Why can't I measure shoulder bump?

[divingin]

One thing that I feel contributes greatly to inconsistency in sizing is press stretch. Or rather press stretch and case lube.

As you stuff a case into the sizing die, the force causes the press frame to stretch (this is why the manufacturers say to screw the die in to touch the shellplate, lower the ram, and screw in a bit more. This assures contact at the top of the ram stroke, which we've already determined can be a bad idea depending on your setup.) If you are trying to size to specific amount of setback (rather than the max amount possible, as would happen with full contact between die and shellplate), and your cases exhibit differing resistance to sizing (I'll use inconsistent lube as the cause, as you can't do much about cases that are blown out differently), the amount of stretch the press exhibits will change, and so will your results.

If you do have cases that are fired to substantially different body diameters, it may help to approach your final measurements in one step, relube and set the final dimension in a second sizing. You'll have more consistent force on the press when trying to fine tune the brass.

 

[6MMsteve]

Here are the facts. Camming over is the ONLY way to get consistent shoulder bump...and no, it doesn’t ‘stress’ the linkage, it’s designed to do this.
When Partial FL sizing, aka shoulder bumping, with the brass all the way up in the die, if there is a gap between the bottom of the die and shell holder, then FL sizing is NOT happening.
Just because the die touches the shell holder without the brass present means diddly squat. The brass resists the sizing and without cam over the linkage WILL NOT overcome this due to the linkage slack.
If you have a press that doesn’t cam over, like a Lee, then you need to use a feeler gauge under the case head in the shell holder. A .010” normally overcomes most issues.
With a cam over press, once touching, screw the die IN 1/12 turn, size a case, measure and repeat until you get the desired bump.

Cheers.

I never cam over and get very good bumpin or readings on my peterson 6xc brass no more than .0002 diff actually I have never cammmmed a press...but my headspace is set tight always

 

[6MMsteve]

Never understood camming over. Doesn't make sense to me. You can only shove the case so far into the die?

never have cammed one myself..maybe I'm missin sumthin

 

[BoydAllen]

Not to hijack the thread, but I thought this might be of interest and importance to those here.
In regards to cam over, I had a discussion with the engineer from Redding (he was that week’s guest) on The handloader podcast. He flat out told me that the T-7 press was designed expressively for cam over use. That put my mind to ease, because I always felt I was damaging the press by camming over.

There is cam over, and then there is CAM OVER. I would say that the latter really gets you nothing more than the former. Back in my neanderthal years, I actually mushroomed the bottom of the sliding piece of a collet die with my rock chucker. I remind my self of those kinds of mistakes from time to time when I am helping beginners. The first thing that I teach them about setting up a FL die is to ignore any mfg. instruction that tells them to screw it down untill it touches the shell holder and then lower the ram and turn it an additional quarter turn. I have even seen this jackassery on YouTube. A little cam over will make bump more uniform if you can get there with the correct bump. If you have more than that IMO it is time to do a little work on the shell holder.

 

[skeeljc]

If you are sizing with a gap between the shell holder and the die the headspace will change depending on how much force it takes to size the case (the press deflects under load). I like setting the die so it contacts the shell holder with some force (near equal to the force required to size) and use Redding competition shell holders to vary the shoulder bump. This works with presses that cam over and those that have a stop. If the die and the shell holder remain in contact at the end of the sizing the results will be consistent.

 

[Tokay444]

Yeah, like I said above, I have extremely consistent results, without all that. Seems others do as well, so I don’t know who’s telling who what, but my experience tells me all I need to know.

 

[CA_Shooter]

What is a good shoulder bump variation? +/- .0005 (for example 1.5425 to 1.5435)? +/- .001 (for example 1.5415 to 1.5435)?

 

[Richard Coody]

Years ago I used to adjust my FL dies down just enough that my brass would chamber in the rifle. I may have to go back to this...
I apologize upfront for beating the dead horse, but frankly, I am baffled at the moment.

