Measuring O.A.L. Question

.257roberts

Hello everyone, My question is, when measuring O.A.L., will there be a different measurment with different bullets of the same caliber? I'm trying to get the O.A.L. in my rifle with a home made device like the one Stoney Point sells and a Hornady Lock-N-Load Bullet Comparator. My measurments are only a difference of .004 between a Sierra 75gr. HP and a Nosler 100gr. Ballistic Tip, should there be any difference? Thanks Robert

bpost

Yes; there will be a difference in OAL between bullets from the same box! The bullet seating stem contacts the bullet at point X. Each bullet type and weight has a slightly different point shape. therefore the contact point X will be different for each bullet.

.257roberts

If I was going to load my bullets .010 off the rifling, is there a certain amount of + or - that is acceptable? If not, what would I need to do to get everything to match?

JustC

buy the sinclair OAL tool. It is the best tool I have used.It will let you know the casehead to tip distance for your chamber. That measurement, coupled with the comparator from sinclair will give you a perfect measurement for casehead to ogive measurement. This is the correct way to set OAL,....Or should I say casehead to ogive. The OAL matters little,..since tips vary in length. The casehead to ogive is the real number you want.

Bullet tips vary in length,..and will show measurable discrepancies. The ogive measurement will remain constant.

dcs shooters

JustC hit it right on the "ogive" [;)]

sandwarrior

.257roberts

+3 on the Ogive.

Also, if you don't have the tool from Sinclair yet, you can do all of your measuring with one bullet and you should come out the same with all the bullets. Just find the ogive of one bullet and if uniform the rest should be in the same place. Remember not to go by the tips as they are usually not uniform.
For instance: Say you're loading Berger VLD's that need to be pushed into the lands. Using the dummy case that screws onto the Stoney Point tube/rod measuring device, drop one bullet into the mouth of the case. Measure one bullet to the lands. Add .005" or .010" as necessary to get the lands to mark the bullet. Measure from the base of the bullet to the front of the mark. Take the difference between the OAL and the point on the ogive where the lands hit. That should be your ogive measurement. Every bullet you do this with should have the same distance from the base to the front of the mark. If the bullets are uniform to that point, as they should be, you will get to exactly where you want to be. If you want to back it out of the lands then you turn in your seater until the OAL is back the amount it should be. It helps to know the thread pitch of the seater then you can mathematically figure how much you need to turn in or out the seater.

The comparator is easier because you can set your die using it and not measuring each different bullet this way, that you use. You just measure the case with the bullet. This is just in case you don't have one or want to buy the comparator.

.257roberts

Thanks for all the help fellas. Going to have to check on some more equipment I.E. some Sinclair products. Thanks again, Robert