Crack in SVT barrel??
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Thread: Crack in SVT barrel??

  1. #1
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    Default Crack in SVT barrel??

    Ever see anything like this? I bought this '42 refurbed original sniper and didn't look at it too hard for about a year. Finally got around to taking it to the range but upon stripping saw the apparent crack shown in one photo. Looked so convincing I was even considering having it legally deactivated to sell but on a whim I took a fine file to the area and......it went away with removal of a very small amount of metal. I removed the sight base so I could carefully inspect the entire barrel reinforce and have even looked it over with a high powered microscope using flourescent dye and UV light. Not a hint of a flaw where the original "feature" was so I fired it carefully and then put about 50 rounds through it prior to the after photo. Quite happy as this rifle has the best bore of my 4 refurb SVT snipers. At the range the other usual problem of the repro mounts not fitting properly reared its head. My little copper bush that I put in the notch was chewed up after too few rounds. New fix is a quarter inch brass pin that fits into the reshaped hole in the mount which is lowered by filing such that the pin now is a sliding fit on the top of the notch. Scrapped the spring buffer as useless. Not pretty- kind of agricultural but I'm hoping this will be the ticket for long term use of my snipers without damaging the notch. I should mention that at the range it was showing decent potential (5 shot 3 inch groups with 3 usually in about an inch) with Chinese light ball until the copper bush started to fall apart.

    Ruprecht
    Attached Thumbnails Attached Thumbnails DSCN2584.jpg   DSCN2587.JPG   DSCN5107.jpg   DSCN5129.jpg   DSCN5130.JPG   DSCN5133.JPG  


  2. #2
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    I would be hesitant to shoot it only because of a somewhat similar looking but non-firearms related experience at the place I work. A few parts had "cracks" that were determined to be casting flaws that were supposedly removed by lightly sanding the area. The marks disappeared. During testing though the parts were falling at that spot and one that was cut and sectioned for examination showed that they were indeed cracks that the polishing process had simply blended in. All of them had to be magna fluxed after that to look for flaws.

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    racerguy00: That is, indeed, a concern. I think the thing on mine was more of a machining glitch, if such a thing is possible, although I guess there could have been an earlier precursor flaw. I wondered about the possibility that metal could be smeared over a flaw by polishing so I only used a file and examined it carefully as I progressed. I think that if there were a crack of the size shown that some part of the fracture should be visible after light filing but, as I mentioned, have been over the full area with a microscope. Maybe magnu- fluxing is still in the cards given the size of the original feature. Thanks for the comment!

    Ruprecht

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  5. #4
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    That ain't no surface flaw, that my friend is a crack.
    Proceed to magnetic particle inspection.

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    NDT non destructive testing Magnaflux and Ultra sound testing to see how deep it goes

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    Thanks guys, I'll start looking into where I can get this done. Any specific comments regarding the proper way to do it with a rifle? As far as the flaw itself goes, I'm no engineer- all my knowledge of fractures is from the world of structural geology but the principles are the same whether in granite or steel. Two additional observations that led me to think this might not be a real fracture were: 1) many machining striations end at the feature which shouldn't be the case if it's a simple pressure induced tension fracture (ie happening long after final machining). Suggests something was happening when it was machined. I guess with wishful thinking I hoped that it might be strictly an artifact of the machining process itself but, as racerguy suggests, it could reflect a preexisting flaw from casting/forging? 2) The geometry of the feature isn't what you would expect of a simple pressure induced fracture. As shown on the photo, the plane of the feature is parallel to the bore axis but oblique to it. A simple pressure induced tension fracture should be normal to the barrel surface as well as parallel to the bore, should it not? So, maybe a pre-existing flaw from forging of the blank? Again with more wishful thinking, perhaps it's something other than an open fracture which would be consistent with not seeing even the faintest hint of a flaw on the gently filed surface.

    When I test fired this I put 5 rounds through it with the rifle on a led sled and using a string. I then lifted the handguard and looked for any change before doing more firing. It'll now be relegated to the safe until I can get something more definitive done. Thanks again for the comments.

    Ruprecht
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  8. #7
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    That's not a crack, it's a large scratch. It started on the rear sight base collar and scratched across the base of the barrel. Go look again, you can clearly see it's one continuous scratch.

