Shoulder Bump Question

[leclairk]

I’ve got about a thousand rounds of once fired Hornady brass from a previous gun in 6.5CM that measures 1.5315 base to shoulder. My new gun once fired Hornady brass measures 1.5335. Is there a way to only full length size the brass with my Whidden non-bushing die without bumping the shoulder since it’s already .002 back?

 

[Tokay444]

I’ve got about a thousand rounds of once fired Hornady brass from a previous gun in 6.5CM that measures 1.5315 base to shoulder. My new gun once fired Hornady brass measures 1.5335. Is there a way to only full length size the brass with my Whidden non-bushing die without bumping the shoulder since it’s already .002 back?

Is your die set to bump your brass back from 1.5335 to 1.5315?

 

[BeefyT11]

You could neck size only for this firing. If they will chamber freely in your new chamber. Pull your firing pin assembly and see if they chamber with ease. If not you'll need to set your full length die for that amount of shoulder bump.

 

[Bc'z]

Use a set of feeler gauges.
Start with .010 size and measure.
Did datum grow or stay the same?
I'm betting it's gonna grow a lil bit.
If measurement is longer than you original brass move to .008 feeler gauge, and so on with subsequent feeler gauges until desired measurement is achieved.
Also check measurement just above the web making sure your brass isn't to fat from the other chamber.

 

[RegionRat]

I forget if my Whidden die is meant to bottom out at SAAMI or if that over sizes as if it is meant to always have a gap. I have his dies in 308 and 6mm so I may have to go break them out next time to answer this the right way.... I would normally also suggest a variation on @Bc'z post by pointing out the use of either the sizing shims or the incremental shell holders designed to control bump. Redding calls them competition shell holders sets. However, they depend on the design of the typical sizing dies where they are about -0.001 - -.002" from SAAMI spec when bottomed out. So don't go all the way to zero where you are bottomed out if the Whidden dies are designed with a gap.

https://www.redding-reloading.com/online-catalog/35-competition-shellholder-sets

http://bulletin.accurateshooter.com/2015/10/sinclair-full-length-sizing-die-shims/#:~:text=When%20they%20need%20less%20bump,(one%2Dthousandth)%20increments.&text=Sinclair%20Int'l%20offers%20a,bump%20and%20sizing)%20in%20precise%20.

 

[Boatschool02]

Apologies up front if I'm misunderstanding the question.

As suggested above, recommend measuring & focusing on what it needs to be to allow a stripped bolt to close freely.
You may not need to push the shoulder back on the older brass much or even at all.
You can control that easily by backing the die out as necessary.
Perhaps start by sizing some of the newer brass and see if old brass will drop in similarly at the same die setting.
The FL sizing die does all kinds of good work for you at the base, shoulder, NSJ, neck, etc., even if not pushing the shoulder back very much. If the two chambers are already that much different, I would want to know that the older brass went through the same die as is working well with the new chamber.

 

[CharlieNC]

Partially seat a primer into an empty brass, chamber it and close the bolt such that it finishes seating the primer. Remove and measure to obtain the "zero" headspace dimension. Use this to know your desired bump length. Extremely easy, reproducible, and accurate.

 

[338 dude]

I’ve got about a thousand rounds of once fired Hornady brass from a previous gun in 6.5CM that measures 1.5315 base to shoulder. My new gun once fired Hornady brass measures 1.5335. Is there a way to only full length size the brass with my Whidden non-bushing die without bumping the shoulder since it’s already .002 back?

Just run them through your die if it set up properly for your chamber it will not push the shoulder back unless it is needed

 

[leclairk]

Awesome. Thanks guys. If I can get away with not bumping and they will still chamber I will go for it.
I would love to remove the firing pin but it appears to be a pain in the ass on a Savage Model 10 and I don’t trust myself that I won’t screw it up.

 

[Jennb]

You will need to size the necks anyways so just go ahead and full length size them. This way your case capacity will remain the same.

 

[D-4297]

If your Die is currently set for your rifles chambered brass , you should have no issues processing the shorter shouldered brass at that setting . On F/L sizing , some brass will "grow" in OAL as it is being re-sized . Like squeezing one end of a balloon , the brass will "flow" to the other end . Sometimes a little , sometimes more than expected . Then you get to trim , too . Another option may be to use a small base Die , to insure all the cases are reset to the good ole SAAMI specs at the base , and then re-check "Bump" length . Then F/L size .