First time shoulder bumper

Discussion in 'Reloading' started by Nobody, Jan 20, 2011.

  1. Nobody

    Nobody Well-Known Member

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    Howdy everyone,

    Long time lurker, first time (I think) poster.

    Well, I went out and got one of those fancy rifles that have chambers so tight they require all sorts of voodoo magic to make 'em work right. It's built on a 260 Remington. I got myself some Sinclair bump gauges and according to what I've read, I need to fire a few rounds, then measure off the shoulders of the fired rounds with the bump gauge and then set up my die so that it bumps the shoulders back .002. I'm using Forster reloading dies by the way.

    So, I fired some rounds, and measured them with the bump gauge and got a reading of 1.555 +/- .001. I then ran them through the re-sizer and was only able to bump them to 1.554.

    The problem is, I've screwed the die body down so far that the shell holder, sitting on top of the ram, is contacting the bottom of the die. I'm still getting a fairly full length re-size (I always full length re-size), but the handle of the RCBS rockchucker is not going down as far as it used to. My question is, what do I do to insure the ram goes as far up as it should? I've been told that the bottom of the die needs to be ground off a bit. But how much? I have no tools to do this sort of thing which, I'm thinking, would require a machinist.

    Your wise and experienced answers are most appreciated.
     
  2. lamiglas

    lamiglas Well-Known Member

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    i am sure someone will chime in to answer your question, but i just wanted to add that i knock the primer out manually before i measure the fired headspace. this will ensure an accurate reading.

    you may have already done this, but i have found it to make a difference and thought it was worth mentioning.

    good luck
     

  3. Nobody

    Nobody Well-Known Member

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    That's a good point. I use an RCBS priming tool and it doesn't always seat the primers as deeply as I'd like. Not so much a problem with the 260, but seating primers for the 264 Win Mag can be...trying.

    Thanks.
     
  4. diriel

    diriel Well-Known Member

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    Take care with shoulder bumping sir, Sometimes less is more :) If I were you, I would run with what you can bump and see how it works. SD / ES will tell you a story about enough / not-enough bump. Also, of course, Neck Annealing. You probably already know that it is important to consistent ES/SD but I thought perhaps it might be worth tossing out there as well.

    Good Shooting sir,
    Gary
     
  5. Nobody

    Nobody Well-Known Member

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    Believe me, I'm a reluctant shoulder bumper. Despite having read up on it, I certainly do not consider myself an expert so no, I didn't know about the importance of annealing. I'd rather not have rifle that required bumping the shoulder but I learned about the tight chamber after I'd bought the rifle. I suppose though, it was inevitable since the cases get lengthened by repeated firings/re-sizings. I had some 264 rounds that were trimmed to length and then bullet seated off the ogives and they were still hard to chamber. A clear case for shoulder bumping I've been told.

    I'm beginning to think I should have started this thread by writing "I'm a shooter and I have a shoulder bumping problem.":)
     
    Last edited: Jan 20, 2011
  6. diriel

    diriel Well-Known Member

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    Does the current max bump you can do give you enough to chamber a round easily? If not, I would consider sending that stick in to a gunsmith who can open it up just a little bit. MOST reloading dies, when you FL resize, will put you at a happy spot where you could just go out and buy ammo if you ever needed to and shoot. If your dies will not resize enough to allow for this....I would say you are not in a happy place.

    Some times too tight really is!
    Gary
     
  7. fj40mojo

    fj40mojo Well-Known Member

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    Back your die out until you get full stroke with your press then begin screwing the die in in small incriments while sizing a lubed case. If you hold your hand up behind the die/shellholder contact area and look to see if there is any visible light ie space between the shell holder and the sizer when you are at the bottom of the stroke. You will feel the opperating mechanism "cam over", this is all the tolerance in the moving parts being taken up. If there still a sliver of light you can turn the die in a little more continueing with this process until you get zero gap between the two at full stroke on a case on it's first pass through the die. I reccomend you measure every time you make an adjustment. If at this point you are still only getting .001 bump then the die may need to have .001 turned off the bottom. Be careful, too much bump will generate an excessive headspace condition which will cause more problems. A .001 bump is probably OK but you may run into a chambering problem if your chamber is dirty or you don't get your primer seated properly.
     