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    Look at it through a 10x magnifying glass or loop. You should be able to tell the difference between a scratch and a crack. Personally, I think that if it was a crack, it would have let go after firing it over 5 times – especially with its direction and location - if it is a crack, then it is ABOUT to let go!!!.

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    Claven and Tombstone: As it originally appeared I couldn't easily convince myself that it was a scratch but given how easily light filing seemed to eliminate it it is a possibility. I have stared at it both before and after with a Zeiss-Jena high powered microscope and, as mentioned, can no longer see anything at all where the feature was.

    Ruprecht

  11. #10
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    Quote Originally Posted by Ruprecht View Post
    Claven and Tombstone: As it originally appeared I couldn't easily convince myself that it was a scratch but given how easily light filing seemed to eliminate it it is a possibility. I have stared at it both before and after with a Zeiss-Jena high powered microscope and, as mentioned, can no longer see anything at all where the feature was.

    Ruprecht
    there's no way it was a crack to begin with. The type of hoop stress radiating fro the chamber would not have caused a single linear surface crack like that without propagating from the chamber side of the barrel. Your brass would have shown evidence of flowing into a crack, you would have got hard extraction, and in all liklihood, the receiver would have shown failure indications.

    It's a scratch. You filed it away and that further serves the scratch hypothesis. If it were my rifle, I would no longer be concerned about firing it.

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    I bought a GEW-88 a couple of weeks ago that was covered in filth. When I cleaned it up, there appeared to be two parallel cracks running down the barrel shank. Needless to say, I was disgusted. After carefully examining the ends I began to think scratch. Even under a dissecting microscope I could not determine for sure whether it was a crack or just surface damage. I brought out a jewelers file and took off a little of material over the "crack" and determined that it was indeed a shallow scratch. I confirmed that by shooting the snot out of it.

    I hated damaging the finish, but it was an "in-the-white" finish. I carefully blended the filing with a polishing agent. A few years of oxidation and it will be back to normal, as much as possible. If I had discovered that the damage was a crack I would have felt it my duty to part the gun out and destroy the barrel. I could not live with the notion that I passed off a gun that might do some future collector serious injury.
    Aut Pax Aut Bellum

  13. #12
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    I think it is a crack. There is no displacement of material to the sides or along the axis which would be expected from a scratch. The path of this feature is is not straight; it is deflected in the remnant machining grooves as you would expect when a plane intersects an uneven surface. Forging flaws etc should have been fully cleaned up during the machining process. The tool marks are transected by the feature (crack).

    Cracks do not require very large forces to propagate. Moderate stress, combined with an imperfection that concentrates the stress are needed for crack initiation. Propagation of an existing crack requires very low forces. These forces are not necessarily associated with the stress of firing a rifles.

    An effective way to identify very fine cracks on smooth surfaces is to wipe alcohol onto the surface and carefully observe the pattern of evaporation. If there is a crack present, the alcohol will evaporate last from the area of the crack.

    Attachment 2142402

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    Does not look like a crack to me at all. Looks like manufacturing chaff. That receiver is roughly finished to begin with which furthers the theory. One of the biggest clues why I don't think it is a crack is that it is razor straight. Cracks may be created by weak points, but they are random.

    Regardless of what anyone here says, we can't physically see the rifle. Others make valid points and have great stories but they don't matter. It's your rifle and you need to decide how much risk you want to take. Magnaflux or other method of crack locating would be my next and last step.

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    Isn't it amazing that you can come to the Web and get clear and concise answers to questions that are of life and death importance. Thank God for Al Gore!
    Aut Pax Aut Bellum

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    Quote Originally Posted by MarksmanTim View Post
    Does not look like a crack to me at all. Looks like manufacturing chaff. That receiver is roughly finished to begin with which furthers the theory. One of the biggest clues why I don't think it is a crack is that it is razor straight. Cracks may be created by weak points, but they are random.

    Regardless of what anyone here says, we can't physically see the rifle. Others make valid points and have great stories but they don't matter. It's your rifle and you need to decide how much risk you want to take. Magnaflux or other method of crack locating would be my next and last step.
    I don't like how the "scratch" goes up and down zig zag fashion as it goes over the tooling marks.
    To me a scratch will be straight at least part of the way across, not zigging up and back down.
    Your rifle, your ass, your money to pay for a magnetic particle inspection which can be done by any competent automotive machine shop for probably $25, if not less.