I've been working on my 6.5 Creedmoor & 6.5x284 brass for my NRA match rifles. Both have brand new barrels installed by one of the best in the game. My brass is now all once fired from last season. So I dug out my Hornady shoulder bump set once and thought I would try and bump down a quantifiable amount, .001-.002 inches.

I started out by measuring my fired brass, and right off the bat I suspected a problem. I am measuring up to .002 variability in fired cases to the datum line. Hornady digital caliper, Hornady bump gauges, different size gauge for each cartridge of course. Same variability across the board, regardless of cartridge.

I then went thru the process of backing the FL bushing die back from the shell holder one full turn, then working down in 1/8-1/4 turn increments and trying to measure a difference. Even with my FL die all the way down on the shell holder, I can maybe [and I emphasize MAYBE] measure .001 difference from a fired case. In my investigative readings, a die screwed full down should maybe bump the shoulder .004-.007 inches, is that a fair statement?

So I have to ask, what the heck am I doing wrong?

I use Lee shell holders, and Redding Bushing Dies, I realize that's kind of like pairing a Cadillac and a Nissan. Only set of shell holders I've ever owned. I ALWAYS use the same specific shell holder for each specific cartridge. But now I am questioning the specs of the Lee shell holders?

• Maybe they are "tall" and limiting shoulder bump [limiting die adjustment too far down]? Maybe the .001 I see if right...
• Or is the Hornady aluminum shoulder gauge set junk? Maybe I just can't measure what's happening?

Either way, I can, and maybe should go back to the old way of just sizing enough so the brass chambers, but it sure would be nice to quantify that and record it. In these new times of components scarcity, its prudent to reevaluate ones process to optimize usage life.

Thanks for all the assistance. The one good thing COVID has done is give me more time to work on my shooting, rifles, reloading and dig deep back into long range shooting.

Years ago I used to adjust my FL dies down just enough that my brass would chamber in the rifle. I may have to go back to this...

nothing wrong with that technique. Your rifles chamber is the best chamber gauge you can have..

from what I have read on this thread your brass is not fully fireformed. If a piece of fired brass chambers easily its not fireformed. Just set your full length die up to size the neck and not touch the shoulder load and shoot. When you get a piece of fired brass that chambers tight then measure base to shoulder datum with your comparator. Then slowly thread the die in in tiny increments, you will feel resistance when you get to the shoulder, and size and measure again. It is easy to overdo it at this point. Tiny die movements make large changes in the shoulder bump. Might take 2 or 3 pieces of brass before you get that die adjusted for 1 or 2 thousandth bump. Then chamber that piece of brass. If it chambers easily then lock that die down and don't mess with it any more.

As for consistent shoulder bump as your brass work hardens from the firing/sizing cycle your bump will become more difficult to maintain consistency. My experience is annealing cures this problem. Otherwise as your brass ages you are going to be chasing that bump.

 

[ronemus]

What is a good shoulder bump variation? +/- .0005 (for example 1.5425 to 1.5435)? +/- .001 (for example 1.5415 to 1.5435)?

With the process I spelled out in an earlier post, I can get bump variation of +/-0.0005, and that's my goal. I start looking for problems if I see more variation. Note that's for one lot of brass, fired the same number of times in one rifle.

 

[Uncle Ed]

257Roberts

Pausing at the top of the ram stroke for 4 or 5 seconds will make the shoulder location more uniform.

If any sizing lube is forced/squeezed upward to the shoulder of the die the shoulder location will "NOT" be uniform.

The reloading manuals tell you after lubing the cases to wipe the shoulder and neck off.

Whatever happens, do "NOT" go to another reloading forum and ask F. Guffey........
"Why can't I measure shoulder bump". (it might make you go insane)

​

Inconsistent headspace?​

• Thread starterJohn Rambo
• Start dateJan 13, 2018

https://forum.accurateshooter.com/threads/inconsistent-headspace.3942700/page-2

 

[Metal God]

Never understood camming over. Doesn't make sense to me. You can only shove the case so far into the die?

To be honest , I did not read all 5 pages hope this is still relevant .

It's not about pushing the case farther into the case , it's about taking the flex out of the press .

