Marlin 336. His reference to the book by M L McPherson was invaluable, in the end. By that, I mean that bedding my fore end in RTV did not work at all, in reducing vertical stringing. It should be said right here, that all of the mods performed by me over the years might not have acted in my best interests. Yes, this is damn complicated. To simplify, In2anity's fix might have worked had I not hollowed out the fore end, relieved the barrel channel, yada, yada, etc.
To cut a long story :( :crazy: short, after failing initially with the RTV, I went the Whole Hog with McPherson's Method and added the RTV between the front and rear barrel bands and ran a bead of it between mag tube and barrel, from action to muzzle.
THAT made a Very Big improvement immediately. The mag tube stayed in place :thumbsup: That's a plus, eh?! :D
The above pic does not reflect that huge leap, from 6" to about 2". This pic above was of last Saturday's testing at 50 yards where I tried to reduce the string further. Shots 1,2 and 3 were fired with the Rear Barrel Band Screw in the same position (firm but not Really Tight) as it was last month, 24/1/20. The rifle grouped about the same; no surprises there.
Shots 4,5 and 6 were fired after the FRONT barrel band screw was slackened by 1/4 turn. Still plenty of vertical. The rifle was being cooled between 3 shot groups so the barrel would not heat up too much.
Shots 7,8 and 9 were much better from the point of view of string. I blame #9 on the terrible trigger. The rifle cooled during a target change and 10 and 11 were fired. That was the end of the ammo. The group 7 to 11 is only about 1.25" deep. That will do me :D :D :D
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Re: How Can I Fix Vertical Stringing?

Post by Oldbloke » 20 Feb 2020, 3:59 pm

WM. Posted the target for you.


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Re: How Can I Fix Vertical Stringing?

Post by Wm.Traynor » 20 Feb 2020, 5:02 pm

Thanks Oldbloke. I was sure it worked for me :problem: I will double check next time but in the meantime, would you mind telling me how you fixed it please?
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Re: How Can I Fix Vertical Stringing?

Post by Oldbloke » 20 Feb 2020, 5:23 pm

WM. Just go to forum help."how to upload pics

Try this link

viewtopic.php?f=27&t=1011
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Re: How Can I Fix Vertical Stringing?

Post by marksman » 21 Feb 2020, 10:43 am

good on you, good news :drinks:
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