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    Thanks again for all the input. I'm ignoring no-one, believe me! I think it would be kind of nice to actually locate a friendly shop that would be willing to do the magnetic testing for this and future possible anomalies. Having said that I will reveal that my conclusion is that its a linear indentation. Look at the attached photos- the second shows the trouble spot again with sight base removed. Note it's not blued under the sight base and it hasn't been touched with file or anything. Absolutely not a hint of a flaw in 360 deg of barrel under the sight. Why would a nasty fracture stop at the end of the barrel reinforce and not extend at least some distance along the barrel? First photo shows original image doctored a bit. This shot is illuminated from the side and you can see how the feature is lit up- clearly the north wall of a trough-like feature. You can also see the lit up "scarp" running up and down over machining grooves. Now for my final observation- just for fun I grabbed a '41 Izhevsk barreled action that was lying around and quickly had a look. Unbelievably there is a very similar feature on the bottom of the barrel (adjacent to the "2"). What are the odds that there are similar cracks on the barrel reinforce of 2 of my SVT's (both purchased as unfired post refurb). Is it possible that the tools used to hold the barrel during installation are putting linear indentations in that location. I have plenty of others to check but not today! In the meantime, given the suspicions of several here I won't be using this rifle (or selling it) until I have had it tested.

    Ruprecht
    Attached Thumbnails Attached Thumbnails SVT crack1.jpg   DSCN5135.jpg   DSCN5140.jpg  

  18. #17
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    I was at one time employed rebuilding airplanes used for training pilots, a long time ago. Saw a lot of similar "cracks" on parts that were red taped by the inspector and I was told to replace. I wouldn't be surprised if that isn't a material flaw, that become more prominent do to repeated stress. Personally I would not trust it...

  19. #18
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    An auto machine shop should be able to magnaflux it.
    I have found cracks in hydraulic valves with a torch, clean the surface with solvent then in your case apply some light oil to the area and let it set for a while, wipe the excess oil off and then gently heat the area with a torch if oil has seeped into a crack it will run out under the heat. You do not have to get it very warm, not much more that too hot to touch, if oil flows out it is a crack, it won't be hard to see.

  20. #19
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    Look at this photo from your original post. You can see the scratch along the reinforce is continued on the rear sight base collar.

    It looks like the rifle was dropped against something as it slid forward, like a sharp rock or piece of metal, and stopped at the receiver face.

    I still vote scratch.



    Plus, if it were a crack propagated that badly, it would not have lasted for 5 shots without worsening visually.

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    Quote Originally Posted by Claven2 View Post
    Look at this photo from your original post. You can see the scratch along the reinforce is continued on the rear sight base collar.

    It looks like the rifle was dropped against something as it slid forward, like a sharp rock or piece of metal, and stopped at the receiver face.

    I still vote scratch.Plus, if it were a crack propagated that badly, it would not have lasted for 5 shots without worsening visually.
    Claven2: With gun in hand it didn't look like a simple scratch to me. If I had been convinced it was I wouldn't have done the experiment with the small file to see if it had depth to it. Rifleman55: I tried that with kerosene with flourescent dye in it but I didn't see anything suggesting an open crack. As I mentioned, under a good microscope there simply is no visible fracture or crack where the initial feature was. Plus, I'm still blown away by how similar the thing on the other rifle looks- a little more subdued but your eye is drawn to it as a crack on first look.

    Ruprecht

  22. #21
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    Quote Originally Posted by Ruprecht View Post
    Claven2: With gun in hand it didn't look like a simple scratch to me. If I had been convinced it was I wouldn't have done the experiment with the small file to see if it had depth to it. Rifleman55: I tried that with kerosene with flourescent dye in it but I didn't see anything suggesting an open crack. As I mentioned, under a good microscope there simply is no visible fracture or crack where the initial feature was. Plus, I'm still blown away by how similar the thing on the other rifle looks- a little more subdued but your eye is drawn to it as a crack on first look.

    Ruprecht
    It's possible that's where the barrel vice collets cinched onto the barrel when the receiver was spun on at the factory.

