How much shoulder bump?

[DngBat7]

Hey all, I am wondering how much to shoulder bump. I have once fired brass out of my rifle. First off, is once fired brass the actual size of my chamber? And I always need to bump back to that point? Or do I not bump the shoulder back on the once fired because it is the actual size of my chamber and that’s what I want? So does that mean I start bumping back the brass .001 on the second time I fire the brass and every time after? Hope I make sense

 

[Dusty Stevens]

dont worry about how far you bump it back worry about how it fits after the first firing. strip your bolt and bump it back til you feel it when the bolt is 3/4 closed. if it falls before bumping it then they need another firing. after that firing check them with a stripped bolt again.

 

[Richard Coody]

Hey all, I am wondering how much to shoulder bump. I have once fired brass out of my rifle. First off, is once fired brass the actual size of my chamber? And I always need to bump back to that point? Or do I not bump the shoulder back on the once fired because it is the actual size of my chamber and that’s what I want? So does that mean I start bumping back the brass .001 on the second time I fire the brass and every time after? Hope I make sense

what rifle, what cartridge

if.your fired.brass will chamber you are not ready for a shoulder bump yet. if it doesn't then find the longest of your fired brass and adjust your die to bump the shoulder .002

 

[BoydAllen]

Typically, brass doesn't get tight, shoulder to head, on one firing. I tell people that if you can, produce a reference case by firing it, neck sized only, actually any way that you can get it to hold a bullet without touching the body, until it becomes tight. Then you can use that case as a reference for setting your die to bump. The amount you will have to bump will depend on how consistent the factory annealing of your brass is, unless you want to measure every case after sizing and go back and resize those that are harder with a different die setting. There is another issue that is typically not a problem with factory dies and chambers but which can come up when dealing with custom chambers. A die can be too big to do a proper job for a particular chamber, which is why I say NOT to rely solely on bolt feel to set a die. If case that has had its shoulder bumped back a max of .002 does not chamber easily (We are talking bolt actions here.) Then you need another die to size brass from that chamber. I have seen it happen that a fellow would use bolt feel with a mismatched die and bump his shoulders back too far to get the feel that he wanted. You cannot adjust your way out of this situation. You need a different die. For once fired brass, I recommend setting your fl die to reproduce the shoulder to head dimension of your fired cases, and check the first sized case for how it chambers. It will probably work just fine. Typically, for brass that I use in my PPC, that seems to be relatively uniform in how it sizes, I bump shoulders back a maximum of .001 from a tight case, and with that setting, the bolt closes just fine, because as long as you have even a tiny amount of clearance all the way around a case, there is nothing to interfere with the bolt closing.

 

[fguffey]

Hey all, I am wondering how much to shoulder bump.

I have bump presses and I have non-bump presses; the difference between bump and non bump presses is the bump press is a cam over press. Very few reloaders know the difference between a cam over press and a none cam over press.

So: There is a chance you are attempting to bump your case with a press that will not bump. And then there is that other almost little know fact; it is not possible to bump once because the bump press bumps twice, once on the way up and again when the ram is lowered.

We now have a whole generation of bumpers, they believe they are moving the shoulder back as in 'bumping the shoulder back' and they insist they are using full length sizing dies and or dies that have case shoulder/case body support. Again; it is impossible to bump the shoulder back with a die that has full length body support.

I am not a bumper so I size the case by controlling the length of the case between the shoulder/datum to the case head. I off set the length of the chamber with the length of the case from the shoulder to the case head. The reloader should learn to determine the length of the chamber from the shoulder/datum to the bolt face first. A reloader that can not measure the length of the chamber from the shoulder to the bolt face can become 'fire formers'' not much skill required to become a fire former. All that is required is to be able to pull the trigger. After learning to pull the trigger the reloader must learn to measure the length of the case from the shoulder to the case head. Problem: The reloader must learn to measure before and again after as in the length of the case from the shoulder to the case head. The fire former need to understand the effect the chamber had on the case when he pulled the trigger. That puts the fire former on the trail to becoming a reloader that understands what a comparator is used for.

F. Guffey

 

[Comrade Terry]

 

[KenOath]

Bout .002” from slight resistance on close with a stripped out bolt.

Edit: If you have no resistance on close with stripped out bolt then you obviously don’t need to bump shoulder back, but can almost guarantee you’ll find one with some resistance..

 

[Bart B.]

I've seen nothing bad happen after bumping shoulders back .001" after first firing new cases with maximum loads.

If you can, so be it.

 

[fguffey]

I've seen nothing bad happen after bumping shoulders back .001" after first firing new cases with maximum loads.

If you can, so be it.

