How critical is case length when breech seating? Is SAAMI spec. required?
Or, is several thousandths short OK as long as each case is the same length?
My personal experience favors the latter. ? Thoughts ?
Thanks.

When you breech seat the bullet, it is always pushed in to the same depth so the case volume behind the bullet will be the same.

Yes if all your cases are of the same length.

However a shorter case will not fill up the space as much and you will have a bit larger case capacity (volume in case plus the volume in the barrel leade behind the bullet).

So to have the exact amount of volume you need to have cases all the same length.

Picture of changes to a group size by slight changes in case volume using an adjustable seater to change case volumes slightly.

It does make a bit of difference but maybe not enough for some people.

Unfortunately Russ Weber is not here anymore, because he would verify it since that is why he made adjustable breech seaters.