  23. #22
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    Light buffing with a dremel see if the scratch or crack is removed without going deep if it goes away you are good to go

  24. #23
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    While it is probably just a scratch, simply sanding, filing, or buffing it away can also make a crack visually “disappear” by burnishing parent material into the crack. Once stress is applied back to the area, it will again ‘open up’ and may visually return. Sanding or buffing can also make it more difficult to detect a crack using UV die-penetrate fluids, as the capillary cavity (crack) has been covered over. Magnaflux and eddy current methods should still be able to detect a crack though.

  25. #24
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    I was certified inspector at US Steel pipe mill /oil country pipe, pipe went through UT testing unit if it had crack or ridges it was kicked out to the grinding table there the crack was ground out and tested with a hand held Magnaflux then back to the Ultra sound testing unit for retesting/wall thickness , you can grind out the crack but needs to be tested with Magnaflux and check to make sure of wall thickness is ok, some cracks don't go deep good luck , nice rifle .

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    A final comment- I'll resurrect this after I get some kind of magnetic particle test done. In the meantime I decided to take apart a few SVT's for annual check and cleaning which gave me the opportunity to have a look at a few more barrels in the location of the feature on the rifle in this thread. Looked at 6, in addition to the posted gun, and found some sort of analogous feature in 4. Of the 4, 2 could be construed to be suggestive of fractures or cracks, although neither is as striking as the posted rifle. Check out the photo of the '41 Izhevsk in post #16. If you click on the photo it blows it up a bit, at least on my PC. This "feature" looks fracture-like but under scope is clearly a linear depression. Maybe Claven2 is onto something with his comments about impressions from clamping collet? In any case, thanks again for all the input and I hope to have the definitive answer about the posted rifle to share.

    Ruprecht

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    It will be hard to use an automotive type magnaflux because the tool must be placed at 90 degrees to the suspected area, which, on a rifle barrel, would not have any metal for the two magnetic legs to be placed against. The legs of the magnaflux are about 4" apart. If the tool were placed in-line with the crack ie. going lengthwise on the barrel, the crack would not be detected.

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    stg44_mg42: Thanks for the info- never seen one used and I wondered if there might be specific issues related to trying to test a rifle barrel/ action.

    Ruprecht

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    Quote Originally Posted by stg44_mg42 View Post
    It will be hard to use an automotive type magnaflux because the tool must be placed at 90 degrees to the suspected area, which, on a rifle barrel, would not have any metal for the two magnetic legs to be placed against. The legs of the magnaflux are about 4" apart. If the tool were placed in-line with the crack ie. going lengthwise on the barrel, the crack would not be detected.
    Okay, how about dye and blacklight then?
    Most professional or perhaps race oriented machine shops can deal with odd shapes, I know the race engine shop I worked at had to check non linear parts all the time..
    It was not my dept so I can't recite chapter and verse but I did lurk over a few sessions so I know there's more than one way to skin that cat.

  30. #29
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    After 36 years of maintenance pipe fitting and fabrication for Du Pont I have a basic distrust for any dye penetrant metal testing around. Over the years we used many different systems and they all had different limitations which we sometimes found the hard way. X-ray or magna flux was just a better less prone to missing things type of method. I do know there are machines and methods to check linier cracks because we often found them and had to scrap large fabrications. Good Luck! Bill
    zeebill live from the hills of West Virginia!

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    Yes, the Al Gore version of the internet is pretty cool.

    I am sure glad he invented it for all the true things I can find, as well as for adding the phrase "hanging chad" to our vernacular.

    I discovered from reading some of Al's brilliant science that my house is already sunk 10 feet under the melted icecap. That is a fact I didn't know.


    Quote Originally Posted by SA1911a1 View Post
    Isn't it amazing that you can come to the Web and get clear and concise answers to questions that are of life and death importance. Thank God for Al Gore!

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    Quote Originally Posted by Stalin's Ghost View Post
    Yes, the Al Gore version of the internet is pretty cool.

    I am sure glad he invented it for all the true things I can find, as well as for adding the phrase "hanging chad" to our vernacular.

    I discovered from reading some of Al's brilliant science that my house is already sunk 10 feet under the melted icecap. That is a fact I didn't know.
    Don't look now, but if you're downstream of the Oroville Dam, you just might wind up with water logged Mosins. http://www.freerepublic.com/focus/ne...q=1&;page=3061

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