Bumping the shoulder

billbmcleod

billbmcleod

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I was reading a blog about bumping the shoulder on bottleneck cartridges and had an idea of just slipping a .002" piece of shim stock under the case head in the shell holder. I tried it on a .308 case and it seemed to work but I don't have a rifle that is tight with the brass the way it was to see if I made a difference. It might save someone from buying a set of competition shell holders or a different sizing die if a couple of thou was all that was needed.
Does this seem reasonable?
Or is this a common practice for some?
 
I did exactly that, sliding various thicknesses of feeler gauge under the brass head, in the shell holder - to gain three or four thou more into the die, to see if that was going to make a difference on what I was doing - turned out to not be the answer, so was a ton cheaper experiment than buying various height shell holders or to grind the top off of existing shell holder or bottom of that die. I am assuming that bottom of your die was already tight against the shell holder, and you wanted a smidgeon more sizing??
 
What reason are you loading for and want a shoulder bump?
You really need to know your fired case length to the shoulder before you can start bumping shoulders.
 
Why not just turn your sizing die down 0.002" ?
Or has it bottomed out? If bottomed out for a short cartridge, maybe you need an extended height shell holder? Then you will have all the adjustment in the die you need?
 
Back in the day I had a 300 WM that the only way we could get previously shot brass to chamber was to stick a piece of paper under the head in the shell holder. Very little, also, to work off
 
I may be understanding you wrong?
Bumping the shoulder back .002" is NOT using your full length sizing dies too its maximum , then squeezing it another .002" smaller.
The idea of bumping the shoulder back is a brass fired in your gun, so it is now sized to your gun's chamber, and then bumped back .002".
Not Full length sized minus .002"
It is brass that the shoulder is set back from the point in the chamber where the cartridge headspaces the amount of .002".
 
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Post #7 got me to thinking - maybe not good... I do know that Full Length sizing with die set much too high and working down - like when partial sizing, ends up squishing case walls in slightly, and at some point, pushes the shoulder forward. Now a previously fired case will no longer chamber - marks are on the shoulder - that is what is stopping bolt from closing. Continue to lower the die and eventually it does chamber - but almost always the neck got slightly longer - I had always assumed that is where the brass got squished to. So "shoulder bump" - does that work the opposite way? Setting back the shoulder from the fired condition, without side wall support, can push back shoulder but make case "fatter" - would then feel "tight to chamber", but marks would be on walls, not on shoulder? I have never used a "shoulder bump" die, as you probably can tell by my question...
 
I always set my die touching the shell holder and I have never had a problem with my guns or brass. My post and question was for information and interest should I have a problem. If I do have a problem now there is more than one solution to try. Whichever one works first is the best.
Thanks to all for your response.

Bill
 
What I usually do when setting up for a new rifle is to "stretch" the shoulders of a few cases forward by purposely setting the die higher.

If they're long enough they'll chamber hard or not at all. Then I slowly lower the die in small increments until they just chamber easily and then lock the die nut. For hunting loads, I'd recommend that you try each case in the rifle it's intended for before loading. Surprises when it comes to shooting aren't usually good, but some situations are worse than others.

This is for a bolt action, I'm told you should have more shoulder bump in a semi- auto or other action.

Hardness of the brass plays a role also. The shoulder will spring back to some degree, more so in harder brass. I anneal my cases at each firing, so their relative hardness is the same.
 
To really know how much you are "bumping" the shoulder back, you must know the distance from the
head of the case to the datum line on the case shoulder. Then you can determine how much you are
bumping the shoulder back. My target in hunting rifles is .0015" .002" is OK for semi-autos and
other, non-bolt actions. Keep in mind that if you bump the shoulder back excessively, you will have a
case head separation. Dave.
 
billbmcleod said:
I was reading a blog about bumping the shoulder on bottleneck cartridges and had an idea of just slipping a .002" piece of shim stock under the case head in the shell holder. I tried it on a .308 case and it seemed to work but I don't have a rifle that is tight with the brass the way it was to see if I made a difference. It might save someone from buying a set of competition shell holders or a different sizing die if a couple of thou was all that was needed.
Does this seem reasonable?
Or is this a common practice for some?
Click to expand...