This is a pic of a Hornady press and the die and shell holder touching when the ram if fully up with NO case in the die . Note no gap between the die and shell holder .

This pic is of the same die setting but this time the ram is fully up while sizing a case . Note there is now a gap between the die and shell holder .

When you put a load on/into the press like what happens when sizing a case that load results in press and linkage deflection . This is often what is happening when someone says they can't bump there shoulders enough . They believe when there die and shell holder are touching on initial set up . They are also touching when they size there cases and they often are not . This results in those inconsistent shoulder bumps .

If they screwed the die down another 1/4-ish turn they would get full cam over where the die and shell holder stay in contact with one another through cam over . This will result in a much more consistently sized case ( head to datum ) . The problem with real/full cam over ( firm contact between die and shell holder ) with a "standard" shell holder ( deck height .125 ) is this often sizes the case ( bumps the shoulder back ) further then the .001 or .002 we usually want .

Press deflection is caused by several factors - how work hardened the case/shoulder is , lube used , quality/strength of press . Your cases will resist there sizing causing the press to deflect more or less depending on those factors . I believe one poster said they fixed there inconsistent sizing by annealing there cases . This is one way that can help solve the problem because the softer neck and shoulder resist sizing less resulting in less press deflection and less case spring back .

Although annealing is a method that can help solve the inconsistent sizing problem . It's a costly one ( price of the annealing machine ) that also takes up a good bit of time and energy to do so . I do anneal my cases but not after every firing ( I'm not shooting long range comp ) I don't feel the need . Rather I anneal every 4th firing or so . This causes my cases to not only get work hardened but work hardened quite inconsistently . This results in some cases resisting there sizing more then others .

Ok no problem I just screw the die down to make hard contact with the shell holder and I should be gtg right - WRONG . My issue and most of us is that we often only want to bump the shoulders a couple thousandths . The problem is having hard contact between the die and shell holder sizes the case ( head to datum ) to much . So to get the proper bump you need to back the die out a bit but when you do we reintroduce all that case resistance , press deflection and spring back again .

That's where the Redding competition shell holders come into play . There deck heights get deeper by .002 incrementally through a set of five shell holders . Meaning the Redding standard shell holders deck height is .125 the the first comp shell holder deck height is .127 the next is .129 , next .131 etc etc . This allows you to have hard/full contact between the die and shell holder while being able to size your cases longer ( head to datum ) in .002 increments . This removes all the press deflection problems and results in very consistently sized cases even after several firings .

How cool or useful are the Redding competition shell holders . With out getting into exact numbers . I reload for many multiples of rifles in the same caliber/cartridge . Many of which need the cases sized different ( head to datum ) then the others . In the 7 or so years I've been using the comp shell holders I've never needed to adjust my die to accommodate for a different rifle . I simply use the comp shell holder that gets me the bump I need . Which is much quicker with less fuss then annealing every time .

Hope that helps
MG

 

[cw308]

Metal
Great Post, makes perfect sense. I use the same system . Hope Things are going well.
Chris

 

[Coyotefurharvester]

MG, I learned something today, thank you. One question can the competition sh be used with other brands of dies(rcbs,Hornady) ? Oh, 2 things learned today, thanks out to Tokay also, I can see a slight change in my procedure could eliminate the occasional need to trim.

 

[RegionRat]

@Coyotefurharvester , The Redding Competition Shell Holder set can be used with any brand of die that uses a standard shell holder.

The same can be said of any standard shell holder. They ”should be” a standard 0.125” deck height. However, with that said, I have done this long enough to have encountered some that were off by enough to annoy me. I mark those up to make sure they don’t creep into a session by accident. I keep them cause they still come in handy when used similarly to the Redding Comp set. Sometimes these defects drop right in between the 2 mil step size so I keep them.

And not to add more confusion, but I have several sets of the Redding Competition Shell Holders and more than one has had a particular piece that I had to ask for replacement because it wasn’t what it was supposed to be. They sent replacement without hesitation.

