Head Spacing, FL Sizing Die, Shoulder Bump

[16tpi]

Okay I have been reloading for years, maybe someone has noticed this before or maybe not. If you are bumping your shoulder on your brass, the question is WHY? I have been looking to find the answer. In my line of work as an A Tool & Die Maker you have to give dies clearance to form the material the dies are forming. If it doesn't have the correct clearance the die will rip the material or leave it looking like a pie pan wrinkled up.

Now I have taken the time to setup my press to find out the why. I'm guilty of bumping the shoulder on my brass. I have a shell holder that will let me bump the shoulder back.

TEST

I set my die up using a standard shell holder, 0.125 of an inch from where the brass sits on the holder to where the holder bumps the die. Setup an indicator on top of the die and Zero it, to see what i am reading when i bump my brass with the bump that is required to get a smooth bolt closure. I put my bump shell holder in, and set the die to where i size the brass normally, -0.0105 of and inch is the reading i get when I size a brass. Now with that being said I use my GO GAUGE to see how far the die is set from there, the reading i get is -0.009 of an inch on the GO GAUGE.
Now the math says I am bumping my brass a total of -0.0015 of an inch.

So if the head spacing is where the cause of need to bump the shoulder is, why not add .0015 to the back of the head space gauge?

If it is the die, why not take it off the bottom of the die?





Your thoughts???

 

[Dusty Stevens]

.001 is a perfect bump in a match rifle. The only reason to fl size and bump is to put your brass back where it was and like you know to get smooth bolt closure. If you change your headspace no matter where it goes you need to bump at least .001 to get the best bolt closure. If you go too far then you gotta modify the die. Theyre made to be able to bump when your chamber is set to the specs of your chamber and gages. For example if your chamber is zero headspace and your die bumps .001 hitting that particular shellholder, if you run the reamer in .002 farther then you wont be able to bump your shoulder or fully resize your brass. You get the picture im sure- you may be taking your knowledge and overthinking it- or i dont see what youre getting at- one of the 2!

 

[dkhunt14]

Another thing is brass gets harder from firing and sizing. As it gets harder you get more spring back. What works for the setup today might not work 3 firings down the line. I measured my bump a few years ago, I set the die up to bump a .001. It was bumping them ok. Then I annealed them and now my bump is .005. Maybe like Dusty said, I don't understand what you are trying to say. Matt

 

[LHSmith]

If it doesn't have the correct clearance the die will rip the material or leave it looking like a pie pan wrinkled up.



If it is the die, why not take it off the bottom of the die?





Your thoughts???

The neck and shoulder are annealed.....this prevents the die from distorting the brass.
If you're thinking is to have a perfect line-to-line fit where headspace (gap between chambered case shoulder and chamber) is -0- then you are getting into the interference fit area where every 0.0001" variation will result in harder bolt closure. This will lead to accelerated wear on bolt lugs and abutments and accuracy degrading upset of the rifle in the rest.

 

[Patch700]

One exaggerated way of putting is this... If you had a semi hardened piece of modeling clay and ran it through your setup and then ran a piece of over worked brass into the same setup would you achieve the same dimensions?? I think you see where this is going.

 

[fguffey]

So if the head spacing is where the cause of need to bump the shoulder is, why not take .0015 off the back of the head space gauge?

My dies and presses have threads. Threads facilitate adjusting the die to, off or below the top of the shell holder. I have an advantage, my cases do not have head space, and my cases have a length that is measured from the datum/shoulder to the case head. I off set the length of the chamber from the datum/shoulder to the bolt face with the length of the case (from the shoulder of the case to the case head).


Another advantage I have when sizing a case; I find it impossible to bump the shoulder. When I size a case the shoulder does not move, I have fired cases in chambers with .127” clearance between the case shoulder and chamber shoulder with out case head separation; again, the shoulder on the case with .127” clearance never moved.


Another advantage; I can check the length of the chamber (head space) three different ways without a head space gage. Every tool is not a head space gage and everything does not have head space.


Back to bump; I have presses that are bump presses. All of my bump presses are cam over presses. I have presses that do not bump, if my press bumps it bumps twice; the ram bumps once on the way up and once on the ram down. If my press does not bump/cam over it is a leaver lock. My leaver-lock presses lock up, jam up or it goes into a bind. When the linkage on my non cam over presses gets tangled up the ram is kicked forward at the top and kicked back at the bottom because the linkage limits the travel.


