so after loading up several thousand rounds of plinking ammo and then really getting down to loading some quality hunting ammo last year. i got to reading a bit more to see where i could streamline my process a bit and or make sure there weren't any small details i was overlooking. it came to my attention that maybe i should try out one of these hornady oal gauges so that i could start measuring my bullets at the ogive. so now i have one of these things and im kinda at a loss of what to do with it now.

what i have been doing is just measuring to the tip of the bullet with my calipers and going with it at the book suggested oal. it has worked out fairly well so far as i was able to consistantly achieve 3/4" groups at 100 yards out of my model 70 270wsm with a few 1/2" groups thrown in on good days. iirc the nosler manual has an oal for the 150nbt's at 2.550 so thats what i have been putting them at to the tip of the bullet. now i have this thingy and im wondering if the book oal is measured to the ogive or to the bullet tip? i measured some of my loaded ammo and recorded the ogive measurement and can duplicate what i have now but should i actually be loading the ogive all the way to 2.550?

All load data is giving a length based on measuring to the tip of bullet. Measuring to the ogive is more consistent as bullet tips can be deformed from bullet to bullet. Really though the slight difference cause by the bullet tips being deformed makes no difference. The ogive is the first thing to contact the rifling. From your description it sounds like you only have the bullet comparator that attaches to the caliper.

You should be using the OAL gauge with the modified case specific to your cartridge and then you can find out the distance to your rifling.Once you know the length that the bullets ogive contacts the rifling then you can start experimenting. Some rifles like to shoot their best with the bullet a certain distance off the rifling. Once you find that sweet spot if it exists the bullet comparator is a great tool. No matter the bullet shape you can can set the ogive the same distance off the rifling. I have even encountered different lots of the same bullet with the ogive in slightly different places. Had I just went with the bullet tip mesurement I would of been a different distance off the rifling. Might make a difference might not.Granted not every bullet will shoot the same but most times if your rifle like the bullet a certain distance off the rifling it will apply to nearly all bullets you try.

Using just the comparator as a measuring device is really not necessary. Once the die is setup your seating depth is unlikely to change. Measuring to the tip is fine the slight pluses or minuses are the bullet. If it changes drastically then you can check with the comparator. I check the first five cartridges for length I load after setting the die. If they are all good I run them and check every fifth one after that.

When I use the gauge, I take the Hornady modified case with the bullet I wont to load in it. Slip the OAL into the chamber and then move the bullet up to where it starts to engage the rifling and tighten OAL down. Remove the gauge and bullet, then with the ogive measuring device in your calipers you measure the length. I find about 4-6 off the lands works for me.