quote:

Originally posted by Hot Core:

quote:

Originally posted by DaMan:
...once you establish the caliper measurement of bullet bearing surface to lands that your rifle likes, it will remain the same measurment for all bullet weights and shapes IN THAT RIFLE.

I'm real glad it works that way for you, but I've never seen it happen.

The "Harmonic" is different for each Bullet Weight and for each different Bullet Manufacturer in my rifles.

Plus there is the Changing Throat(Distance to the Lead) which tends to change the Harmonic as well. It typically moves enough to see a difference in Length for 100-shots on the Barrels I've had.

Amazing how we all see different things.

100 Shots, what are you shooting a 50 BMG necked down to 30 caliber?

Nah,

HC's barrels are made of aluminum

quote:

Originally posted by jwp475:
100 Shots, what are you shooting a 50 BMG necked down to 30 caliber?

I was thinking the old .22/50BMG...... but I didn't want to get snarky!

thats funny stuff there DaMan

How do you know .010 off the lands?
Butch

quote:

How do you know .010 off the lands?
Butch

Are you asking how to measure the distance from the ogive to the lands?

That depends on how your reamer is ground. Say it matches your bullet, how do you know that it is .010 from touching.
Butch

Sure Butch, nothing special, I just use one of these:

http://www.midwayusa.com/viewp...productnumber=570611

I'm too lazy to do all the bullet painting with a marker.

Is that a Stoney Point type thing?
Butch

quote:

Originally posted by butchlambert:
Is that a Stoney Point type thing?
Butch

That's the one.

I suppose we should more properly say distance from the ogive ( as measured by the appropriate gauge ) to the engagement point in the throat with the rifling.

I appreciate that there may be some discussion as to what exactly the measurement of "the ogive" should be and it depending on the bore and groove diameter of the barrel but in practice the data is for a particular rifle only anyway and they are useful datum points.

It's most useful if used in conjunction with a seating die where the seating plug that is machined to the same ID as the stoney point insert you are using.

This together with using only the same, scrupulously clean, shellholder cracked the consistent cartridge length problem for me.

So you supply Hornady with a fireformed case so they can make you a somewhat accurate startung place?
Butch

quote:

Originally posted by butchlambert:
So you supply Hornady with a fireformed case so they can make you a somewhat accurate startung place?
Butch

Well I supply Aftab at reloading solutions with a fired case that he drills out and taps for me.

With the case that you can buy even if the fit is not perfect, you can take a number of measurements and come up with a good diea of where you are.

It's either this or the cleaning rod method and going on OAL. This approach is at the mercy of the bullet tip uniformity however.

The cleaning rod with rod stops works exactly the same, same readings tested side by side.

As long as we are concerned with precision seating depth, I will picture my method. I have a "gizzy". Have your gunsmith run the same chambering reamer into a barrel cutoff. It needs to be from the shoulder to the beginning of the rifling. Take a fireformed unsized piece of brass with the primer removed. Stick it into the "gizzy" and take a measurement. Seat a bullet long into the same piece of brass and you can measure the amount the bullet is into the lands.I use my custom micrometer seater to move the bullet back until I get the desired measurement.



I seated the bullet real long to help the illustration. I make my seater with my chambering reamer and have a floating pin that is taper bored to bear on the ogive. I have a Mitutoyo micrometer head mounted to the top of the die.
I do understand that throats erode and after several rounds I have to chase or find the new seating depth. My comp barrels that are not Melonite QPQ are set back after about 400 rounds and used to make dies after 1000-1500 rounds. This is a 6PPC. I also do this on my 30BR. It don't make enough difference to do it on my hunting rifles. I have a self imposed limit of 400yds for deer sized game. I won't get into an argument about that, just my personal deal.
Butch

I see how that works when your barrel is brand new, but I'm really having a tough time understanding it's usefulness after that.

With the cleaning rod or Stoney Point tool, you take the measurement and set up the die with the same bullet. I then seat that very bullet first to the MOAL for the chamber. I then take a MCOAL measurement off of the ogive of that round with my comparator and write it down. All testing can be taken off of that measurement.