OAL at Ogive something not right

[chesty for president]

This is whats going on may run a little long. I sacraficed a 7mmSAUM case to seat a bullet into for getting the OAL of a loaded round. Well I did that a couple of times with the same bullet and I kept coming up with the same measurement which im guessing is good because it was consistant. So then I proceed to my Forstner Ultra Micrometer bullet seating Die at which point I pull the bullet out of the modified case just a bit and make adjustments to the die until it reads the same seating debth as it did after being pulled out of the action. Heres where the confusion comes in. When I take a primed, powdered case and try to seat a bullet in there it comes up .010 longer .050 shorter almost every single time (never exactly the same as the test round). Im not sure if the brass is that "springy". I am no where near a compressed load with 59.5 grains of 4831. Im kinda lost on this thing. All measurements are at the ogive. As a matter if fact some of the measurements are slightly under or over the measurements that were aquired using the modified case setup, even though the cases are a 1.20 a piece lol. Any advice would be very welcome and greatly appreciated. Id like to get out shooting this weekend but I dont want to be flinging rounds down range for no reason other than feeling recoil.....Thank you again.


Very Respectfully Submitted

Semper Fidelis

 

[Keith Glasscock]

How does the neck tension "feel" compared to your test case? I know that I have to readjust my seating die for different neck tensions.

Other than that, the only thing I can think of is the tip of the bullet impacting inside the seater stem. If that is the case, the bullet is being seated by its tip, and the ogive measurements would be all over the place.

 

[pmarauder]

How does the neck tension "feel" compared to your test case? I know that I have to readjust my seating die for different neck tensions.

Other than that, the only thing I can think of is the tip of the bullet impacting inside the seater stem. If that is the case, the bullet is being seated by its tip, and the ogive measurements would be all over the place.

Those are both great answers to your potential problem....
First of all.... how are you obtaining your ogive measurement on a seated round? I believe the sinclair SS inserts on your Comparator body gives the most accurate measurement. (they are a tapered insert)
Second.... are you sorting your bullets by bearing surface? or base to ogive? IN a 100 count box of the 180 hybrids.... you will get different "piles " when segregating them within .001" of bearing surface. This will effect where that ogive will make contact with your seating stem inside the Die.
Third.... Neck tension is critical. Are you turning your necks to a specific thickness? Nosler brass is very good on neck wall thickness, but if you get a piece of brass with a thick spot on one side......this will create a pinch point and result in tighter neck tension.....which in turn will result in the bullet not seating as deep on the first press stroke. (you may have to double pump the press"
I would sort my bullets by bearing surface if I were you, and focus on your neck tension. Make your brass as consistent as possible. I would run .002" of neck tension, and brush your inside case necks with a stiff nylon brush.
Are you ultra sonic cleaning in-between your firings?