In 223/5.56 it is common for competitors to load the 80 grain Sierra bullets for slow fire at 600 yards. Sierra says to seat them to 2.550" COL. It's 0.330" over SAAMI max, but that's because the ogive is so long its shoulder (where the ogive starts to depart the cylindrical bearing surface portion of the bullet) at the right place for a normal throat. The assumption is simply that you will load them singly and not from a magazine and then they will be fine.
One time I bought some HSM ammunition that used that 80 grain Sierra, but it was not seated to 2.550". It was seated to 2.230". HSM had figured out they could set the bullet shoulder below the case mouth (which this did) and it still functioned fine. You have to watch out for the "dreaded donut" forming at the neck and shoulder junction and ream it out if that happens, but it's no big deal. There is just a lot of bullet jump. But it seems to function just fine.
Berger found out, and I expect this applies to all long-ogive bullets and secant ogive bullets in particular, that in some rifles some bullets don't group well until the jump is over an eighth of an inch. The deep-seated HSM has a good deal more jump than that in a standard chamber, to no particular disadvantage on paper. It is still commercial match ammunition and works as well in my gun as any commercial match ammunition does.
The bottom line: determine what seating depth gives you best accuracy and use that for single-loaded rounds for precision, but don't be afraid of a long jump for magazine fed ammo.
One time I bought some HSM ammunition that used that 80 grain Sierra, but it was not seated to 2.550". It was seated to 2.230". HSM had figured out they could set the bullet shoulder below the case mouth (which this did) and it still functioned fine. You have to watch out for the "dreaded donut" forming at the neck and shoulder junction and ream it out if that happens, but it's no big deal. There is just a lot of bullet jump. But it seems to function just fine.
Berger found out, and I expect this applies to all long-ogive bullets and secant ogive bullets in particular, that in some rifles some bullets don't group well until the jump is over an eighth of an inch. The deep-seated HSM has a good deal more jump than that in a standard chamber, to no particular disadvantage on paper. It is still commercial match ammunition and works as well in my gun as any commercial match ammunition does.
The bottom line: determine what seating depth gives you best accuracy and use that for single-loaded rounds for precision, but don't be afraid of a long jump for magazine fed ammo.