Thread: Seating depth difference.

Hi guys,

I'm currently loading 140g ssts and 140g accubonds, The SST's need to be seated 2 full turns of the die deeper to chamber them. whats the go.? What can this effect? Speed? Havent chronied any yet just testing for accuracy and practice!
Cheers,
Tim

They will have a different nose profile and your seating stem is hitting a different place on the nose. If you measure from the base of the cartridge to the ogive of the projectile you will probably find they are the same.

The effect can be a higher (excess..) pressure peak if the projectile is now in contact with the lands. Mag length limit mostly stops this happening. COAL is not that relevant except to tailor to mag length limit. The most important measurement is base of the cartridge to the ogive (a la Stug). But you need to determine your max length from cartridge base to lands so you know your relationship of your loaded round's ogive to lands contact. Hope that makes sense...

Hornady has different seating stems for its dies depending on the ogive, maybe you need the right one?

Originally Posted by steven

Hornady has different seating stems for its dies depending on the ogive, maybe you need the right one?

I don't know of any manufacturers make seating stems that reach right down to the ogive? Correct me if wrong in Hornady's case. Sure some of them make different shape stems to accommodate the different shaped tips that standard projectiles and VLDs projectiles present and their purpose is to try an optimise the trueing up of the projectile at seating time.

Yes length to ogive are the same. So i'm probably not actually seating them deeper into the case, (using the same dies, RCBS for both loads) just the case of the seating stem picking up the projectile a bit further down the nose or something like that.? Both projectiles certainly have different profiles with the Accubond being far more barrel shaped.
Sorry if this all sounds dumb. Im very green to reloading!

Originally Posted by deepsouthaussie

Yes length to ogive are the same. So i'm probably not actually seating them deeper into the case, (using the same dies, RCBS for both loads) just the case of the seating stem picking up the projectile a bit further down the nose or something like that.? Both projectiles certainly have different profiles with the Accubond being far more barrel shaped.
Sorry if this all sounds dumb. Im very green to reloading!

Doesn't sound dumb - sounds like you have it sussed.

Get a bullet comparator and attach it to your vernier. In a pinch you can epoxy some nuts together.

Measure the projectiles from base to ogive. Then measure a loaded round from case base to ogive. Now you can work out how much of the projectiles bearing surface is held inside the case.

Seating the base of the projectile further down will cause more pressure...smaller expansion chamber. Seating the ogive too far forward will also cause higher pressure when you start "jaming" into the lands.

The way I do this is to use the hornady tool and modified case to find the lands in the chamber for a particular projectile, and then load 10 thou back, unless there is a specific reason not to (vld projectiles, or fine tuning group size).

Thanks for the replies guys good useful info. Cheers