Shoulder bump question

[CamTheBam]

Hi Guys,

I read a lot of comments about bumping the shoulder back by .001 or .002". Should I be adjusting my FL die to bump the shoulder back on fired cases, or on cases that have already been returned to SAAMI spec?

With my comparitor, virgin .308WIN Lapua cases and factory ammo seem to measure at 1.616", and my fired cases measure 1.623" - so am I aiming for 1.621-1.622"?

Many thanks,

Cam.

 

[Rsadams]

I do the ones fired in my rifle not new brass...
Check the brass fired out of your rifle then bump it back .002 for a bolt action..more for an automatic.. normally.003 , I do .004. for mine..

 

[CamTheBam]

That's great, many thanks guys - I'm never sure what to believe on the internet, but now I know!

 

[jimbires]

on new virgin brass , I neck size only for 2 or 3 times to get new brass fully expanded . when I get a piece of brass that is getting tight to chamber this is the brass I use to set up my dies . otherwise you are setting up your dies on partially expanded brass .

 

[fguffey]

With my comparitor, virgin .308WIN Lapua cases and factory ammo seem to measure at 1.616", and my fired cases measure 1.623" - so am I aiming for 1.621-1.622"?

There is a step sequence of events that start when the trigger is pulled, it has to be a boring story because no one knows the steps or if they do they do not understand them. POINT: If you are using a datum on the shoulder to measure the distance from the datum to the case head and the difference between a new/never fired case and a fired case is .007" you are already out to a no go-gage length chamber. Meaning: the first time you fired the case there is a chance the case stretched .007" between the case head and case body.

There is a problem I can do nothing about, manufacturers do not sell new cases for reloaders that know and understand what they are doing. If they did they would sell cases that would not chamber because the length of the case from the shoulder of the case to the case head would be too long to allow the bolt to close. I use the length of the case top off set the length of the chamber; so I ask: How does that work when the case is too when I start?

Back to the information you have furnished. Your fired cases are .007" longer than unfired/new cases from the shoulder/datum to the case head. I would suggest you determine the ability of your press, die and shell holder to return a case to minimum length/full length size. There is a small chance the case will measure the same as your new/unfired cases. After you have determined what a full length sized case looks like I suggest you start backing the die out. Because I have more confidence in my dies, shell holder and press I use a feeler gage to make adjustments when backing the die out. If I had cases that were being fired and stretching .007" I would adjust the die off the shell holder .004" and then measure the length of the case from the shoulder to the case head to check results.

Bump? I know, it sounds cool and you get immediate neighborhood acceptance when you use the term; it is like keeping your lawn mowed but for me bump sounds like an accident. Please understand, I have bump presses, all of my bump presses are cam over presses (according to the instructions).

F. Guffey

 

[M-61]

Quote from fguffey"
"Bump? I know, it sounds cool and you get immediate neighborhood acceptance when you use the term...."

Well said.

 

[ireload2]

If you don't like bump what do you call pushing the shoulder back?
Is that like moving your lawn so you don't have to move the lawn mower?

There is a step sequence of events that start when the trigger is pulled, it has to be a boring story because no one knows the steps or if they do they do not understand them. POINT: If you are using a datum on the shoulder to measure the distance from the datum to the case head and the difference between a new/never fired case and a fired case is .007" you are already out to a no go-gage length chamber. Meaning: the first time you fired the case there is a chance the case stretched .007" between the case head and case body.

There is a problem I can do nothing about, manufacturers do not sell new cases for reloaders that know and understand what they are doing. If they did they would sell cases that would not chamber because the length of the case from the shoulder of the case to the case head would be too long to allow the bolt to close. I use the length of the case top off set the length of the chamber; so I ask: How does that work when the case is too when I start?

Back to the information you have furnished. Your fired cases are .007" longer than unfired/new cases from the shoulder/datum to the case head. I would suggest you determine the ability of your press, die and shell holder to return a case to minimum length/full length size. There is a small chance the case will measure the same as your new/unfired cases. After you have determined what a full length sized case looks like I suggest you start backing the die out. Because I have more confidence in my dies, shell holder and press I use a feeler gage to make adjustments when backing the die out. If I had cases that were being fired and stretching .007" I would adjust the die off the shell holder .004" and then measure the length of the case from the shoulder to the case head to check results.

Bump? I know, it sounds cool and you get immediate neighborhood acceptance when you use the term; it is like keeping your lawn moved but for me bump sounds like an accident. Please understand, I have bump presses, all of my bump presses are cam over presses (according to the instructions).

