looks like gases leaking past shoulder?

Discussion in 'Gunsmithing' started by greggc1960, Dec 7, 2013.

  1. greggc1960

    greggc1960 Well-Known Member

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    Folks, I think I got a problem here, and need some input. Got my builder back from smith, mounted stock and scope, headed out to break in barrel. First round, bolt closed real hard. Actually sheared/smeared some brass off the head. Touched it off, and the bolt lifted ok. Re chambered ok, and closed again ok. Came out looking clean, no signs of gases anywhere on outside of case. 2nd round closed a little easier, ejected ok, also clean. 3 rd , hard to close, although no brass smearing on head, and powder residu around case mouth. 4th and 5th about the same. 6th round, more residue , farther down the case, and a shiny mark at just above the top shoulder radius, but only half way around. Round 7, hard to close, stiff bolt lift, and more residue. 8th (and last ) round, sounded kinda strange, like tik-bang, lots more bolt lift, shinier half moon around neck, and powder fouling in the rim area. The pictures are of the last shot, I'm just turning the case a little. These are not hot loads, new brass full length sized and trimmed to length hand loads. 338 378 Weatherby. I'm stumped, discouraged, and I'm hoping somebody out there can shed some light on this. Thanks. 20131206_182840.jpg

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  2. barnesuser28

    barnesuser28 Well-Known Member

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    Were you cleaning between shots? If so, you may not have gotten all the bore cleaner out of the chamber. Which doesnt allow the case to stick to the chamber walls and may cause what you are seeing.
     

  3. greggc1960

    greggc1960 Well-Known Member

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    Wow, could it really be that simple? Yes, I was cleaning between shots. So maybe dry it up and try a couple more ? Got some aerosol Rem Clean, would that work? How would it act if the chamber/barrel is not square ?
     
  4. Hired Gun

    Hired Gun Well-Known Member

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    A wet chamber will cause all sorts of havoc. It will make it act like you have massive pressure when indeed none is present. Gas leaks, dents and flattened primers are the big ones. If the bore is wet it can cause damage in the bore. Dry it with some dry patches. No spray.

    A crooked chamber will not show anything on the brass. It can only be seen with a borescope or the best way is taking it apart and dialing the barrel in a good lathe. Then it can only be checked if the same technique is used as the guy that built it. If you check it with a different technique it will show way off.
     
  5. SidecarFlip

    SidecarFlip Well-Known Member

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    I'm with Riley, you have a wet hole.:D

    The soot/swirl marks on the case are real indicative of a wet chamber.

    Far as hard bolt closing, you say you FL resized the brass but did you check the shoulder datum against a previously fired round?

    I typically bump the shoulders back 0.001-0.002. Keep in mind that all bottleneck cases loacate/headspace on the shoulder datum, even your round shouldered Weatherby caliber.

    Contrary to popular opinions, you can bump shoulders with an ordinary FL non bushing die, I do it all the time.
     
  6. Hired Gun

    Hired Gun Well-Known Member

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    How would you bump a shoulder without a fl die?

    A problem with current head space concerns is some smiths are pushing past zero headspace and actually going negative. This can cause a problem where the FL die is not short enough. The only fix is to shorten the die or the shell holder a bit.
     
  7. greggc1960

    greggc1960 Well-Known Member

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    Ok, thanks, that gives me something to chew on. Its fresh from the smith, new barrel and bolt head, so I dont have any previously shot brass. However, I believe that negative headspace thing is in play here. The eight spent cases from yesterday chamber very easily, but the live rounds dont. Takes a bit of work to close the bolt. Last night, I noticed a couple of burrs on the back of the lugs, I could hang my finger nail on them, so I disassembled the bolt head, and carefully filed the burrs off. I figured it couldn't hurt, as long as I did not change the lug length or engagement area. Its a little smoother, but still hard to close on a live round. Think I'll pull a bullet to get an empty, and start fiddling with the shell holder, try and bump the shoulder down. Sidecar Flip, would you explain shoulder datum for me, please? I'm dont know what that means. Thanks to everyone for their time.
    Gregg
    PS Do Savages benefit from bolt lapping? If my chamber is real short, would carefully lapping the lugs help?
    Gregg
     
  8. Clay Target Guy

    Clay Target Guy Well-Known Member

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    Just asking, have your checked your seating depth on the bullet? Could you be having hard bolt closing due to "jamming" the bullet into the rifling?
    Just something else to check.
     
  9. 300rum

    300rum Well-Known Member

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    if you found Burr residue I BET you got some burr inside the chamber and that is the reason why you can not cose the bolt easy.
    go back to gunsmith or get a strong light and look inside the chamber for residual burr left there.
    that is he reason why you have the case neck or shoulder scratched or milled out when you extract them out.
    nothing scarry, but you should do a proper cleaning asap you got your rifle back from gunsmith just to remove the accidentally bur residue left there.
     
  10. greggc1960

    greggc1960 Well-Known Member

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    Yessir, I cleaned it real good, sprayed brakeleen all over and floated everything out, then swabbed the barrel again. It was by no means ready to shoot.
     
