Dpms LR-308 Headspace changes after chambering.

[cerralvo78]

Hi
I have been reloading for the last six months
After performing OCW I have found my perfect load on my LR 308 DPMS 24"

Varget 43.2gn, lapua brass, WLR primers and 168 SMK
COAL 2.230 (base to ogive)
Headspace 1.619"
This gave me 3 shot group .297" @ 100 yards(look at picture)

My question is about headspace
Here is my data;
Lapua new brass Headspace 1.615"
Lapua once fire headspace 1.621"
I bump shoulder .002" to bring it to down to 1.619"

I notice that if a chamber a dummy sized round(headspace 1.619") and then I ejected the ammo, the shoulder goes back to about avg 1.615"

should I bump back shoulder to 1.615" or leave it at 1.619"?


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[FLIGHT762]

Most autoloader shooters bump shoulders from -.003"-.005" to be sure you get easy chambering. Bolt gun shoulders are usually bumped back-.001"-.002" due to the stronger camming action of a bolt gun..

 

[cerralvo78]

Most autoloader shooters bump shoulders from -.003"-.005" to be sure you get easy chambering. Bolt gun shoulders are usually bumped back-.001"-.002" due to the stronger camming action of a bolt gun..

Thanks.....But my question would be should I bump back base on my fire form headspace( 1.621") or bump back from chamber headspace(1.615") ??

THANKS

 

[FLIGHT762]

Your Rifle will let you know how much to bump. As long as the ammo chambers and easily EXTRACTS an unfired round. You can determine this by loading a few dummy rounds (no powder or primer) with varying shoulder bumping. You will find at a certain point, when the rounds extract easily without difficulty, you're good. You my be there already.

 

[cerralvo78]

THANKS FLIGHT762!!!
i HAVE DONE THE DUMMY ROUNDS SET THEM AT 1.619" THEN AND AFTER I CHAMBER THEM IT GOES BACK TO 1.615
BOTH OF THESE CHAMBER OK
SO SHOULD I LEAV IT ALONE AFTER FIRE(1.621") OR SHOULD I BUMP IT BACK DOWN TO .002" OR SHOULD I BUMPED A .001" BELOW THE AFTER CHAMBER SIZE (1.615")

THANKS AGAIN

 

[gunsnjeeps]

I ran into a similar quandary with my NM A2's. I size to what the chamber sizes them to. My logic was no.sense working the brass in two or three steps and it was sized enough to fit any chamber.

 

[cerralvo78]

Gunsnjeeps
That make a lot of logic to me!!