FL shoulder bump question

[OG-danimal]

Hey all,
I've been sizing my 2x fired hornady 6.5 prc brass and noticing some variance in my bumps. I meticulously set the shoulder bump to 1.644 and seem to get about 3-4 cases perfect then they start opening up from -.0005 to +.0015. Is this normal and/or a big deal or just roll with it? I'm using whidden bushing dies, RCBS rock chucker, and annealed after each firing prior to sizing.
Thanks

 

[DoneNOut]

Hey all,
I've been sizing my 2x fired hornady 6.5 prc brass and noticing some variance in my bumps. I meticulously set the shoulder bump to 1.644 and seem to get about 3-4 cases perfect then they start opening up from -.0005 to +.0015. Is this normal and/or a big deal or just roll with it? I'm using whidden bushing dies, RCBS rock chucker, and annealed after each firing prior to sizing.
Thanks

Happens to the best of us. I get a 2 thou variance and all is well. Heck, I get bug holes blowing cases to AI during fireform. LOL

Edited: Holy smokes. -.0005-.0015 + is outstanding. You coyishly bragging?

 

[entoptics]

That variance wouldn't bother me, but it might for some.

In my experience, getting your lubrication applied consistently will help reduce variation.

 

[OG-danimal]

Rodger that, thanks guys!

 

[RegionRat]

Using typical tooling and a caliper, you could expect to see a 2 mil uncertainty just measuring any one sample over and over.

In industry, we have to assume that much just based on the caliper, the tooling, the nature of the sample being non-rigid and less than perfectly smooth, etc..

If we gave a group of operators the same tools and a caliper, and ask the group to measure the same Go-Gage and go around several times each, we would get a 2 mil variance on a good day, and worse on a bad day. And a Go-Gage is far smoother and more rigid than an actual sample of cartridge brass.

Your numbers are normal and if you keep them there you are doing above average. If you ever have some change laying around... buy yourself the Go-Gage and practice with that before any session and drop back to it whenever you start wondering about your work.

 

[DoneNOut]

Using typical tooling and a caliper, you could expect to see a 2 mil uncertainty just measuring any one sample over and over.

In industry, we have to assume that much just based on the caliper, the tooling, the nature of the sample being non-rigid and less than perfectly smooth, etc..

If we gave a group of operators the same tools and a caliper, and ask the group to measure the same Go-Gage and go around several times each, we would get a 2 mil variance on a good day, and worse on a bad day. And a Go-Gage is far smoother and more rigid than an actual sample of cartridge brass.

Your numbers are normal and if you keep them there you are doing above average. If you ever have some change laying around... buy yourself the Go-Gage and practice with that before any session and drop back to it whenever you start wondering about your work.

He is sizing brass, not setting headspace. Or am I having a bald moment?

 

[trout004]

Here are some things that I have done to when I was struggling with the same problems with shoulder runout:

1. Like mentioned above, make sure lubrication is applied in a consistent manner.
2. I have found that inconsistencies or slop in the shell holder can cause this. I have made it a practice to make sure the shell holder is in the same position every time. I run a couple of wraps of electricians tape around them to keep them, securing it to the press ram, clocked in a single position for the entire time that I reload that particular lot (this may or may not work for you depending on the type of press that you have.) Rotating the brass and running it up into the die multiple times may also essentially do the same thing, but that takes more work and time...

Good luck!

 

[RegionRat]

Or am I having a bald moment?

My writing sucks and isn't always clear, but you can reference a comparator using a gage.

If you train an operator, you use both the Go-Gage and actual brass samples to teach them several things.

One is how a caliper can vary.
Two is how the anvils affect the outcome.
Three is how the rigidity of the sample can affect the numbers.
Four is how to take a comparator and make it absolute using a transfer standard, as in when the Go-Gage is an actual calibrated value.

 

[Huntsman66]

Those sound like normal variations, i see the exact same shifts. half thou to 1.5 thou is nothing when you add up variations in the case lube and then the fact that the caliper can very a little, dont be concerned its normal.
dont forget the comparator itself is finicky.. spin the case just a little and you can get a 1k difference

 

[trout004]

Those sound like normal variations, i see the exact same shifts. half thou to 1.5 thou is nothing when you add up variations in the case lube and then the fact that the caliper can very a little, dont be concerned its normal.
dont forget the comparator itself is finicky.. spin the case just a little and you can get a 1k difference

I agree that 1.5 thousandths is normal and actually quite good. I misread the original post and was thinking 10 thou.... I am happy if I can keep the lot within about 2 thousandths or less.

 

[ARlife4me]

What about the material the bump is made of and the comparator of being a softer 1? I've been looking into the same tool he's using and have been 2nd guessing whether to use it or not. Yes, this is for the 6.5prc also. 2ndly, what could be the better lube choice for neck bumping if any?

 

[ARlife4me]

Maybe the newer cases are more problematic than older brass? I've been FL sizing every piece since '84. 264wm win super-x over 20 times with no signs of issues.

 

[Mikecr]

I'm someone who sets bump tight, 1thou +/- 1/2.
Given this, it is a real pain, I hate it.

I sneak into it with RCBS case lube, and I keep a working shell holder (whichever happens to work best for this) in a box with gizzys & dies for each chamber. Lately I'm going with ever higher shoulder angle cartridges to make all this easier.

So you may question why precision HS would matter. As far as functional CBTO, my seating windows are big enough to dismiss HS as a factor.
It's still important to me though, as primer crush & consistent optimal striking matters to me.

 

[Dirtrax]

OP- any time you see a change downstream it's the result of an upstream variation. It could easily be as simple as Lube buildup in the die. I too have a .0005" expectation on shoulder bump and typically find it fairly easy to attain. Swabbing the sizing die regularly with a q-tip has been my go to.