Seating depth

[Curtis]

If I make a drastic change in seating depth in an already established (safe) max load, do I need to "work up" to max load again because of the change in case volume?

Curtis

[Ricci Price]

If you are coming out with your bullet, I would say yes because you are getting closer to the lands in the barrel therefore creating more pressure in the chamber some guys like to seat into the lands for increased accuracy but they usually back off of the charge to do so.If you are going into the bullet I would'nt be as concerned ,just my opinion,BUT!!! what I do may not be safe for your gun(just covering my ---)

[Curtis]

Thanks Ricci.  I should have noted in my original post that the throats in most of my barrels are so long that I can't possibly reach the lands anyway.  I was thinking more in terms of case volume change.

It is true as you say that you need to either back off the charge or give the bullet a "run" at the lands.

Curtis

[MickinColo]

Curtis,

I’ve experiment with the OAL of all my cartridges. As a general rule I work from the maximum OAL of my chamber - .005 0r .010 back down to the reloading manuals suggested OAL. I check the chamber with a Stoney Point O.A.L. Gage. In any number of round/bullet combinations the bullet is too far out of the case throat at Maximum over all length for any practical reloading purposes let alone the restrictions the length of the guns magazine plays.

As I test loads of various lengths I may not find any sign of pressure problems on the cases themselves, but I will see changes in bullet speed on the chronograph and changes of impact points on the target. I’m not sure if these changes are brought on so much by case volume issues (I’m sure it plays a role in some cartridge/bullet combos) as they are by changing the bullet jump timing. In any case the internal ballistics change with the OAL, sometimes very little, sometimes a lot.

If I’m ever in doubt about potential pressure problems, I don’t hesitate backing off the powder a little.