  8. Nobody

    Nobody Well-Known Member

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    Wow, thanks a LOT for all your comments.
     
  9. Nobody

    Nobody Well-Known Member

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    There's one other question I should have probably asked, but which I aluded to earlier.

    The question is WHEN does it become necessary to bump a shoulder? If a case has been fired 1 or 2 times, should it normally require bumping? Or would you expect it to be necessary to bump shoulders of cases that have been fired 3, 4 or more times?

    Once again, thanks.
     
  10. diriel

    diriel Well-Known Member

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    The thing is, as brass is sized and re-sized over and over it work hardens and gets a certain amount of Spring Back. So both neck tension, and the shoulder both become inconsistent over time. This of course is very destructive to accuracy, but far too few people ever realize it.

    So it is really about taking care of "that end of the brass" as it were. When you Neck Anneal, you also anneal that part of the shoulder. The shoulder is the lesser of the two really, but it CAN be important. Hence Shoulder bumping. If you choose to shoulder bump, then you should do it every time. Other wise you are introducing an inconsistency into your reloading process. What fj40mojo said is dead on. Thing is, one to two thousandths is all you want! Less really is more, as he said, you want to avoid excessive Head Space issues introduced my excessive shoulder bump.

    Have a good one,
    Gary
     
  11. cowboy

    cowboy Well-Known Member

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    Let me add one more thing for consideration - Be sure of your shell holder - double check that it is the correct one and there is nothing lodged under it where it slides onto your rockchucker press. Assuming that it is the correct one and nothing forcing it up higher - then measure the thickness of said shell holder. I would then compare that thickness to a couple new ones at a sporting goods store after asking them permission - or do you have a buddy you could borrow a shell holder from and see how it compares to yours to try. With all the quality control junk that we are shipping in from China a couple thousands over thickness wouldn't surprise me in the least on a shell holder.

    With that said - before I would turn down the bottom side of an expensive die I would turn down my much less expensive shell holder. Any machine shop/gunsmith with a lathe should be able to do this in a matter of minutes - it's all set up time. You may get another .001-.002 by just polishing the top side of your shell holder also.

    I wish you good luck - isn't this a great relaxing hobby/sport.

    PS: What kind of dies do you have??
     
    Last edited: Jan 20, 2011
  12. Nobody

    Nobody Well-Known Member

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    Forster dies for the 260.

    Good point on shaving the shell holder instead of the bottom of the die.
     
  13. diriel

    diriel Well-Known Member

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    Nobody,

    Sir, you may want to consider that your head space is Too Tight! You should NOT have to be doing this! Serious. Get a set of Go-No-Go gages....check your head space.
     
  14. fj40mojo

    fj40mojo Well-Known Member

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    I agree with you Cowboy except if you are using that shell holder to load for multiple cartriges. This would pose no problem as long as you never reset the dies for the other calibers that you are using the shell holder with, but I sometimes take my dies completely apart and clean them. My preference would be to measure to the shoulder with appropriate tooling and set the die to bump the shoulder .002" which guarantees reliable feeding, an important attribute in hunting ammo to my way of thinking and if I were unable to accomplish that goal I would modify only the component that was out of spec. The shell holder for .260 is used for a lot of other cartridges, I'm using the same shell holder to load for at least 5 other cartridges, one could create more problems by modifying the common factor rather than the proble child.

    Tolerances are allowed in all manufactured goods, even dies and shell holders. What you may have is a condition of accumulated tolerance where the shell holder is at the high end of allowable tolerance for height and the die is at the low end of allowed tolerance for chamber dimension which results in the posters problem. I recently went through a similar albeit opposite situation where I set my die up to mfg's instructions and found myself bumping the shoulder back .014" and had excessive headspace. It is imperritive that we measure for ourselves and not trust the mfg to turn out product that works as advertised