Why can't I measure shoulder bump?

[bsekf]

I have always blamed it on non-uniform spring back. If you twirl the case in the comparator, the measurement will often change.

 

[cw308]

I never like to add any type of stress anymore , I'm the guy who snapped the lug bolts on my car from over tightening, learned my lesson a long time ago. I do remove the slop from my dies when setting up , even use a O ring under the lock ring , my sizing is consistent without stressing the press , maybe I'm just lucky . I wet tumble , brass is spotless and I use RCBS Case Lube and lube by hand , it sizes very easily . It could be sizing with brass that isn't properly clean and lubed makes the sizing more difficult? I know I'm gonna get jumped on for this one , Be Nice Guys.
Chris

 

[Orr89rocz]

I have an old set of bench rest dies (i think bonanza?) for a .257 rob that will not shorten a case more than a given amount no matter how much cam over there is and no matter how far down the die is screwed down. Not sure what that is all about but i leave it as is, there may be only .001” of bump back, still chambers fine with a slightly stiff bolt on close.

 

[Burnt Powder]

All of mine are .125

I’ve got probably half dizen or more brands of shell holders, other than one Pacific shell holder they are all within a .001or two. Keeping the ram and shell holder clean is very important too. I’ve faced several .001s off shell holders to get what I want and sometimes I like the thicker Pacific shell holder for various reasons. I have a lathe and make my own measuring standards, no special tool. Not concerned about what the measurements are, just how they compare and fit. My B&S dial calipers is a pretty danged accurate measurement tool! Good enough for handloading!

 

[Tokay444]

My dies don’t touch my shell holder. I get EXTREMELY repeatable bump, and runout numbers less than .001”, to the point I stopped checking. I don’t measure bump with a comparator on a caliper either (good for +/-.002”). I use a fixture with a dial indicator.

 

[M-61]

Anyway, never mind, I have no interest in what you to have to say.

If indeed this were true why do you reply?
Anyway your 'tone' and wording is uncalled for especially to Boyd Allen who has contributed much to this site.

 

[DJSBRS]

We arrived at the amount of time in the flames of the annealer that gave that result, while preserving enough hardness in the neck so that heavy bullets loaded in magnums, fed from magazines did not move. The press was a Forster B2, Later we found that the problem returned after a couple of firings, which indicated that, going forward, we would have to anneal every other firing to keep the bump uniform. The first time we tried cases, the anneal was not enough. We added a second to the dwell time in the flames and got what we were looking for.

You are exactly correct Boyd. And on some very rare occasions, a particular piece of brass will continue to give you problems due to that piece of metal make up. Do your self a favor and trash that piece off brass so you will have a piece of mind later on.

DJ

DJ's Brass Service

 

[BoydAllen]

You are exactly correct Boyd. And on some very rare occasions, a particular piece of brass will continue to give you problems due to that piece of metal make up. Do your self a favor and trash that piece off brass so you will have a piece of mind later on.

DJ

DJ's Brass Service

Thanks for the tip.

 

[MagnumManiac]

If indeed this were true why do you reply?
Anyway your 'tone' and wording is uncalled for especially to Boyd Allen who has contributed much to this site.

Because I felt like replying...just like I am replying to you.
This is your OPINION.

 

[K22]

Wow! Probably missing something here but I've never seen something so relatively simple be made so complex. A historical perspective from an "old fart."

No reason to get emotional or nasty - Remember, there is only two reason to size a case 1). So it chambers in the rifle preferable without significant resistance, and 2). So there's enough neck tension to hold the bullet.

Before all this gadgetry of bump gauges, case gauges, micrometer gauges etc. experienced reloader's learned that following the die mfg. instructions resulted in over sizing the case so they began a trial and error process of adjusting the FL die to produce just enough sizing so the case would chamber optimally to enhance precision.

They also learned that as cases aged from repeated firing some adjustment may be necessary to maintain this optimum sizing. The rifle's chamber became the ultimate gauge to assess optimum sizing. It was really quite that simple - it still is!

Enter the gauges which enabled reloaders to measure and record the exact amount of sizing. That was convenient and effective as far as it goes but it doesn't change the original premise as to why cases are sized.