Issues that might come up... variations in the extractor groove, removing slop in the shellholder forcing case to not self align in the die, dealing with a shim that may fall out.

I prefer to work from the top down...

Potashminer, a body die is pretty much a FL sizing die without the expander bits. In general, it should be slightly larger in the case body taper/dimensions but haven't compared to every other FL sizing die in my chambers. so when you bump the shoulder, the rest of the case is also supported stopping any brass flow into areas you don't want.

What I can say with certainty is the base area of my body sized cases are not squished which is ideal for alignment in the chamber. I have had FL sizers squish this area which is great in a working rifle but not so much for peak precision.

I am sure an enterprising person with a lathe could polish a FL sizer to do the same thing...

Jerry
 
I didn’t think there would be any intentional dimensional/sizing difference between say a Redding FL sizing die and a body die. For times when I couldn’t find a body die in stock anywhere I sprung for the FL bushing die thinking I was just spending more for the same thing essentially.

Mystic Precision said:
Issues that might come up... variations in the extractor groove, removing slop in the shellholder forcing case to not self align in the die, dealing with a shim that may fall out.

I prefer to work from the top down...

Potashminer, a body die is pretty much a FL sizing die without the expander bits. In general, it should be slightly larger in the case body taper/dimensions but haven't compared to every other FL sizing die in my chambers. so when you bump the shoulder, the rest of the case is also supported stopping any brass flow into areas you don't want.

What I can say with certainty is the base area of my body sized cases are not squished which is ideal for alignment in the chamber. I have had FL sizers squish this area which is great in a working rifle but not so much for peak precision.

I am sure an enterprising person with a lathe could polish a FL sizer to do the same thing...

Jerry
Click to expand...
 
Mystic Precision said:
Issues that might come up... variations in the extractor groove, removing slop in the shellholder forcing case to not self align in the die, dealing with a shim that may fall out.

I prefer to work from the top down...

Potashminer, a body die is pretty much a FL sizing die without the expander bits. In general, it should be slightly larger in the case body taper/dimensions but haven't compared to every other FL sizing die in my chambers. so when you bump the shoulder, the rest of the case is also supported stopping any brass flow into areas you don't want.

What I can say with certainty is the base area of my body sized cases are not squished which is ideal for alignment in the chamber. I have had FL sizers squish this area which is great in a working rifle but not so much for peak precision.

I am sure an enterprising person with a lathe could polish a FL sizer to do the same thing...

Jerry
Click to expand...

Thanks for the explanation, Jerry - see - I know something now, that I did not know this morning - and it did not cost me dollars, or skin and blood on the floor - so made the day worth it!!! (The stuff on the floor and up the wall is from some other learning today, on the lathe, and today's dollars were only VISA dollars, so a few days before that bill shows up!!!)
 
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Chargerguy said:
I didn’t think there would be any intentional dimensional/sizing difference between say a Redding FL sizing die and a body die. For times when I couldn’t find a body die in stock anywhere I sprung for the FL bushing die thinking I was just spending more for the same thing essentially.
Click to expand...

SAAMI allows some possible variations... so I can't say what you will get out of the box. In general, you are more then likely correct but look at Lee which tends to lean on min spec and I just dont bother guessing anymore... measure and use what works best for the tasks and platform.

Jerry
 
I continuosly read posts about to bump or not bump the shoulder.

I shoot SR BR and I know what we do in our circles. That is every time we reload our 6PPC or even 30BR brass we use the proper fitting dies. We bump the shoulder, neck size and squeeze the case every time. This gives the BEST brass life.

Tell me, do you not think that just neck sizing and bumping the shoulder back when required the brass is not getting harder/ memory in doing that?

We know what happens after continual sizing to the same dimension every time. Eventually it is not enough and you have to squeeze it more. By that time the brass is done.

I just do not get why so many say I only bump the shoulder when it gets tight.

So much different info than is used in the BR world. It is not because it is the BR world but that is the same for every cartridge.
 
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