Stumped .......

[mkk]

Used the Hornady OAL gauge to check the position of the lands to work on seating depth.

First bullet I used was a Hornady 178g A-Max and got a reading of 2.240 using the comparator.

2nd bullet was a 180g Hornady Interlock and got the same reading of 2.240

Now I try the Nosler 150g Accubond and get a reading of 1.900

I have spent the better part of the afternoon measuring and re-measuring and have come up with the same results. What am I missing

 

[FearNoWind]

Likely dealing with a difference in bullet profile. Check the technical data on the bullets and see how they compare with respect to profiles (secant, tangent, scenar)

 

[mkk]

The measurement comes from the ogive so it should be the same no matter what the bullet shape is.................right?

 

[FearNoWind]

The measurement comes from the ogive so it should be the same no matter what the bullet shape is.................right?

Yes, I agree with that. However the Hornady OAL gauge (not a laboratory instrument) has an internal profile that doesn't match every bullet precisely and I've found that bullet profile differences will produce different results using that device. That's not to say your issue is rooted in instrument's accuracy. It may be something else. I just wanted to provide you with a possibility that you might want to explore in find a solution to your problem.

 

[mkk]

That makes sense. Ill try some different brands and styles of bullets and see how the measurment changes

 

[lamiglas]

after using the comparator and measureing to the ogive, are you saying that the tip to tip measurements are different, or the actual head to ogive measurment is different?

 

[climb-101]

the base to the ogive should always be the same (providing you are measuring to the lands) since that's measurement can't change because that's the bolt to the lands. the OAL of the bullet can change though because the different profiles of the bullets

 

[mkk]

the base to the ogive should always be the same (providing you are measuring to the lands) since that's measurement can't change because that's the bolt to the lands. the OAL of the bullet can change though because the different profiles of the bullets

That is what has me stumped, I am getting 2 different measurements using different bullets.

2.240 on the Hornadys
2.190 on the Nosler

I jammed both bullets into the lands and tightened the set screw on the gauge. I know both were seated into the lands because I had to tap the bullet out with a cleaning rod.

 

[mkk]

after using the comparator and measureing to the ogive, are you saying that the tip to tip measurements are different, or the actual head to ogive measurment is different?

Head (base) to ogive is different

 

[climb-101]

I could see being off .001-.002 but .050 isn't even in the ball park. have you measured the diamiter of the bullets? maybe one is out of spec, another thing to try is clean the barrel then remeasure. I once had some inconstant readings and that we t away once I cleaned the barrel good. also it help to use a case that has been fired from the gun and modified for the compariter

 

[Gene]

Take a caliper OAL tool reading from the same bullet 5 times and average them. That figure will get you close. Next, seat that bullet in a sized, empty unprimed case to the average figure you found in the first 5 measurements. Again use the caliper. Write it down.

Now neck size the case again and seat same bullet to the average figure. Once seated tight in the case mouth, rub it with 0000 steel wool. Put this dummy round in chamber; remove it carefully, and look closely at the bullet and find marks where the lands scraped it. (View it with a jewelers loop or magnifier.) If no such marks found, you need to seat the bullet out a little further and try again. If the marks are heavy, turn your seater die down slightly.

Countinue doing this until you can barely see the land rub marks. This will be your touch point where the bullet is just kissed lightly. Write it down. Using that number you will be able to jump or jam those same bullets and find the most accurate seating depth.

 

[lamiglas]

Maybe try pushing the rod forward lightly just until it stops, making sure that you aren't jamming it into the lands more on one bullet than the the other due to bullet shape? Like mentioned before, take 5 measurments to make sure you are being consistent. Also, especially if you are jamming them into the lands, you will need to switch bullets after a few measurements. As your jacket wears, so will the measurement. Just some thoughts. Good luck man.

 

[Corey Schwanz]

A measurement to the lands with a comparator can and will be different with various bullets. Different bullets have different profiles and will need to be seated further or shorter than other to actually touch the lands. The lands don't move obviously, but bullets with a shorter bearing surface will need to be seated at a different depth to touch than those that have a longer bearing surface. Pick one comparator and stick with it. Its no surprise 2 different brands of bullets have 2 different depth measurements when touching the lands. If you get a 3rd bullet, I'd bet you'd get a 3rd different reading.

 

[Canadian Bushman]

That is what has me stumped, I am getting 2 different measurements using different bullets.

2.240 on the Hornadys
2.190 on the Nosler

I jammed both bullets into the lands and tightened the set screw on the gauge. I know both were seated into the lands because I had to tap the bullet out with a cleaning rod.

Depending on the ogive radius and lead angles some bullets will jam significantly further into the lands than others.

I personally measure with a light touch to find where the lands start. Most call the condition youre checking "full jam", which is the maximun you can jam a bullet into the lands without drastically increasing force required to close the bolt.