300 win mag brass

[243winxb]

300wm HS off belt there is no shoulder HS for belted cases

SAAMI lists the case head to shoulder datum length. Its NOT headspace.
The shoulder has to blow forward to fill the chamber. This stretch, if excessive, may damage brass on the 1st firing.

The OP at the link is measuring case head to shoulder datum.

 

[kevinbritvec]

My attempt at a solution to your problem would be to load the rest of the Lapua 300 WM brass seated long enough for the bullet to touch the rifling, thereby fire forming those cases to your chamber. Obviously, your powder charge will need to be reduced.

Unless you have a custom tight neck chamber in your rifle, turning Lapua case necks is both a waste of time and counter-productive IMO.

 

[243winxb]

Bullet jam, may help, good idea, as said above. Neck tension/Bullet hold, needs to be high. Use long heavy bullets. Fast burn rate powder, per data.

But the powder charges should not be to light. A light load, on firing, may expand the case body and pull the shoulder back
. (Shorter, head to datum.)

powder charge will need to be reduced.

Near maximum should be used, imo.

 

[Jeff Porter]

300wm HS off belt there is no shoulder HS for belted cases

Yeah but let that shoulder blow out too far … you will have problems. Never reach the belt.