Measuring bullet seating depth to the lands - do I have this right?

[canoetrpr]

Do I have this procedure right for getting the correct OAL for each of my bullet types to the ogive:

I picked up a Sinclair bullet seating depth tool along with a bullet comparator and insert for .30 calibre. I've followed the instructions and for each bullet type:

- Took out a sample bullet and measured its OAL
- Did a measurement with the bullet touching the lands and then the fired case

Now I must add the bullet length for each bullet to the measurement on the gauge taken for that bullet. That is the OAL for that particular bullet that will seat it to the lands. Now to eliminate bullet to bullet variation, I need to convert that to a OAL taken at the ojive fot that bullet:

So for every one of the bullets that I used in sizing, I should construct a dummy round seated at a depth that gives me the OAL that I measured for that bullet to bullet tip. Now I can put the bullet comparator on the caliper an measure each of these dummy rounds from cartridge base to ojive. This is my max OAL for that bullet type to the ojive.

Anything I am missing?

 

[Kelly Timoffee]

Way easier to make a dummy round and measure base to ogive, done!!!

You can partially size the neck to hold the bullet snug , use the magic marker to find the lands on the bullet when they touch once you insert and remove the dummy round.

 

[canoetrpr]

Now that I've done it with the tool, sure sounds like it! I bought the tool cause I thought it would be more precise. Now I wonder if I shouldn't have bought a collet die instead

Now that I have the tool, I'm sticking to it! Still waiting for confirmation that I need to make a dummy round with the bullets I used to get the dimensions.

 

[DMS1]

Way easier to make a dummy round and measure base to ogive, done!!!

You can partially size the neck to hold the bullet snug , use the magic marker to find the lands on the bullet when they touch once you insert and remove the dummy round.

I do this also, a few times and take the average, but find that it is still off a bit, since the bullet slides and the extractor pulls the bullet against the throat. Once I think I know where the lands are, I load a bullet .010" longer, put marker, check for rifling marks, clean marker, press lower, check again. I do this out doors with the rifle pointed at a backstop. Not a fan of loading live rounds repeatedly in the house....

 

[Kelly Timoffee]

That is also a problem I ran into so what I wound up doing was sizing and seating a dummy round like normal , seating out far(bolt doesn't close)and press the bullet deeper in very small increments until the bolt does close, then do that magic marker trick, time consuming but the most accurate way I have found that works for me.

I do this also, a few times and take the average, but find that it is still off a bit, since the bullet slides and the extractor pulls the bullet against the throat. Once I think I know where the lands are, I load a bullet .010" longer, put marker, check for rifling marks, clean marker, press lower, check again. I do this out doors with the rifle pointed at a backstop. Not a fan of loading live rounds repeatedly in the house....

 

[Shibby!]

I do this also, a few times and take the average, but find that it is still off a bit, since the bullet slides and the extractor pulls the bullet against the throat. Once I think I know where the lands are, I load a bullet .010" longer, put marker, check for rifling marks, clean marker, press lower, check again. I do this out doors with the rifle pointed at a backstop. Not a fan of loading live rounds repeatedly in the house....

I do it all with dummy rounds. I do not feel safe loading live rounds in my gun at home. In fact it's opening the door wide for issues to happen. You are lucky to have a backstop, but many others are like me and do it in their basement.

A good rule to follow is NEVER load live rounds unless you're at a range and muzzle pointed downrange. Clearly mark your dummy round so it's obvious which one it is.