 

[BoydAllen]

There are a couple of issues that the (very well done) video did not cover. First of all, one needs to verify that a die reduces the body diameters of fired cases. This should be done at the outset, and only needs to be done once for a particular die chamber combination. If you do not look at this you can end up chasing your tail trying to get the combination of bolt close and measured shoulder bump that you want. The other issue has to do with tool selection. Because of the issue that Alex mentioned relating to the angled contact flat that Sinclair's comparitor insterts have, I prefer the Hornady comparitor, because its inserts are designed to make line contact on case shoulders. This does not eliminate the potential problem of mismatched die and chamber shoulder angles, but it does eliminate one variable. Another thing that I would encourage shooters to do is to do their own testing, including what works better for their particular situation for bolt close. I say this because there are some variables that can vary from situation to situation that can affect a rifle's preference. Having said that, I do believe, that it is desirable that all shots in a group have the same feel as the bolt is closed. IMO mixed feel is detrimental to accuracy.

 

[dkhunt14]

Like Boyd mentioned, we need clearances in other places as well. Amazing the problem solving skills we have with just a few tools, and paper and pencil!

Tom

Boy your getting pretty good at this video and meme posting. I can't even post a pic. Did Donovan teach YOU? Matt

 

[dedogs]

After you have determined what a full length sized case looks like I suggest you start backing the die out.

Is the reason for doing this to determine what the die is capable of? In other words, to find if the die closely matches the chamber dimensions?

 

[fguffey]

And I wonder, reloaders claim they can move the shoulder, back to wondering; I have never had a reloaders prove he can move the shoulder, nor have I ever found one that can prove the shoulder does not move. I have had a bunch of them get wildly indignant, seems it is easier to get indigent than for them to say "I do not know". And then there is the precision; "I bump my shoulder back .002", I have been waiting for the Googler searchers, I do remember when I was told it was impossible, seems there were too many variables and tolerances and all of that pesky snap back, jump back or spring back brass. And now every reloaders is doing it.

F. Guffey

 

[SheepDog]

F. Guffey,
When you say "move the shoulder back" are you talking about the case?
If you are then the formation of a 30 Herret from a 30-30 requires moving the shoulder back.
If you are not talking about the case then what is it that you consider the shoulder?

 

[hunter243sgk]

I cant help but to think some of you make reloading WAY to complicated! It is not rocket science.

 

[SheepDog]

Yes, well it really is rocket science - it's just that most of the science has been removed with data that is proven to be safe in modern tubes in use.

You are placing a propellant into a tube that is closed at one end and restricted at the other. It is just that the restriction is what you are propelling.

 

[Sheldon N]

And I wonder, reloaders claim they can move the shoulder, back to wondering; I have never had a reloaders prove he can move the shoulder, nor have I ever found one that can prove the shoulder does not move.

 

[M-61]

fguffey
"...I have never had a reloaders prove he can move the shoulder, nor have I ever found one that can prove the shoulder does not move...."

OK....if the shoulder can't be proved to move, nor proved NOT to move where does this leave us?

 

[ireload2]

The head of the case is the primary datum bubba. If the dimension from the case head surface changes by definition the shoulder has been moved.

And I wonder, reloaders claim they can move the shoulder, back to wondering; I have never had a reloaders prove he can move the shoulder, nor have I ever found one that can prove the shoulder does not move. I have had a bunch of them get wildly indignant, seems it is easier to get indigent than for them to say "I do not know". And then there is the precision; "I bump my shoulder back .002", I have been waiting for the Googler searchers, I do remember when I was told it was impossible, seems there were too many variables and tolerances and all of that pesky snap back, jump back or spring back brass. And now every reloaders is doing it.

F. Guffey

 

[Toby Bradshaw]

fguffey
"...I have never had a reloaders prove he can move the shoulder, nor have I ever found one that can prove the shoulder does not move...."

OK....if the shoulder can't be proved to move, nor proved NOT to move where does this leave us?

It leaves most of us with fguffey on our ignore list.

 

[mike06]

I have 3 rifles in 308 and have been reloading for the past 20 plus years here is a first for me. My new Ruger Precision less than a 100 rounds fired. I loaded up some rounds just for break in and I always check my brass with my rcbs case mic. The new Lapua all came in at .000 headspace on the gauge. I go to in range fire 15 rounds and come home. Upon checking the headspace the gauge now reads -.002. I have never seen a decrease in the case ever. I am thinking the case body did expand some but the length stayed the same. All cases re-chamber fine without doing any resizing. That is how I determine if I need to bump the shoulder or just neck size.

 

[msinc]

I have read this entire string and there are some intelligent and lucid comments....but, if I set up a dial caliper with a comparator to check headspace and zero it it with a headspace gauge and my fired brass is .007" longer {over zero} the absolute first thing I am going to do is check headspace on the rifle!!!!!!!!!!!!!!!The second thing I am going to do is fix the GD thing, because unless it's an M-1 Garand that typically stretches brass .008"....there is a problem. Once I have a rifle that gauges with dead on zero headspace then I will start worrying about reloading for it. And don't even try to tell anyone that .004" headspace is "okay", because we all want zero. If I barrel a rifle for you and tell you, "yeah, missed the headspace a little...so I just left it at .004".....yeah okay right, and you are not going to have me set back, rechamber and do it right????