If you send a couple of bullets to Lee, they will make a seating stem to fit it.
I don't know what (or if) they charge for that.
Before you go to that trouble, you might want to pull the seating stem out and see how it fits your bullet's nose. You might find it gunked up with bullet lube and cleaning it out once in a while will make it seat with better consistency.
[email protected] pointed out an important fact. If the bullet is tilted, usually shoving it into the case straightens it out, but if the lead deforms or it doesn't get perfectly straight there might be some variation in overall length. Setting the bullet straight on the case will probably take care of this, but also, try this trick:
When seating, just after the bullet nose contacts the seating stem, lower the ram of your press just a fraction of an inch, then seat the bullet the rest of the way. See if that helps.
But here is the most likely cause of OAL variation: The bullets themselves have slightly different nose shapes. Look carefully at the profile of several bullets. Measure the actuall length of the slugs. Lastly, paint the bullets' nose with a felt-tip marker (dry-erase type) and, after seating them see where the marking from the seating stem is in relation to the bullet nose.
The seating stem's "socket" should contact the entire surface of the bullet, but this rarely happens. Usually there is a ring of contact. If there is a crescent of contact, then something is off-center. If the ring of contact varies in position, your bullet's have differently shaped noses and will never have consistent OAL
Do some detective work. It's fun. Especially when you solve the puzzle. It's like hitting your head against a brick wall. It feels really good when you stop.
Lost Sheep.