Add in that each rifle, lot of cases, brand of cases, dies, and slop in presses can be different then it become obvious that there are no absolutes - you have to adjust to those variables to produce the optimum amount of sizing.

So the need for cam over vs no cam over may or may not apply. With my equipment, I can't get any shoulder setback without some degree of cam over depending of the variables involved. But my press and dies are over 50 years old. Also I use a variety of common brands of cases.

Now enter competition shell holders, shims, the Salazar "O" ring method to allow for precise and repeatable die adjustments without having to reset your die lock ring. They all work just fine if you know what your doing and why. It makes die adjustment easier but doesn't change the original premise.

I've loaded thousands of bottle neck rifle cartridges for close to 50 years using necks sizing, partial sizing and full sizing. I've never had a head separation even using the die mfg. instructions which, in most cases, I believe creates too much sizing for optimum precision.

The only times I've encountered sizing problems is with neck sizing and partial sizing since over time I'd encounter hard chambering in some rifles. Also, using cases fired in other rifle chambers would occasionally create sizing / chambering problems.

Bottom Line: resizing cases in not some mystery process especially with all the modern gadgets that make it easier to make adjustments but you're still trying to accomplish the same results that reloaders have sought since reloading began. Just stay focused on the purpose and don't get caught up in all the measurement mania.

 

[CA_Shooter]

I recently bought the redding competition shell holders. I needed to change my bump, and it took me about 15 minutes (including waiting for my Hornady lube to sit for 60 seconds per shell) to set up the right bump amount

I suggest the redding competition shell holders

 

[Tokay444]

I recently bought the redding competition shell holders. I needed to change my bump, and it took me about 15 minutes (including waiting for my Hornady lube to sit for 60 seconds per shell) to set up the right bump amount

I suggest the redding competition shell holders

If it took me 15min to adjust my die to the amount of bump I needed, it would be because I was doing something else for 13.
Just saying. Measure bumped case. Measure bottom of die to bottom of lock ring. Subtract and find the difference. Thread die in or out by the difference, and be done.

 

[Murray Brook]

@BoydAllen
In one of your prervious posts you mentioned you had a fancier way of setting up shoulder bump. I would be most interested in reading what you have to say on this. TKS

 

[BoydAllen]

@BoydAllen
In one of your prervious posts you mentioned you had a fancier way of setting up shoulder bump. I would be most interested in reading what you have to say on this. TKS

Since you asked.....With once fired brass, we really don't know how far short of tight at the shoulder in the chamber we really are. Most of the time simply sizing to equal the once fired dimension works fine, but if we want a better idea of just where we are you can try this. First of all take the primer out of one of your once fired cases. then put a piece of Scotch tape on its head and trim it so that it is like a washer on the flat surface only. Trim to the top of the bevel at the bottom of the rim, and cut out the part over the flash hole. Next take out your bolt's firing pin assembly, then try the fired round in your chamber, but do not force it at all. The bolt will probably not close. Then you use whatever tool you prefer to measure the head to shoulder of this case. Starting with the die backed out a little from touching the shell holder, perhaps a sixteenth of a turn or so, with the top of the die and bushing removed (To remove a bushing from a die that is in a press simply shove a neck brush into the bushing and pull it out.) lube the case and start sizing, making the slightest of adjustments, and then measuring until you see that the taped case is .001 shorter (head to shoulder) wipe off all the lube and try it in your rifle. If the bolt will still not close, adjust the die by so small an amount that you are really not sure that you moved it, relube, resize and measure the case so that it is .001 shorter, and then wipe off the lube and try it in the rifle. At this point you should be able to close the bolt with some feel, or the handle may drop. If it drops, you are there, unless it is for a hunting rifle in which case you may want to bump another thousandth. I shoot my match, and usually my varmint brass in rotation so that all of the cases in a set get fired and sized the same number of times, but even so, when only bumping .001 with brass that has not been annealed, for critical work you will want to check to see if they all have been bumped to the same dimension, the reason being that you can shoot small with all snug, or all relatively loose, but mixed will, in my experience open up your groups. Remember that one full turn of a die gives .071 of up or down movement in the press, so trying to do an adjustment of .001 can be tricky. If you blow it, and go past your mark, you can start again with another once fired case. I usually load at the range which allows me to fire the same case with a safe but warm load several times until the shoulder to head dimension stabilizes at a maximum and then set my die to bump back .001 from that, but there are times when I do not want to make a special trip just to set up a die and size a few cases. It is for those occasions that I came up with this method. Questions?