F. Guffey

 

[16tpi]

My thoughts,
A FL Die is suppose to size the brass fully? yes, if this is the case, why are we having to bump the shoulder? Because the die is not doing its job all the way. I feel that the extra step in bumping the shoulder is a job for the fl die. The die is smaller than the case in every aspect, except for the shoulder. So when making the die, why not bring the shoulder area back to bump the brass in the same stroke it takes to form the rest of the brass with no other extra shell holders. In turn making the die do what it is suppose to do.

Or when chambering, short chamber the head space by -0.001 or -.0015, to keep the brass from blowing out past the nominal size? By doing either of the two would stop the need of a shoulder bump.

The brass case is not going to grow any bigger than the chamber actually is, the reason behind this is the brass has a spring back. As all metals do when forming or shaping. if you make the chamber longer the brass is going to be longer. If you set the headspace to loose with a GO GAUGE the brass is going to grow within the chamber, in turn making the need to bump the shoulder of the brass.

 

[Sheldon N]

While I generally agree with the consensus math that you want to bump the shoulder between .001 and .002 for consistent chambering effort and consistent size, I think the more important assessment is bolt feel.

Pull the firing pin out of your bolt along with the ejector spring so that the bolt opens/closes with no effort. Clip a fired piece of brass under the extractor then chamber it... feel the resistance of the brass case against the chamber. For me a fired unsized case has a moderate amount of resistance to chambering.

Now slowly adjust your full length sizing die, sizing the brass .001 at a time, until the bolt closes on the brass with just a hint of resistance (or right when it hits no resistance if you prefer). Double check on a few other fired cases to make sure it's consistent.

I bet your bump will be around .002, but this way you've set it exactly correct so that you can cycle the bolt with minimal effort and won't be disturbing the gun between shots, and you won't be sizing the brass anymore than necessary.

 

[dkhunt14]

My thoughts,
A FL Die is suppose to size the brass fully? yes, if this is the case, why are we having to bump the shoulder? Because the die is not doing its job all the way. I feel that the extra step in bumping the shoulder is a job for the fl die. The die is smaller than the case in every aspect, except for the shoulder. So when making the die, why not bring the shoulder area back to bump the brass in the same stroke it takes to form the rest of the brass with no other extra shell holders. In turn making the die do what it is suppose to do.

Or when chambering, short chamber the head space by -0.001 or -.0015, to keep the brass from blowing out past the nominal size? By doing either of the two would stop the need of a shoulder bump.

The brass case is not going to grow any bigger than the chamber actually is, the reason behind this is the brass has a spring back. As all metals do when forming or shaping. if you make the chamber longer the brass is going to be longer. If you set the headspace to loose with a GO GAUGE the brass is going to grow within the chamber, in turn making the need to bump the shoulder of the brass.

A chamber actually expands like brass. That's why they can measure pressure with a strain gauge. If you are shooting moderate loads the chamber expands with the brass and they both spring back. Now the dimensions between the two are close. When match shooting you need to have the cases chamber and extract easily so it doesn't upset the gun. Matt

 

[BoydAllen]

The point of FL sizing is to create a controlled amount of clearance between the chamber and loaded case. If you shoot a piece of brass several times only neck sizing it, at a pressure that takes full advantage of the potential of the cartridge's design, it will become undesirably tight in the chamber. Rifle chambers are not all set to exactly the same headspace, there is some allowable tolerance. that is the reason that dies need to be adjusted for each rifle. Also, as brass is repeatedly fired and FL sized it becomes work hardened increasing its spring back. Because of this a die setting that bumps the shoulder of a case that has been fired only a few times, will not bump the shoulder of a well used one that is harder and springier. A lot of problems in this sport come from excessive use of "it make sense that" and not enough careful testing and measuring. Lastly, ones ability to properly set a die by feel depends on the die's dimensions being correct for a particular chamber. It may not be, and there is no way to really know what someone has when answering a question on the internet, which is why I object to the common practice of telling shooters to use bolt feel to set a FL die. Use the proper tool to measure shoulder bump, and if that setting does not give the bolt feel that you are looking for, you need another die.

