Jcinnb
Member
This is old hat to a bunch of you, but some of the newer folks might learn something. I recently started reloading 8mm Mauser. To date I had messed with mostly 25-06 and a little 54r.
For the first time, I loaded two vastly different bullets. The picture shows that the length where the bullets rests against the lands is more relevant, significantly, than overall length.
As is plain to see, the overall length of the two 8 mm's vary greatly, even though they touch the lands at or near the same diameter. The bullet on the left is a Nosler 180 grain and that on the right is a Hornady 170 grain.
I use the Sinclair Intl tool to determing distances and lengths.
I teach math so please forgive the variables.
First, I measure to the rear of bullet, with the pointy end touching the lands. call this a.
Next, I measure to the rear of the cartridge base with the cartridge in the chamber (I guess). Call this b.
Subtracting b from a, gives the distance from the base of the cartridge to the base of the bullet, when the bullet has engaged the lands. Call that measurement, c.
Finally, I add the length of the bullet, d, to c, to get the overall length with the bullet engaging the lands. call that e
To summarize, I get length of the base of cartridge to base of bullet, and add to it, the the length of the bullet, from its base to its tip.
I have been backing off between .005 and .010, but for these guys, I backed off .020.
After I have fired some rounds down range, I will probably move closer to the lands and see how we do.
Anyway, hope this helps someone better understand the critical roll the lands play in determining bullet overall length.
For the first time, I loaded two vastly different bullets. The picture shows that the length where the bullets rests against the lands is more relevant, significantly, than overall length.
As is plain to see, the overall length of the two 8 mm's vary greatly, even though they touch the lands at or near the same diameter. The bullet on the left is a Nosler 180 grain and that on the right is a Hornady 170 grain.
I use the Sinclair Intl tool to determing distances and lengths.
I teach math so please forgive the variables.
First, I measure to the rear of bullet, with the pointy end touching the lands. call this a.
Next, I measure to the rear of the cartridge base with the cartridge in the chamber (I guess). Call this b.
Subtracting b from a, gives the distance from the base of the cartridge to the base of the bullet, when the bullet has engaged the lands. Call that measurement, c.
Finally, I add the length of the bullet, d, to c, to get the overall length with the bullet engaging the lands. call that e
To summarize, I get length of the base of cartridge to base of bullet, and add to it, the the length of the bullet, from its base to its tip.
I have been backing off between .005 and .010, but for these guys, I backed off .020.
After I have fired some rounds down range, I will probably move closer to the lands and see how we do.
Anyway, hope this helps someone better understand the critical roll the lands play in determining bullet overall length.
