neck sise and sholder bump

Discussion in 'Reloading' started by sodwyer, Oct 7, 2011.

  1. sodwyer

    sodwyer Active Member

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    I have switched to neck sizeing in all my bolt action rifles with great results. Just wondering is I should be full sizing after a number of fireings in order to bump the sholder back. I have had some cases that were siticky during retraction even at min load specs with cases properly trimed. What is the correct way to measure sholder bump? Is it manditory to use a FL die to bump sholder? Is there specail die set up when bumping scholder? ANY IDEAS? Thanks
     
  2. Mikecr

    Mikecr Well-Known Member

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    It's normal to reach a point where shoulder bumping is needed.
    You don't have to FL size cases for this, and can just bump as a seperate independent operation with a Redding 'body die'(unless it's an unusual wildcat).

    There are tools just for checking shoulder movement called headspace gages. These provide for a relative measure/datum on the shoulders, and you can use one to measure the difference between good chambering and bad chambering of brass. You set a body(bump) die & size until you achieve ~1-1.5thou under zero headspace. This should chamber well.
    You don't want to oversize this as excess headspace causes brass to stretch back against the boltface(increasing it's length and challenging the action integrity).
     

  3. Bart B

    Bart B Well-Known Member

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    The reloading industry calls tools that measure the head to shoulder distance a case gage; sometimes a case headspace gage. Headspace gages measure the rifle's chamber from the bolt face to the point in the chamber that stops the loaqded case from going too far forward. That chamber point is also where the case stops as the firing pin drives it forward and firing the primer.

    With such a gage, such as the RCBS Precision Mic, you can measure fired cases and set a full length sizing die to set their shoulders back 2 thousandths; about right for all bottleneck cases
     
  4. Gene

    Gene Well-Known Member

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    I like the Redding Instant Indicator for measuring bump. Have three of them. Unfortunately, they are caliber specific.
     
  5. sodwyer

    sodwyer Active Member

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    If I dont have any of those fancy tools will a full length size push the sholder back.
     
  6. Kevin Thomas

    Kevin Thomas Well-Known Member

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    Yes, but you won't know just how much. Invest in one of the gages, even one of the cheaper ones, and you'll be ahead of the curve. Need to know what you're moving here, and the only way to do that is to measure it. That's where the gages come in.
     
  7. Bart B

    Bart B Well-Known Member

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    Kevin's absolutely right on this one.

    The reason is, depending on how much case lube's on the fired case and the difference in diameters of the fired case and die, you can easily have a spread across two dozen cases of 3 to 6 thousandths of shoulder set back. Good case cleaning and lubing processes can get the spread down to under 3 thousandths.

    When you get the case gage, use it to full length size your cases such that the ones with the highest sized case headspace reading is about 2 thousandths shorter than the average reading you get from measuring several fired cases. This insures that all your cases will chamber easily. And even the ones that had their shoulders set back the most will still be safe in your rifle.
     
  8. CRNA

    CRNA Well-Known Member

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    +1. I use the Hornady headspace gage. The thing is, it's almost impossible to see 0.002" with the naked eye, so you have to have a gage to tell you when you have set the shoulder back that far.
     
  9. Bart B

    Bart B Well-Known Member

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    While I've never used them, there are shell holders one can get that vary in height in 2 thousandths increments. Couple of people have told me one can set their full length sizing die to just bump the shellholder against the bottom of the die which gives very uniform sized case headspace. With such a shellholder properly sized for your die and rifle chamber, very consistant sized headspace is guaranteed, so they say.
     
  10. Mikecr

    Mikecr Well-Known Member

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    Anyone who measures their HS knows that sizing alone can not be relied on for it's consistancy.
    It has to be measured/verified -every single one. Otherwise your headspace is all over the place.

    I can change the HS +/- 1thou with lube, and it can't be predicted because what sizing leaves is also greatly dependent on the brass hardness, designed angles, and amount of bump.
    FL sizing only adds to this abstract, due to brass rolled up the case with each sizing.

    Now you can squash the livin hell out of brass to the point where HS inconsistencies mean little more than increased ES, shortened brass life, and degraded performance(due to effective seating). But I don't and wouldn't recommend it.
     
  11. sodwyer

    sodwyer Active Member

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    Sounds like I will have to spend a little cash. I did fL size about 15 cases wich totally solved my sticky bolt problem however I have know idea how far the sholder moved this resulted in a high ES and low volocities. Im wondering if I go back to the neck sizer on these brass if my load will come back.
     
  12. Reloader222

    Reloader222 Well-Known Member

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    I have found that 2 out of 10 reloaded cases would not chamber well in my .222 Rem. They were all sized in the same dies set. Hower some cases were from my own gun and others from my dad's. The only reason that I can think of is that the sizing of those cases which was fired in my gun, was sized sufficiently, but those from my dad's gun had probably needed the shoulders to be bumped back a little more. The cases are all Sako. From now on I would take a case that is difficult to chamber and then bump the shoulder back sufficient until it chambers well and keep that setting for all the cases. I do use the tool that fit on the vernier to measure the cases on the shoulder and must say that without that it is impossible to do it correctly. With this tool you also prevent the over-doing of the shoulder bumping, because too much bumping of the shoulder could cause headspace problems and also cause inaccurate groupings.