Making the most of the Hornady OAL gauge

[Pond, James Pond]

I have bought the Hornady OAL gauge and have used it to take "distance to lands" measurements on the 3 .30 cal bullets models I presently have.

Because I have a mag fed bolt gun this is perhaps less of an issue, but as I have been careful to be spot on with powder charge weights, I should do the same with COAL.

Using the Hornady kit I can seat bullets according to the height of the ogive, rather than the OAL to the tip of the bullet. I understand this is better in giving more consistent values because of mild differences in the curve of the ogive in manufacturing.

It therefore follows that I will need to adjust and measure each seated bullet in the seating die to see where the ogive is in relation to the case mouth, rather than adjusting the die to a given OAL based on COAL and then just seating all the bullets in my batch.

Is this correct?

If so, it seems it will make this part much more time-consuming, but presumably I will feel the benefits in my shooting.

Right now, seating my Amax bullets to be max mag length would put them 0.035" off the lands.

[cryogenic419]

I got the same gauge this last December. The way I transitioned is after I used the gauge and got a measurement from the rifle, I checked a loaded round I already had to see where that was in relation to the measurement from the rifle. I adjusted the die from there depending on the measurement, seat a bullet and check with the gauge. My understanding of it is its just like checking overall length with calipers, except you are measuring from a different point on the bullet and the comparator attached to the calipers. Once you get the die set for the new length its pretty much set it and forget it. The OAL lengths I was measuring the old way were really never that different from eachother. Now that I measure them with the comparator insert the lengths are pretty much identical. I'm using Sierra and can't say the same for other brands as I have not tried them but I imagine all your higher end bullets are gonna be pretty consistent

[steve4102]

It therefore follows that I will need to adjust and measure each seated bullet in the seating die to see where the ogive is in relation to the case mouth, rather than adjusting the die to a given OAL based on COAL and then just seating all the bullets in my batch.

I think you are making to much work for yourself here.

Use the gauge to find the Max OAL for your rifle and selected bullet.

Use the gauge to seat the bullet your desired distance from the lands measuring the same way you did to find Max OAL. I'm guessing you measured from case head to ogive, am I correct?

If you really want to get technical you would measure from the datum line on the shoulder to the Ogive of the bullet. ...but you don't want or need to do that. Just measure from the case head to the ogive, just the way the Gauge was designed.

Measuring head to ogive will still net you some variations in OAL, if it's less than .005 I wouldn't worry about making adjustment. That little bit isn't going to affect accuracy or pressure as long as you are not already pig-jammed into the lands.

[Rimfire5]

When I measure seated cartridges from base to ogive with my Hornady unit, the variation is usually +/- 0.001 with high grade bullets. I measured the chambers for all my rifles and then used the measuring tool to monitor the base to ogive measurements on loaded cartridges.
At first, I measured every seated round and found that the variation was minimal. Now I measure when I am setting up the dies and once the setting is where I want it, I am now confident that the results will be consistent.
I have noticed that my group sizes are more consistent since I started using the base to ogive measurements.

James, the chamber measure tool is handy for checking barrel erosion too.
I remeasure the chambers in my rifles every 1000 rounds or so. I have found that some calibers erode by as much as 0.015 - 0.020 during that amount of firing depending upon how hot a load you generally use. That amount of erosion would change your overall cartridge length setting if you were trying to stay at 0.020 off your rifling.

My old .308 eroded 0.090 after 6300 rounds and at that time I began to see some degradation in accuracy, even though I was moving the bullet seating out to keep the bullet within 0.020 of the rifling.

[Pond, James Pond]

Today I used the gauge to help seat bullet in my OCW string for N135 the Hornady 3037 bullet, all but the last two steps in the string for the Lapua 155gr Scenar and just a bunch of Amax loads at my oCW optimum of 40.9gr N135, but set to 2.850 (2.220" on the ogive). This is the most I can do while still being able to use the mag and it puts me at 0.035" off the lands.

Using the OAL gauge is a nice way to measure...

So now, I just have to find a day when I can go to try them out.

[surveyor]

James,
If you plan to use it to measure erosion of the throat, keep the bullet you originially used to measure with.

I need to do it again using berger 75 gr, as well as hornady 60, 50, and sierra 50,55,53, among other 6 mm& 30 cal..

It is good to know how to get repeatable measurements transfered to the dies

[Pond, James Pond]

If you plan to use it to measure erosion of the throat, keep the bullet you originially used to measure with.

As I read the post relating to throat erosion I cast my mind back to that very bullet which I seated in a case this very afternoon! Typical!

Will have to do it again with another and keep that.