Shoulder Bump

[22~308TargetShooter]

Loading for about a year now, and rounds are shooting well and I'm staying competitive in matches with my loads, but not really sure about this. I'm measuring a fired case with the Hornady headspace gauge or shoulder gauge and it's typically approximately 1.625, now I was taught to just try to bump back .001 to .002 in resizing. So I had everything set up and was getting cases coming out at 1.624 to 1.623 and thought Ok swell right on target. After seating I gave rounds another check just for kicks and then found the measurement to be 1.620 to 1.622, What the @!$& ? Am I doing something wrong or missing something ? Im turning out the overall length I want (measured to Ogive) and all, and rounds are shooting fine but am just perplexed as to the change. ???

C.D.

 

[potatoe]

I'd take a case that was fired and measure the shoulder. Then I'd seat a bullet into that case (you might have to size the neck to get the bullet to stay in the neck, but make sure you don't bump the shoulder) and measure the shoulder then. If it does change it would almost have to be something in your seating die, which I've never came across. Shoulder bumps can be a pain to measure with much degree of accuracy, take a few measurements every time.

 

[cmillard]

i think you have some things mixed up. i think you are treating OAL and shoulder set back as the same. i set up my dies with .002 setback. take a fired case (with primer removed--use punch pin and base) and place in wilson case gage. then run case into bushing bump die until my desired amount of bump is achieved then i lock the ring on the die. or are yo talking about the shoulder being bumped back further during the seating process?

 

[22~308TargetShooter]

Yeah, I'm getting shoulders bumped back a bit more after seating,

 

[243winxb]

What brand of seating die? To much crimp can bulge the shoulder or set it back. Very high neck tension on bullet seating may have an effect?? Chambering a round can set the shoulder back also.

 

[22~308TargetShooter]

Die's are RCBS .308 Competition Die Set

 

[cmillard]

if they have too much neck tension when bullet is seated, give jim carstensen a call (JLC precision--phone # listed on this site), he can modify them. or just get a forster bushing bump die and be done with it