Added a little later: Obviously having a PMA Tool Micro die adjuster makes doing the adjustments very simple, and you could also use die shims, or Whidden's dies or lock ring that are set up for exact adjustments. In any case, this should give you the basic idea.

 

[Murray Brook]

Thanks Boyd. No questions I understand your procedure. I generally use the Hornady Comparator the standard way, but this way seems fool proof.

 

[Coyotefurharvester]

Or partially seat a spent primer in a fired case( measure oal) and chamber closing the bolt completely. Measure case again, subtract difference. Add what you want for hs. Divide your die( one full turn) adjustment height by the remainder from your case measurements. Examples: .005(final case measurements) .071(amount of vertical die movement in one full turn) . Mark your press in 12 equal segments(each will equal 0.00591inches in vertical die movement). Turn die in to correct mark. Size brass test fit or measure.

 

[Dave Marshall]

Apparently I have no social life, or meaningful things to do. Most folks spend their weekends at BBQs or home maintenance or ball games, I spend my day pondering brass and taking measurements and trying to figure out what it all means. Fascinates the hell out of me. Anyways, I took 30 pieces of 3X fired Lapua 308 brass and did a little data collection. I spent some serious time with my Hornady bump gauge tool and figuring out how to use it consistently and then playing with my Redding FL bushing die to size in various increments.

Of the 30 pics, fired late last fall in my Palma gun, all of which gave .30-.40" groups off the bench, the fired length from head to shoulder datum ranged from 1.625-1.628", with the mean value being 1.626". The listed SAAMI chamber spec is 1.630-1.640", my 3X fired brass is still shorter than SAAMI.

I then used 2 different presses, a basic Lee challenger single stage and Redding T-7 turret, using the same Lee universal shell holder [mine measured .124] and screwed the Redding FL bushing die until it firmly contacted a raised ram. Both presses gave the exact same result. All 30 sized pieces of brass GREW in shoulder length by exactly .002".

Using the same two presses and shell holder, it took an additional "1/16th to 1/8th" [very very slight] die turn [past initial contact] to bump the shoulders back down the .002", to the original fired shoulder lengths. [Just as a side note, in all cases, the OAL length of the brass grew by .004-.005"].

Another interesting point, annealing made no difference in the numbers. I annealed half the batch just to compare, and the exact same .002" growth, and then .002" set back were observed. The OAL growth was also the same at .004".

I then realized thru numbers, at least for this batch, that I didn't need to be bumping shoulders at all, because even when the shoulders grew by .002", the worst case was 1.630" and that brass still easily chambered in my gun. So then I wanted to know what the chamber of my gun actually was, so I went on the hunt in my stash of brass for something long and obnoxious, and found some old once fired LC72 match in the 1.645" range. Backing the die out and running down in micro increments, I found that a 1.631" shoulder will not chamber in my gun, no way no how, but a 1.630" will chamber just fine.

What's interesting to note, the die position for achieving 1.630" with the LC72 Match was past initial shell holder contact, or slightly more "cam over" than with my Lapua brass. This makes sense to me as the brass was bigger to start with and likely took more camming force to cause the same amount of brass engagement into the die body.

All this raises more questions though, and I am anxious to discover more details.

• Is all brass created shorter than SAAMI initially?
• Is there a better way to measure chamber dimensions outside of chamber casting or incremental sizing of brass?
• At what rate does brass spring back or shrink happen?
• There are many different reamers/brands for the same cartridges, how different are the dimensions?

I am anxious to try some of this process again with freshly fired brass or a different cartridge & gun to see if the incremental measurements are similar.