  11. 300rum

    300rum Well-Known Member

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    So you did not found anythins inside?

     
  12. SidecarFlip

    SidecarFlip Well-Known Member

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    You can bump with a neck sizer (so long as it has the shoulder taper which most do)(look inside with a flashlight).

    I don't use any neck sizers all my die sets are FL.

    Incidentally, all my FL dies are ground off anywhere between 0.003 and 0.010 at the base to allow for the bump. Contrary to what die makers will tell you (seat the die against the shellholder and 1/4 turn more, which cams over the press linkage), I never do that. I set my dies with a headspace gage using a previously fired case from that chamber and 'bump' the shoulder back 0.001 to 0.002 on a reload.... Which incidentally, is nowhere close to a 'cam over' or a zero clearance fit between the die base and the shell holder.

    Doing that does 2 things. One, it allows the case to load without a hard closing bolt and two, the cases don't 'grow' as much, which means less trimming eventually.

    My only departure from that is in 223-5.56 NATO semi auto rounds which need the full bump to cycle. Those dies are always cammed over to achieve the maximum set back because an auto loader needs a sloppy feed to function.

    I own a 223 bolt rifle too. Those rounds get the first treatment.

    I suspect quite a bit of the 'hard to close bolt' and the 'brass on the boltface' and heavy bolt lift' is attributable to insufficient headspace. Always keep in mind that a bottleneck indexes (for lack of a better word) on the shoulder. If the shoulder isn't concentric with the body or neck, the cartridge lies cocked in the chamber so the pill enters the lands at an angle, not good. Likewise, ant shoulder deformation (like too much lube when resizing causing a dimple in the shoulder is detrimental to concentric loading.

    My suggestion is get a Hornady Headspace gage that adapts to your caliper and use it. They are cheap and you get a good, quick reference as to where your headspace is and what it should be.

    Every chamber is dimensionally cut slightly diffreent because tooling wears and no spindle is perfect (has no runout), at least not in an ordinary shop.

    I just had a poster on this site send me 3 shell holders that he wants to be dimensionally reduced just for the above scenario. In some ways, it's easier to reduce the shell holder dimension than the die base. For me, either works.

    I load a lot of straight wall cases and candidly, they are much easier to work with. They never grow, you can reload them upteen times with no cracking (so long as you are prudent when bell mouthing a case for bullet insertion). I've never annealed a straight wall case either. The only issue is primer pockets. Loose pockets cause the brass to get scrapped.
     
  13. SidecarFlip

    SidecarFlip Well-Known Member

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    You did have a fiired round, the first one you fired would be the one to gage the headspace on. I just did exactly that with a new 6.5x55 Mauser chambered Sako. One round, popped the primer, labelled it (goes in the die box) and thats my check the datum round, that all subsequent rounds will be gaged to.

    The shoulder datum is the theoritical distance halfway between the lower case body, where the shoulder begins and the beginning of the neck and so long as you use the exact same insert bore to check with each time, the datum point becomes unimportant.

    The 'datum' is the check point on which the headspace gage rests when checking headspace.

    Of note is this 6.5x55 Sako. I bought 100 rounds of Lapua brass and checked the headspace against the fired round and had to bump back all the Lapua rounds 0.002 before they were even loaded for the first time.

    If they were headspacing within 0.001 I would have not bumped them, just ran the cases up in the die and allowed the expander ball to run through the necks because with most reloading brass, the necks get deformed in handling.

    For years I just reloaded and never got into this degree of consistency but as the distance increases, so does the degree of preparedness.

    I have a couple guys I build loads for and fiddle with their rifles, who want every round in the same hole. It's doable but things get a bit tedious.

    One of the 'one hole' guys just took a buck at 200 yards with his slug gun btw.
     
  14. greggc1960

    greggc1960 Well-Known Member

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    @300RUM... No, I have not found any more crud in the chamber after I did the initial cleaning. What I have noticed, on all but the first two rounds(remember, its only had 8 thru it at this point), is an obvious influencing of the neck to one direction. I'm thinking this kind of leans towards the liquid in the chamber solution. Too bad, I didn't think to try and find an index for that point. I'm gonna go out in the morning and try to beat the wind for more shooting. I gotta fire form my brass anyway, and as long as it doesn't leak gases around the back end, it'll be fine. I'll know rite away- I have cleaned and dryed everything I can see. If that was the problem, and I tend to think it is, then its solved. Will post more tomorrow.

    @Sidecar Flip...Thanks, I think igot it. Apparently, this chamber is really tight. The spent cases chamber easily. Fire formed, rite? The new cases chamber harder, telling me that possibly, they are longer. The bolt closes, I aint beating on it or nothing, it just takes a bit more effort than I like. And I do see one of them gauges in my future.
    Thank you, everyone, I was definitely freaking out. I'm not pleased with the workmanship on this weapon, and I'm sure that this fact was making a large impact in my thought processes...not that I would have figured it out on my own, this is outside my experience, but I was ready to send it off to another smith to get it "fixed". Thanks again.