6mmBR shoulder bump causing issues??

[Exercion]

So I see a couple other shoulder bump threads and didn't want to hijack. So here we go...

I normally neck size only for my 6BR (Savage Target Action with Broughton 5C barrel). But having read advice to full length size with a small bump of the shoulder I figured I'd give it a try. However, when I bump the shoulder back 0.002", the rifle does not want to cycle at all, even on empty/sized cases. I can close the bolt, though it is not easy, and opening again is a bear.

I'm using Redding bushing dies. I also have a body die, just hadn't tried it in this experiment, since sizing with one die not two is preferable. Any thoughts on what might be going on here? Oh yeah, and I'm using Lapua gold box brass, and the same bushing I use for neck sizing.

Eric

 

[B23]

Have you tried bumping the shoulder back another thou to see if that cured your problem?

 

[JFrank]

I love these shoulder bump threads

 

[Mark W]

How is the .002” bump being measured. If it’s too far down the shoulder, the neck/shoulder junction could actually be longer with a small bump. I like to measure somewhere as close to the middle of the shoulder as possible.

 

[tmwinds]

When you move the shoulder back by bumping the brass must move somewhere. If the body is being fully supported and sized by the die the displaced brass will normally move to the neck and cause it to become longer. Check the length of a piece of unsized brass vs the length of a piece of sized brass. If your brass was near max before sizing it may now be over max and causing the neck to crimp and stick in the barrel. If this is the problem your brass will need trimming. Also, if you are sizing the body and the shoulder is not actually being bumped the shoulder will move forward. You will need a good comparator and calipers to determine if this is the problem.

 

[Lefty Trigger]

Measure against a case that will fit and see where the issue is. I'm finding that I have a few cases that will not size down enough near the base causing a tight bolt, the cure is to run them through a .308 small base die first then resize with the BR die,... seems to work out. BTW this was not an issue with my old barrel just my new Shilen, tight chamber??

 

[brxbrad]

Small base size then shoulder bump....I use a 243 small base sizing die on my BRX brass otherwise they won't fit in my Wilson seating die and are hard to bolt over. All it takes is .001 to fat and things aren't happy.

 

[Falfan2017]

If you aren’t sizing the body it’s likely the body towards the base is too fat. Saw that before on a guy who was just neck sizing. Do you have a piece of virgin brass to measure the body at different places compared to a fired one that won’t chamber?
I suspect if you got a full length sizer you wouldn’t go back.

 

[mikecr]

I'm using Redding bushing dies. I also have a body die, just hadn't tried it in this experiment, since sizing with one die not two is preferable. Any thoughts on what might be going on here?

Is the Redding a bushing neck sizing only die, or a FL bushing die?
You can bump shoulders with the body die. You'll need a gauge to measure & repeat your bumps.
Normally, no more than 1-2thou of bump (from interference) is needed to chamber well in a bolt gun.

 

[Steve Ladino]

So I see a couple other shoulder bump threads and didn't want to hijack. So here we go...

I normally neck size only for my 6BR (Savage Target Action with Broughton 5C barrel). But having read advice to full length size with a small bump of the shoulder I figured I'd give it a try. However, when I bump the shoulder back 0.002", the rifle does not want to cycle at all, even on empty/sized cases. I can close the bolt, though it is not easy, and opening again is a bear.

I'm using Redding bushing dies. I also have a body die, just hadn't tried it in this experiment, since sizing with one die not two is preferable. Any thoughts on what might be going on here? Oh yeah, and I'm using Lapua gold box brass, and the same bushing I use for neck sizing.

Eric

 

[Steve Ladino]

Sounds like the case area above the extractor cut is enlarged and bumping exaggerates the oversize there.

 

[CharlieNC]

Always keep a new unfired case (or one you know has been prepped properly and fits just right) as a standard from which you can measure all potential problem spots. Or you can end up chasing your tail trying to fix what is not the problem, and creating new ones.

 

[Exercion]

Sounds like the case area above the extractor cut is enlarged and bumping exaggerates the oversize there.

Close! After measuring virgin brass, loaded rounds that cycle, deprimed cases that cycle, sized cases that won't cycle and finding nothing that measured wrong, I had the idea to try different cases in a different Savage target action rifle. Everything cycled flawlessly. Looked closely at the bolt in the rifle I'm fighting and the extractor looks worn and or damaged, especially compared to the other. So it's looking like a new extractor and assorted parts are on order.

Eric

 

[miningshawn]

https://www.midwayusa.com/product/4...roduct-shipped-today-product-description-link

With free shipping no less.

 

[Exercion]

https://www.midwayusa.com/product/4...roduct-shipped-today-product-description-link

With free shipping no less.

Thanks, already have it, that's how I have been measuring my cases

 

[miningshawn]

Thanks, already have it, that's how I have been measuring my cases

I was measuring cases for a very long time without this tool. I was actually using a cut-down piece of aluminum tubing with a chamfered shoulder.

With all of the threads asking about neck size, shoulder bump, case sizing, etc... I thought it wouldn't hurt for the next poor fella who has a pair of calipers and is wondering how to get .002 shoulder bump. Not meant as a flame or a slam, sorry.

 

[Ghansen]

I use the Alex Wheeler method for finding seating depth, except without a bullet to find just enough bump when resizing

 

[Webster]

So I see a couple other shoulder bump threads and didn't want to hijack. So here we go...

I normally neck size only for my 6BR (Savage Target Action with Broughton 5C barrel). But having read advice to full length size with a small bump of the shoulder I figured I'd give it a try. However, when I bump the shoulder back 0.002", the rifle does not want to cycle at all, even on empty/sized cases. I can close the bolt, though it is not easy, and opening again is a bear.

I'm using Redding bushing dies. I also have a body die, just hadn't tried it in this experiment, since sizing with one die not two is preferable. Any thoughts on what might be going on here? Oh yeah, and I'm using Lapua gold box brass, and the same bushing I use for neck sizing.

Eric

Hot loads???

 

[Webster]

When you move the shoulder back by bumping the brass must move somewhere. If the body is being fully supported and sized by the die the displaced brass will normally move to the neck and cause it to become longer. Check the length of a piece of unsized brass vs the length of a piece of sized brass. If your brass was near max before sizing it may now be over max and causing the neck to crimp and stick in the barrel. If this is the problem your brass will need trimming. Also, if you are sizing the body and the shoulder is not actually being bumped the shoulder will move forward. You will need a good comparator and calipers to determine if this is the problem.

There is normally .045-.055" space to for the neck above the reccommended trim length in reloading manuals. Custom reamer may be different? Look at a reamer spec. or chamber spec.

Clymer reamer spec. 6BR over all length 1.570" Reloading manual trim length 1.560".