Chamber? Bolt face? or Dies?

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by Buffalobob, May 2, 2005.

  1. Buffalobob

    Buffalobob Writers Guild

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    Bulged cases

    All of the fired cases come out of my Rem 700 in 17 Rem with a bulge above the case head on one side. This is noticeable if you run a finger nail down the case it will suddenly drop over the end of the bulge right above the web. It is only one side and seems to taper away as you go up toward the shoulder and taper away as you go around the circumference. Every fired case is the same.

    I just full length sized a lot of cases and when they are rolled on a flat surface they are curved. When you stand four or five of the full length sized cases next to each other on their bases it is clear that they are not square with their base. They lean every which way or you can rotate them and get them to all lean in the same direction.


    What is the likely cause of this? Is it that the gun does not have a square bolt face or is the chamber out of alignment or something with my dies. The dies are off the shelf RCBS and were bought with the gun.

    This gun is totally factory stock with absolutely no modifications and I purchased it new in about 1973. It has always and forever for 30 + years shot 0.5 MOA with five round groups with hand loads and 25 gr. Hornady HPs and did so yesterday even though every case has this bulge in it after firing. I assume that this bulge has always been there and I just never noticed it. The bulge is not present in cases that have been full length sized. These are the original 100 cases that were bought with the gun and have been fired maybe ten times and usually only partial neck sized.
    The cases probably need to be thrown away and start with some new ones which are really cheap at $23.00 per hundred.

    I really do not mind the bulge being as the gun shoots as well as I can keep it still on the sandbags and in the field hunting, half MOA is good as I can do on a good day. But if it is just the dies I can certainly afford new dies.
     
  2. chris matthews

    chris matthews Well-Known Member

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    It's your chamber- Remington crams a reamer in there at mach 3 and calls it good. I am suprised the gun shoots that well, because if the chamber is that crooked the throat normally is too.
    If you ever decide to rebarrel it, look me up I am a HUGE 17 fan and have built several of them- minus the bulge of course...LOL!!!!
     

  3. Fiftydriver

    Fiftydriver <strong>Official LRH Sponsor</strong>

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    Buffalobob,

    This is simply a case of the chamber dimensions being on the loose side. When you chamber a round in a loose chamber(factory), the loaded round will sit in the bottom of the chamber if you will. Gravity will pull it down.

    When it is fired, the bottom of the case is already laying on the chamber so the only place for the case to expand is up. The expands the case to fill the chamber and results in the buldge on the one side of the case.

    With repeated firings, this generally will even out all around the case to some degree but is it simply from the chamber being much larger then needed.

    The only way to cure this problem is with a rebarrel job and a properly designed reamer that will limit this expansion and reduce this buldge.

    Once the case is fireformed, and if you neck size or partial full length size, you will generally get good grouping if the rest of the rifle is put together well which it sounds like it is.

    Repeated full length sizing will work harden the brass and could result in some case body splits.

    This is typical in factory rifles, some to a higher degree then others but very common.

    Nothing to worry about and don't try to get rid of the buldge with your case sizing. The case is just expanded to fit your loose chamber and let it stay that way for best results on target!!

    Don;t give it another though and have fun with your little hot rod!!

    Kirby Allen(50)
     
  4. gonehuntingagain

    gonehuntingagain Well-Known Member

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    This seems to be a common problem with the Rem 700's. My gun and 4ked Horn's 308's do exactly the same thing that you are describing to the case after firing.
    Eventually there will be a line that you can feel on the inside of the case around the base (where you see the bulge). If you stick a unfolded paper slip down the inner wall of the case, you will feel a line that feels like a "thin spot" in the brass and may be indicative that a case-head separation will happen soon.

    I have no clue as to why this happens - it may not be just one thing, but a combination of variations that would occur in the mass-production process.
     
  5. Buffalobob

    Buffalobob Writers Guild

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    Thanks everyone, it looks like at least I am in good company with Gonehuntingagain and 4kd horn.

    Chris

    If I should be so lucky to get enough time and shooting to shoot this barrel out I will certainly let you fit me another and work the action over.

    Kirby

    Keep working on those magnums - speed is good and more speed is better.
     
  6. Guest

    Guest Guest

    Wow

    This is a great thread. I also have the same issue in a Win 70 yote. 300 WSM It's amazing the stuff you learn on this site.

    Joe
     
  7. brian b

    brian b Well-Known Member

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    [ QUOTE ]
    This seems to be a common problem with the Rem 700's. My gun and 4ked Horn's 308's do exactly the same thing that you are describing to the case after firing.
    Eventually there will be a line that you can feel on the inside of the case around the base (where you see the bulge). If you stick a unfolded paper slip down the inner wall of the case, you will feel a line that feels like a "thin spot" in the brass and may be indicative that a case-head separation will happen soon.

    I have no clue as to why this happens - it may not be just one thing, but a combination of variations that would occur in the mass-production process.

    [/ QUOTE ]Gonehuntingagain,
    You are absolutely correct IT IS a combination of variations that causes this. #1 saami spec. reamers (that are oversize in comparison to most brass if not all). #2 HEAD SPACE ( if you are getting thin spots in the web area most likely head space is long in the chamber or you are oversizing your brass) Remington is famous for this but absolutely the worst I have seen is Thompsons in some of there contender chamberings where the web of the chamber is .010 larger the head space is .015 longer and the throat is unreachable. this can ruin even the best of brass after only a few firings. that is why most of the people on this forum try an AFTERMARKET experience (custom barrels,snug if not tight neck chambers ,good if not great reloading equiptment and patience with mediocre things that we wished we had control over but DONT.) B.
     
