When ordering a rifle set up for breechseating,is the chamber and throat different than when you shoot fixed ammunition. Thinking of one and ask because the bullet is set in front of the chamber when breech seating so would have to do some jumping if shot with fixed ammo.
Would this detrimental to accuracy?
I have a note into cpa but am trying to forge ahead.

calledflyer wrote on Jul 29^th, 2025 at 11:34am:

My question was are they different. I can see the throat would be but is the chamber ?
I understand what you are saying. 

Differences in chamber and/or throat specifications really have no effect regarding breech seating. 
The accuracy from breech seating comes from fully inserting the bullet so the bullet base is properly engraved by the rifling; which is well past the throat.
Some will dicker that the angle of the throat is important for better insertion of the bullet.
My experience is the most important factor for proper bullet insertion for accuracy from breech seating is having a breech seater that pushes the bullet into the bore (perfectly inline with the bore) and is perfectly aligned (not slightly angled sideways).
Also the breech seater must be adjustable to push the bullet into properly seat the bullet so the base is properly sealed so gases cannot cut around the side, to provide a consistent chamber volume behind the bullet so you always have consistent pressures.
If your breech seater pushes the bullet in slightly off angle the tapered throat will not center it. 
It will result in one side of the lands cutting into the bullet more than the other side which means it ends up out of alignment - and really impacts you accuracy.
So the priority is a good seater that pushes the bullet in perfect alignement.
Comaprison of one that did and one that did not resulted in a  6 points difference per ASSRA target when I did long term testing.

With BSing, the area ahead of the case, won't make much difference, other that what force it takes to BS. To much force, will distort the bullet. The base band needs to be at least .001 over groove dia. But, if your shooting fixed ammo, it can make all the difference in the world!

The std 32/40, has only a 30° angle ahead of the case, nothing else. A tapered or bore riding bullet, such as the Hudson bullets will align themselves in that type throat but, you'll have a lot of trouble getting a cylindrical bullet aligned in that throat.

For fixed ammo, you need a long taper, threw the lands to do that and a freebore also helps. You would size the bullet to fit .001 over the freebore or size it .001+ over  the groove diameter w/o the freebore.