shoulder bump

[rebs]

If fired cases measure shoulder at 1.460 then bumping .002 would be 1.458 is that right ?

 

[JLT]

Correct. If it's once-fired, it may be premature to bump the shoulder. It often takes two or three firings to fully form your brass to your chamber.

 

[Coyotefurharvester]

Size brass to chamber correctly and hold bullet. 0.002 may not be enough clearance in some chambers or gas guns. First determine what needs sizing. Body, datum, neck.

 

[K22]

That's correct but .002 may be too much or too little depending on the rifle, age of cases, annealed or not annealed, brand of cases, etc.

 

[EGBrown]

After three firings, remove fire control from your bolt. Bump shoulder on brass just enough so that you can close bolt with minimal effort using one finger. Some people verify each sized case with this method. I normally find this length and set my seating die to match.

 

[rebs]

Thank you guys for the help

 

[JEFFPPC]

Thank you guys for the help

Rebs you received some good advice. I will through in, Don't overcomplicate things. That seems to be a popular pastime on forums. Oh, one more. Don't get obsessed with numbers....Your targets tell the truth, if you ALWAY shoot over flags.

 

[nksmfamjp]

If fired cases measure shoulder at 1.460 then bumping .002 would be 1.458 is that right ?

How are you measuring that. Bump is measured as how far you are moving the datum circle towards the case head.

 

[RegionRat]

@rebs
Start with a quick study of the SAAMI spec print and learn to track the following.

Neck diameter virgin, and fired.
Diameter of the shoulder to body virgin, and fired.
Diameter at the 0.200 line virgin and fired.
Case length virgin and fired.
Shoulder datum is a comparative value unless you "zero" the gages on a GO-Gage, but record those virgin and fired dimensions too, as you mentioned above.
ETA: I encourage folks who are beginners to own the GoGage for their favorite rifle calibers.

Now take all of that same list after FL sizing, but as the others have stated wait to FL size till you find you can't close the bolt easily on a small number of cases with several cycles as a study, then size and record. That means you neck size only till you feel you cannot close the bolt on fired brass.

This study will take you from entry level needing help, to answering questions after you have done it for several different calibers and rifles. It gives the student an insight into how brass moves, as well as how their dies and chamber are either going to work together or not.

The majority of the times with common calibers and casual activity, brass, chambers, and dies will work out so you are happy. Every now and then, they don't but we want you to learn how and why, and to be in control of your outcome if there is ever any trouble.

Remember, some of these values will require a four decimal point measurement, some will be okay with a regular caliper to the third decimal. In general, in causal activity the lengths are from a 6" caliper, but the diameters will require a micrometer and some skills. YMMV

 

[JFrank]

I’ve gone around the barn on this subject more than once, sizing a fully formed case enough to chamber a round isnt rocket science but it takes a bit more sizing to eject a tight round. Guys tend to forget that part, preference would go to stripped bolt closer plus a couple thou.