  8. gonehuntingagain

    gonehuntingagain Well-Known Member

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    Brian - I hear what you are saying. 4ked and I determined that on his rifle that he can't reach the lands with a 168gr bullet and have it still seated in the case enough to keep it from falling out. I haven't tried that with mine, and I wouldn't be surprised if it was the same way. I can't wait until I either burn out this barrel or can come up with the $$$ to rebarrel and true the action.
    Until then, I will try to get as much life out of the cases as possible.
     
  9. 4ked Horn

    4ked Horn Writers Guild

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    After a brief discussion with GG I have decided to get the Redding S type bushing neck die and body die to help preserve my bulged brass. I am culling 25% of my fired brass after only 5 firings when FL sizing each time. This is working the brass like a dog and the webs are showing the thin band on the outside of some of them. /ubbthreads/images/graemlins/shocked.gif

    Do I actually have to rebarrel or can I have the chamber recut and set back? How much BBL length would I lose doing this. I am nowhere near burning up this BBL and I do get decent groups as it is.
     
  10. gonehuntingagain

    gonehuntingagain Well-Known Member

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    [ QUOTE ]
    Do I actually have to rebarrel or can I have the chamber recut and set back? How much BBL length would I lose doing this. I am nowhere near burning up this BBL and I do get decent groups as it is.

    [/ QUOTE ]

    You forgot to ask if it would be worth doing with a FACTORY barrel. I guess this would be based on what it would cost to do.
     
  11. 4ked Horn

    4ked Horn Writers Guild

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    Didn't forget. Looking for the cheap way to get a tighter chamber. Just don't want to lose too many FPS.

    I could ask if it would be a better idea to re cut it to a .308AI while we were in there. Would that preserve more BBL length since the cut is more outward (radial) than inward (down the bore)?
     
  12. Fiftydriver

    Fiftydriver <strong>Official LRH Sponsor</strong>

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    4ked Horn,

    It all depends on the dimensions in your factory chamber. I would say taking off 1/2" would probably clean up the old chamber but I would not say for 100%. The problem is that your chamber is obviously very loose.

    Most custom reamers, at least all mine are built to very min specs so what you have is a fat chamber that you are trying to clean up with a skinny reamer.

    Anything I am rechambering a factory pipe I always recommend setting the barrel back enough to clean up the throat, leade and neck of the old chamber. This is where the vast majority of your accuracy potential comes from so I want everything freshly cut inthese areas.

    For the AI rounds you have to set the barrel back slightly to clean up the factory shoulder/neck junction. If you only set the barrel back the min needed, you will generally get a step in the chamber neck which a combination of the old loose neck and the new correct dimensioned neck.

    This another reason I recommend totally cleaning up the old chamber.

    Yes, you will loose a bit more barrel, generally 1/2" but there are also other benefits.

    First off, if you set the barrel back 1/2", you can rethread the factory barrel for that 1/2" which means you can get a much higher quality thread fit to the receiver.

    Also, generally, the custom chamber will still produce more velocity even if you use the same chambering because the throat and neck are much more quality which will not only aid in accuracy but also slightly higher velocity.

    To save the most barrel length and if your looking at wildcats, the 30-284 would be a very good choice as it would clean up the old chamber with no barrel set back except to clean up a very short section of factory chamber neck.

    All in all, this is all major surgery and you really need to remember that after all this machining and money spent, you will still be left with a factory barrel.

    Sometimes resutls can be dramatic if the barrel is quality and the accuracy robbing issues are with the machining.

    Other times there will be hardly any difference in accuracy at all because the problem is in the barrel itself. I tell my customers this going into every factory barrel rechambering and accurizing. Generally you will see a noticable difference but at time it can be very small.

    I do not particularily like spending my customers money on proceedures that will not provide known resullts. Hard for a customer to understand why the $400 he just dropped on his rifle only cut groups from 1 moa to 3/4 moa.

    For best results I would say shoot the barrel as is and use a neck sizing die to save your brass. Save up for a quality aftermarket barrel and when you get it have the rifle completely accurized. IT is a MUCH better investment for your money then trying to use the factory barrel.

    Good SHooting!!

    Kirby Allen(50)
     
  13. 4ked Horn

    4ked Horn Writers Guild

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    Thanks for your thoughtful response. I have, at this point, a gun that shoots better than I do so I'm not looking to really get a ton more accuracy. If anything I would bee looking to save on brass and maybe get some more velocity. With what you said though I'm sure I could buy quite a bit of brass and be content with my velocities for the money saved not reworking a factory BBL.

    So thats what I'll do. I'll save up for the better dies and go from there.

    One last question though. And it may be a quasi-stupid question. Since Al and I are essentially fire forming our brass to a fat chamber, and will soon be neck sizing, should we rework our max loads for the new case capacity to seek another "accuracy node"? Or is the slight expansion to a SAMMI spec chamber of little consequence in getting more useable velocity?