shouder bumping

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Jeff Flannery

Jeff Flannery

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All.. I've been reloading a LONG time and just now am starting to get into more accurate loading. How do I bump the shoulder back on my bottleneck cases for minimum headspace? Do I use the full length die or neck sizer? Thanks!!
 
You use a FL sizer or body die. if you use a body die you can use a neck sizer to set the necks or the use of Bushing die.
What you need to do is measure what the shoulder position is prior to sizing. Then you only need to move it back 0.001"-0.002"max. If for a simi-auto you need to go back to saami spec. This is easily done with the use of a case gauge or 0.002-0.003" provide your not extraction the rounds under high pressure. This is why a case gauge is handy for a simi-auto (AR's etc).

There are several ways to measure the shoulder position. From real expensive to virtually no cost. Most use the Hornady gauge. It can be done with a piece of pistol brass too. Just need to fine what size fits over the neck and contact the shoulder, in the mid way area preferred. Then you measure before and after sizing to see where your at and make the necessary corrections. On the High end is the RCBS Precision Mic. This is pretty useful if your loading for more than gun.
 
Either buy the Hornady headspace comparator or one from another company and just turn the FL die in enough to knock it back 2-3k. I do this with an RCBS FL die i don't think a neck die effects the shoulders so use a FL die and just keep adjusting until the desired length is met.
 
Full length sizer. Get someway to measure shoulder position before (fired) and after (sized).
 
What I do is use a Wilson case headspace gauge (sometimes wrongly referred to as a case gauge). Take a case fired from your gun, and measure how much it protrudes from the head end of the gauge. Keep adjusting the sizing die and check with the headspace gauge until you get the desired bump. I use a dial gauge, but you can use your calipers. Use a regular FL sizing die, or a body die along with a neck sizing die.
 
Thanks for the feedback, guys! I have the hornady comparator (or however its spelled) I've STUDIED videos and such and understand head space finally. I didn't know if the neck sizer moved the shoulder back or not. Can I safely full length size every time I reload? I usually neck size only for my bolt actions. Eventually the bolt is hard to close and I finally think I know why!!! Will full length sizing every time shorten brass life or can I neck size until the case gets hard to chamber? If I measure fire formed cases that chamber in my gun(s), then record the length with the comparator, record that, then that should be my chamber size, correct?
 
Jeff Flannery said:
Thanks for the feedback, guys! I have the hornady comparator (or however its spelled) I've STUDIED videos and such and understand head space finally. I didn't know if the neck sizer moved the shoulder back or not. Can I safely full length size every time I reload? I usually neck size only for my bolt actions. Eventually the bolt is hard to close and I finally think I know why!!! Will full length sizing every time shorten brass life or can I neck size until the case gets hard to chamber? If I measure fire formed cases that chamber in my gun(s), then record the length with the comparator, record that, then that should be my chamber size, correct?
Click to expand...
Full length sizing will shorten brass life cause its working it all IMO. Take a piece of brass you fired in your bolt gun and measure it with the comparator then turn the FL die out and lightly keep sizing it until the shoulder of the case measures 2-3k smaller than the first measurement. Your bolts getting hard because the shoulder is moved forward too much so it needs knocked back.

Say a fired case that's not been sized measures 133 with the comparator you need to adjust the die to make it measure 130 now and that's 3k bumped back.
 
Also
Toprudder said:
What I do is use a Wilson case headspace gauge (sometimes wrongly referred to as a case gauge). Take a case fired from your gun, and measure how much it protrudes from the head end of the gauge. Keep adjusting the sizing die and check with the headspace gauge until you get the desired bump.
Click to expand...
Interesting. I'll keep this in mind. thanks
 
If your neck sizing you only need to do a minimal setback, 0.001". As it is your probably getting 3-4 firing before needing to bump the shoulder. This is important if you have a over size chamber to get the most life out of the brass as you can. The less you move the shoulder the less work hardening that is done. If you have a way to anneal, you extend the brass greatly. I have 223 brass with over 10 firings and still going strong. I have a annealing machine so I run them through every time as part of my brass prep. Since these are not hot loads the primer pockets are still good. The hotter you push them the shorter the life.

As for a simi-auto you have to push the shoulders back 0.002-0.003 for reliable feeding. Not all chamber are the same, some are minimal spec match chamber while some are very loose chambers. I've helped neighbors setup for chambers that were out of spec, long. If you were to set back to SAAMI spec every time the brass fails after 3 firings. Moving it back only enough to ensure chambering he has double the life of the brass.

I always shoot for the least amount of setback, for maximum brass life.

Some of the cartridge gauges have slots cut in them (LE Wilson) for min and max. So you shoot for the center. The Wilson can also tell you if the brass needs trimming, if you flip it over and have the head setting flat on table. The proper way to check is to run a straight edge across the top. If it hangs you will know. I can not detect very small changes by using touch.
 
The average human index finger can feel the difference of three thousandths of an inch, in a flat plane. That will put one over the minimum sizing that they were shooting for.

Plethora of Useless Information Man, AWAY!
 
Jeff Flannery said:
Can I safely full length size every time I reload? I usually neck size only for my bolt actions. Eventually the bolt is hard to close and I finally think I know why!!! Will full length sizing every time shorten brass life or can I neck size until the case gets hard to chamber? If I measure fire formed cases that chamber in my gun(s), then record the length with the comparator, record that, then that should be my chamber size, correct?
Click to expand...
Full length sizing will not appreciably shorten case life if you don't move shoulders too far.

Measuring a fired case doesn't really give us our chamber since brass springs back some, but it does give us a starting point for setting up our sizer.

I set up my .223 sizer with my Wilson case (Headspace) gauge, making sure the cases fell between the cut (Min/Max) like Blue68f100 posted. I set up my 300 BLK sizer to move the shoulder an average .003. Cases from both calibers last until the primer pockets get loose.
 
1KPerDay said:
Don't think Demi human was being rude. He was referring to himself as the plethora of useless information man. Pretty sure I can feel a couple thousandths of rim protruding past the end of my Wilson gauges.
Click to expand...
Re read it 3 times guess I was wrong and apologize :)
 
I feel one of the primary benefits to full length sizing is consistancy every cycle. Every time I load it is the same process. I full length resize everytime and only lose brass when it comes flying out of my AR to parts unknown.

Beside inopertune recollection of random data, my other super powers include sitting motionless at a bench, baking cookies with my kids and corny humor.:oops::)
 
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