Question on shoulder bump

[HighnDry]

I understand that most people bump the shoulder back .002".
My question is what should I do with mixed brass? Both were shot out of my rifle, but a barrel change was done so the measurements with the comparator are different.
On the old barrel, the comparator measurement is 1.558 and on the new barrel, the comparator measurement is 1.561. Should I just do a bump to 1.558? If so, how do you know if you got to the shoulder with the die on a zero shoulder bump?

Thanks!

 

[Justin Crossley]

I would only bump to 1.560" myself. Don't bump the shorter cases at all until after you fire them in the new barrel.

 

[HighnDry]

So, if I just set the die to 1.560 and run all the cases through (because I still need to size the neck with a bushing) that should do it?
Excuse my ignorance

Thanks!

 

[packer58]

Shoulder bumping IMO is a function to provide reliable chambering of the loaded round and not overworking your brass in the process. It also tightens up the fit between chamber and cartridge case.
It sounds like in your case you have cases that were fired in chamber (a) (old barrel) and chamber (b) (new barrel). I use a Redding body die to bump shoulders but you may not have one and it doesn't really matter that much... so.... grab a few of your cases that were fired in the new barrel and bump them to a level that your bolt will close without resistance, work the shoulder down slowly and you'll feel it when its right. Once you get your die set just run all your brass, you might find that the brass fired in the old barrel may be close to the bumped brass.......or close enough.

 

[Pickettpuncher]

Depends on your application and what you’re expecting to achieve. I personally don’t mix brass unless it going thru my AR. I also don’t expect my AR to shoot 1/2 moa. I didn’t build it for that. I want functionality. Now my hunting rifles, absolutely. I don’t use mixed brass in those. I also strive for much better accuracy. But the thing about mixed brass is case capacity. You run the risk of having both pressure issues and not getting the accuracy

 

[EdP]

The chamber of your new barrel is a bit longer than the old so set your die up for the new barrel. Run all the fired brass through, because as you said, even the brass fired in the old barrel needs to be sized, but it will be a bit shorter at the shoulder until it has been fire formed to the new chamber.

 

[packer58]

Pickett has a good point regarding mixed brass (manufacturer and headstamp)....
I guess my assumption of the OP's meaning of mixed brass was same headstamp just fired in different chambers.

 

[Ucsdryder]

For a hunting rifle I would do at least .002. A dirty chamber doesn’t give a lot of room.

 

[Vern400]

You got a new barrel with a longer chamber. You could potentially just chamber and check the empties for headspace with the bolt. If the bolt closes with 2 fingers LOAD IT! Get it all the same, and THEN go back to bumping 2 thou. I got 2 rifles same caliber, different headspace and it got me in trouble once. Not any more because I check 100% now for headspace dimension. And don't mix the ammo.

 

[longbarrel]

I bump the shoulder just enough for smooth chambering, close to zero effective headspace.

 

[35WhelenAI]

Loading for a 300 Winchester magnum, I do the process described above in post #4 and mentioned again in #10. Just touching the shoulder with the die until the round chambered smoothly and reliably. My feeling on hunting rounds is err on the side of a bit more shoulder bump versus too little.

 

[wapitibob]

Take the guess out of it; use a candle flame to smoke the shoulder and chamber it.

 

[35WhelenAI]

I like the idea of the candle. However, how is it less guess work to bump the shoulder back with the die in increments until the case chambers freely? There's no guess about it, it chambers freely or it doesn't.

 

[Hunter3721]

I would Full Length Resize, shoot those and then set back .002 -003. Ed