 

[Patch700]

A possible case in point to what Boyd touched on would be one occasion where a friend came over to do some shooting at my place.
He is an experienced reloader/shooter and brought over one of his varmint rigs where he wanted to confirm a few things.

Because i am setup to load in the field he too decided to do his own loading out there as well. I informed him to bring a bunch of precharged powder dumps in test tubes and we wouldn't need to setup scales.

During the resizing process he noticed his bolt becoming slightly snug on closing on some rounds and blindly decided to adjust his die to accommodate.. He did not verify by measuring and merely went by "feel".
I asked him to verify his numbers for a joke and what he found was that the cases that were showing slight drag and were resized to have a certain "feel" were now .003" shorter than the other cases that felt fine..
He was needlessly bumping shoulders when the actual problem was a slight need of sizing in the back end to achieve the feel he was looking for. However this didnt happen untill he adjusted his die to accomodate that.

 

[16tpi]

So it is impossible to have a die that already has the amount of bump it takes to make a brass feel as if it was off the shelf, or near close but precision.....

We have been bumping shoulders for years, if its not broke don't fix it kind of thing. I think it would be very nice to walk up to any press and have a die to be set it run the brass thru it and be done. No matter what shell holder or the amount of bump the die is going to put on the brass. There are a lot of Guys out there that are bumping there shoulders... every chamber is different, yes. But that is the reason for SAAMI Sporting Arms and Ammunition Manufacturers' Institute, they set a standard to runn a production ammo. Do Lapua bump there shoulder on new brass? Fired brass or not you should be able to run it thru a die and form it back the way it was before firing. Anneal if need be. So is it a standard to bump shoulders when reloading, STBSWR, sounds like somethings been transmitted. LOL But on a serious not I use Lapua or Norma brass both are different and both work very well for my app. I use a single stage camover press, Comp Redding dies, with carbide bushing and sizing ball are in .0001 sizes. That is the joy of an Wire EDM machine. And I measure with either Starrett or Brown and Sharp tools. I feel there is on need for a central tool to be on my precision bench. I have seen Wilson dies used first hand . ill pass.....

After measuring the shoulder I am getting -0.0015 to -0.002 depending on the brand of brass i check. I have also noticed that running a 40 degree shoulder before bumping it back, it is nice a sharp edge at the intersection of the case body taper to the shoulder start. After it is slightly radiused edge, almost as if the shoulder taper isnt moving more of the wall is about to crush. All I know is it works and well.

Every good thoughts on the subject.

 

[Sheldon N]

When match shooting you need to have the cases chamber and extract easily so it doesn't upset the gun. Matt

Like Matt said, this is the most important thing.

Now as Boyd pointed out, there's the potential that the FL sizing die doesn't match the chamber perfectly and that you get a tiny bit more shoulder headspace than you want at the correct bolt closure "feel". Your only options at that point are to try a bunch of other FL sizing dies to see which one matches your chamber, or to have a custom die built. That would be too much effort for me personally, and I'd just live with the slight variation in measured numbers once I had the correct bolt feel.

Other thing to consider is that a comparator tool can possibly give you readings that don't perfectly match up with how the case is indexing inside the chamber, especially on shallow shoulder cases like a 308. You might need a chamber gauge cut with the same reamer as your rifle to be sure exactly how much shoulder bump relative to your chamber you are getting.

 

[16tpi]

A possible case in point to what Boyd touched on would be one occasion where a friend came over to do some shooting at my place.
He is an experienced reloader/shooter and brought over one of his varmint rigs where he wanted to confirm a few things.

Because i am setup to load in the field he too decided to do his own loading out there as well. I informed him to bring a bunch of precharged powder dumps in test tubes and we wouldn't need to setup scales.

During the resizing process he noticed his bolt becoming slightly snug on closing on some rounds and blindly decided to adjust his die to accommodate.. He did not verify by measuring and merely went by "feel".
I asked him to verify his numbers for a joke and what he found was that the cases that were showing slight drag and were resized to have a certain "feel" were now .003" shorter than the other cases that felt fine..
He was needlessly bumping shoulders when the actual problem was a slight need of sizing in the back end to achieve the feel he was looking for. However this didnt happen untill he adjusted his die to accomodate that.