The first time I caught this, I was creeping down by sizing a new set up. I start with the biggest one and they should come down in 0.002” steps. When I got close, one of the step changes didn’t act right. After a little head scratching, I measured the shell holders and found that one step was way off. Like I said they replaced it with a proper one, but I always check a new set to make sure they step the way they are marked. It is easy to do with the tail stock on a caliper or using a depth micrometer.

 

[cw308]

Just check the depths of the decks first #10 being the deepest .135

 

[rogn]

Years ago I used to adjust my FL dies down just enough that my brass would chamber in the rifle. I may have to go back to this...
I apologize upfront for beating the dead horse, but frankly, I am baffled at the moment.

I've been working on my 6.5 Creedmoor & 6.5x284 brass for my NRA match rifles. Both have brand new barrels installed by one of the best in the game. My brass is now all once fired from last season. So I dug out my Hornady shoulder bump set once and thought I would try and bump down a quantifiable amount, .001-.002 inches.

I started out by measuring my fired brass, and right off the bat I suspected a problem. I am measuring up to .002 variability in fired cases to the datum line. Hornady digital caliper, Hornady bump gauges, different size gauge for each cartridge of course. Same variability across the board, regardless of cartridge.

I then went thru the process of backing the FL bushing die back from the shell holder one full turn, then working down in 1/8-1/4 turn increments and trying to measure a difference. Even with my FL die all the way down on the shell holder, I can maybe [and I emphasize MAYBE] measure .001 difference from a fired case. In my investigative readings, a die screwed full down should maybe bump the shoulder .004-.007 inches, is that a fair statement?

So I have to ask, what the heck am I doing wrong?

I use Lee shell holders, and Redding Bushing Dies, I realize that's kind of like pairing a Cadillac and a Nissan. Only set of shell holders I've ever owned. I ALWAYS use the same specific shell holder for each specific cartridge. But now I am questioning the specs of the Lee shell holders?

• Maybe they are "tall" and limiting shoulder bump [limiting die adjustment too far down]? Maybe the .001 I see if right...
• Or is the Hornady aluminum shoulder gauge set junk? Maybe I just can't measure what's happening?

Either way, I can, and maybe should go back to the old way of just sizing enough so the brass chambers, but it sure would be nice to quantify that and record it. In these new times of components scarcity, its prudent to reevaluate ones process to optimize usage life.

Thanks for all the assistance. The one good thing COVID has done is give me more time to work on my shooting, rifles, reloading and dig deep back into long range shooting.

Anneal. Your worries will go away.

 

[Metal God]

You measure camover in multiples of "0" , haha You are at zero when "camming" over regardless of your components . Maybe looking up the definition of camming would be helpful to understand when and if a press does so . To be honest I think the term cam over is over used . IMHO what should be said is you should have hard/firm contact between the die and shell holder when sizing your case for the most consistent results . It doesn't matter if the press cams or not .

SAAMI specs have tolerances so there are no perfect worlds here .

Chambers are almost never perfect to match your die , don't even understand the point of asking the question . Because they never match and ALL presses flex/deflect is the very reason the comp shell holders and hard/firm contact between the die and shell holder are so important to consistent sizing

How do you know if a/your press cams over ? It says so in the instructions . If you don't have the instructions . Use the definition you looked up on camming action . Screw your die down to have light to moderate contact with the shell holder when the ram is full up and see if your press needs to cam out of that position to bring the ram down . If it drops straight down with little to no force needed your press likely does not cam over . If it takes some force to get the ram moving back down and almost feels like it snaps over then is super easy . That is the camming force you feel .

 

[Tokay444]

My consistent results disagree with needing to touch die to shell holder.

 

[M-61]

What is a good shoulder bump variation? +/- .0005 (for example 1.5425 to 1.5435)? +/- .001 (for example 1.5415 to 1.5435)?

5 ten thousandths is some serious measurement.

 

[Metal God]

My consistent results disagree with needing to touch die to shell holder.

Do you anneal every firing ? There were a few caveats in my posts it’s important people keep those in mind and understand this is not a blanket statement .