My initial conclusion is this, the overall process is extremely repeatable, and even my cheap tools can give very consistent results. I made some very poor "universal" numerical assumptions that I proved wrong thru a little data collection. [Just because brass is fired in your gun, don't assume that's your chamber dimension]. I think the takeaway here is that obviously every gun, brass, press, die, shell holder is NOT the same, and everybody's process by default must be a little different to achieve the same [or proper] result. Each individuals process is likely different for each cartridge they load for as well. If a person takes the time to do some measuring of what is actually happening with their tools and what works in the specific firearm, I think the whole process can be very precise and repeatable. I demounted and remounted all my tools into multiple presses, even removed and remounted my Hornady bump gauge, and I was able to repeat every measurement I took. This activity sure helped ease some of my questions & concerns, but also taught me that I need to pay a little closer attention to initial measurements, die setting and record keeping.

I hope this post was helpful. Not meant to stir the pot, just sharing my findings.

Are you using an expander ball on your decapping stem when you resize your brass?

At one time, I decided I wanted to try using expanders to fine tune neck tension. The brass I was sizing (6xc) had been fired a few times and had developed donuts in the neck/shoulder junction. As the case was withdrawn from the neck bushing on the press downstroke, the expander ball produced enough drag to stretch the shoulders slightly and take a few degrees out of the shoulder angle. I figured this out after I had sized about 1500 cases, lol. I felt like quite the dummy. I gave up on the expander idea as I absolutely refuse to neck turn that much brass. I removed the expander and bumped the shoulders again. Most of the cases feed and fire just fine.

One thing I will mention is that Lapua brass seems to be a bit harder to anneal than other makers. It takes a little more time in the flame to get a consistent result. I would bet after three firings your .308 brass is pretty hard and would expect more spring back after sizing. I also wouldn’t bother using the Lee press for the kind of precision you’re trying to achieve.

 

[fatelvis]

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.

 

[searcher]

My dies don’t touch my shell holder. I get EXTREMELY repeatable bump, and runout numbers less than .001”, to the point I stopped checking. I don’t measure bump with a comparator on a caliper either (good for +/-.002”). I use a fixture with a dial indicator.

Maybe the dial indicator on your setup is stuck in one position? (Just kidding). I have multiple presses, including some really nice gear like the Bruno D press. I will do runs of hundreds to thousands of pieces at a time in various calibers. I do not use dies that require camming over to set shoulders where needed. I have never once gone through a run of brass and ended up with variation of under .001" on the run. I'm pretty amazed your brass has no memory and your press no runout. I'm envious.

 

[Tokay444]

Maybe the dial indicator on your setup is stuck in one position? (Just kidding). I have multiple presses, including some really nice gear like the Bruno D press. I will do runs of hundreds to thousands of pieces at a time in various calibers. I do not use dies that require camming over to set shoulders where needed. I have never once gone through a run of brass and ended up with variation of under .001" on the run. I'm pretty amazed your brass has no memory and your press no runout. I'm envious.

I generally process my brass 100 pcs at a time. Sometimes less, but not more, and I follow the exact same method every time.
Deprime.
Anneal.
Wet tumble. (With or without pins. Lately without)
Chamfer.
Lube.
Body size/shoulder bump.
Neck size.
Dry tumble to clean lube.
Mandrel.
Prime.
Charge.
Seat.
This has been my regiment over 15 firings so far of Lapua 6.5 Creedmoor SRP brass, and 20 firings of Alpha 6.5 Creedmoor SRP brass before that, and 10 firings of Alpha 6.5 Creedmoor LRP brass before that. I made and learned from my mistakes in charge weights and speed chasing in the LRP Alpha brass.
You’ll notice I don’t trim either. I don’t need to. My brass never grows. It did when I thought I could save some time switching to a Mighty Armory Gold Match die, but having to trim ended up cancelling out the time savings of eliminating three press operations, and that die caused me to have shoulder sooting issues I could never get to the bottom of, so I’ve switched back to the above method.
I’m waiting on a 6BR barrel and I have about 350 pcs of brass lined up for it, so my batch sizes are slated to increase. I hope to observe the same consistency.