I like this one the most it shows the effort of transport die to a new setup and try to run brass thru it. If you do it by feel it will not be the same, my feel and yours are to different. as in presses they are not the same on could have more or less leverage than the other. but feel the same. measure is best. To setup i use an indicator on top of my press std shell holder and bump the holder. Watch the needle to know when all the movement is out. at this point ZERO out the indicator. After the shell holder touches and the press cams over the job is finished with that shell holder. now insert the bump shell holder and move the amount it takes to get a nice smooth bolt closure. At this point WRITE IT DOWN for a future note.

That is what would be nice to say hey man i got the baggage today just bring your dies and we will shoot till the barrels get hot and reload and let them cool.

 

[16tpi]

Like Matt said, this is the most important thing.

Now as Boyd pointed out, there's the potential that the FL sizing die doesn't match the chamber perfectly and that you get a tiny bit more shoulder headspace than you want at the correct bolt closure "feel". Your only options at that point are to try a bunch of other FL sizing dies to see which one matches your chamber, or to have a custom die built. That would be too much effort for me personally, and I'd just live with the slight variation in measured numbers once I had the correct bolt feel.

Other thing to consider is that a comparator tool can possibly give you readings that don't perfectly match up with how the case is indexing inside the chamber, especially on shallow shoulder cases like a 308. You might need a chamber gauge cut with the same reamer as your rifle to be sure exactly how much shoulder bump relative to your chamber you are getting.

How do you know the feel that you are feeling is body or shoulder, could be either from different press. Yes i do see what Boyd is saying.

I think all of you have made some really good points.

 

[LHSmith]

How do you know the feel that you are feeling is body or shoulder, could be either from different press. Yes i do see what Boyd is saying.

I think all of you have made some really good points.

Bolt lift hard on close - hitting on shoulder .....bolt lift hard open- case web (body) not sized enough (along with "click")

 

[BoydAllen]

Typically new brass is smaller in diameter and head to shoulder than most any FL die would produce. I have seen rimless cases that were .006 under fired. With belted .021 is not uncommon. I can think of no reason to want to return a case to its unfired dimensions. There is a thing called an incipient separation, which will progress to a separated head. I have used my Stoney Point (now Hornady) "Headspace Gauge" for years, on cases with as little shoulder angle as the .220 Swift with no issues. IMO careful measurement is the key. Some years back, when I suggested that a friend might want to measure instead of going by feel, he gave me the old "(I've been loading for years...yada yada", at which point I challenged him to set up the same die, starting from scratch, by feel, several times, and bring over the sized cases, along with a tight fired case for measurement. He did, and his die settings were all over the place. To his credit, he went home and made a suitable gauge using his lathe. I loaded for some time before I learned how to do it much better and more precisely. The key was getting the tools to take proper measurements with, and paying more attention to what I was doing. To a degree, a lot of what we do in the pursuit of fine accuracy is not necessary to reload for most hunting and recreational shooting. I know this. But I would rather teach someone how to do a thing to the highest standard that I can, and leave "good enough" for others.

 

[Sheldon N]

Yes, absolutely agree that measurements should be a part of any sizing process. I use a calipers and comparator when sizing and get the correct bolt closure "feel" at around .002 shoulder bump.

 

[DanSavage]

I don't really under stand this,, I've been reloading and shooting match's for years and have several brands of dies.

I think the OP must have a die that is cut too deep?

In the beginning I used a Lee full length sizing die with no special shell holders. I would set that die to size the case just enough where the bolt would close with a hint of resistance at the end of bolt closer. I would measure the head space at the datum line and confirm around -.002"
What more is to be desired?

Now days I set the head space of my barrel to brand new Lapua brass. I use a Redding body die in which I set to reduce the brass -.001" in every dimension except the head, extractor groove and neck (naturally). Then I run the case into a L.E. Wilson neck die.

I don't see how you could possibly get any better than that,, though they make dies to do what I do accomplished in one step,, the full length bushing dies.

In some chamber's the base area may be a little over sized requiring a small base sizing die.

 

[LHSmith]

I don't really under stand this,, I've been reloading and shooting match's for years and have several brands of dies.

I think the OP must have a die that is cut too deep?

It's unclear to me also. He seems to want to share a press in the field that guarantees precise shoulder set-back from one die to another? I don't believe he grasps the fact that not every piece of brass workhardens at the same rate- no matter if from the same lot, fired and sized the same # of times with the same loads. ....or that variations in shoulder set-back affects accuracy adversely.