All a reloader is required to do to become a fire former is pull the trigger. I believe the reloader that aspires to become a fire former should learn to measure the length of the chamber from the shoulder to the bolt face first. I understand the old story about the firing pin driving the case forward to the shoulder of the chamber but the fire former should know the difference in length between the case from the shoulder to the case head and the length of the chamber from the shoulder of the chamber to the bolt face.

There is a chance chambering a new case into the chamber could be a bad habit.

F. Guffey

 

[KenOath]

There is a chance chambering a new case into the chamber could be a bad habit.

F. Guffey


Can you elaborate on the above please?

 

[M-61]

There is a chance chambering a new case into the chamber could be a bad habit.

How is this a bad habit and what does it do?
On the rare occasion I purchase NEW brass (that I do not have to turn into a 6.5BR or 30 BR) I'll run all of it it into the chamber. I find it kind of nice to know whether it fits or not. I'm not about to load it and then find out for whatever reason it does not chamber.
And 'bumping' a shoulder is NOT part of my reloading unless it is needed. Some do most do not. Some cartridges I have found even with so many reloadings on them I have lost count (222REM) I've never had to 'bump'. Others, for whatever reason, require a minor 'bump' on occasion.
That 222 I've been shooting long before 'bump' became a term.
All of this is my own experience in my own BOLT action rifles.

 

[fguffey]

Can you elaborate on the above please?

I have made gages that check the length of the 30/06 chamber, I have 20 gages that include gages that go from .012" shorter to .020" longer than a go-gage length chamber. I have 30/06 rifles with chambers that are .011 longer than a go=gage length chamber.

Same for the 8mm57 chambers: I have found 8mm57 chambers that are .004" longer than a field reject length chamber.

At the same time I have friends that built wildcat that experienced case head separation on 5 of the first 10 cases fired. They always wondered why that happened on some receiver designs and not others. Anyone that cuts a chamber should be able to determine the length of the chamber from the shoulder to the bolt face. There are some simple methods and or techniques, problem, I am surrounded by reloaders that insist 'it can not be done'. One day, without a gage I offered to modify a no-go gage to measure 30/06 chambers from go to infinity. The man with the 20+ 30/06 gages thought that would make one of his gages a gage that was not 'period correct'.

F. Guffey

 

[4xforfun]

Yesterday....My once fired 6.5-47L cases.....most fit the chamber without resistance and some have slight resistance. SO...I bumped. Now When getting the die set up I start with the die backed off and turn it down little by little. With the die backed off the brass will not fit the chamber and the shoulder moves forward. I turn the die down till there is almost zero resistance when closing the stripped bolt...maybe just a touch when the bolt is fully locked.

That is how it goes with every new set of brass .

Tod

 

[ireload2]

The best way to find your chamber length is to take a case with a shoulder location longer than your chamber. You can also expand a case straight to remove the shoulder entirely. Then size the case in increments until the stripped bolt will close on the FL sized case with one finger drag. Repeat with several cases to verify the length is exactly correct. Measure your cases and they will be the length you bump from.

 

[alinwa]

The best way to find your chamber length is to take a case with a shoulder location longer than your chamber. You can also expand a case straight to remove the shoulder entirely. Then size the case in increments until the stripped bolt will close on the FL sized case with one finger drag. Repeat with several cases to verify the length is exactly correct. Measure your cases and they will be the length you bump from.

go get 'im Boyd................A'gain......

 

[ireload2]

Not true at all guffy.
If you ever want to shoot the new case you must chamber it to fire it.

There is a chance chambering a new case into the chamber could be a bad habit.

F. Guffey

 

[Comrade Terry]

 

[okie]

Has anyone ever considered that he may just be f*#%ing with your mind????....

 

[BoydAllen]

I have seen new cases that stretched .006 when fired. While this sort of thing will ruin a case if done repeatedly the amount of damage done that one time has not been a problem. This is all in reference to a rimless case. The real surprise can be if you do a before and after measurement on a belted case. I encourage you to do that and come back with the results. Many years ago I knew shooters who were loosing belted cases after only a few firings. They chalked it up to "magnum pressures". The problem was that they were following the manufacturers' directions for setting their dies. If any of you have a belted magnum, some new brass and some fired brass, do a bit of measuring and post on this thread. As a reminder, we bump for only one reason, to create a little clearance. If we already have a little clearance, there is no need to move the shoulder. There is one thing that comes into this that some may not know. If you back off a FL die and adjust it down a little bit at a time, checking your shoulder to head dimension as you go, just before you get to the setting where the die comes into contact with the case shoulder the dimension will increase slightly over that of the fired case. This happens because of the sizing of the diameter of the body. Try it and see for yourself. That is why I recommend setting the die to a specific measurement rather than just backing it off so that the case is not bumped.

 

[Eddie Harren]

"There is a chance chambering a new case into the chamber could be a bad habit."