CBTO and Lands and different Bullets

[CanMike]

I may be overthinking this.

So if I use one bullet let’s say the 140 ElDM to find the lands and get a CBTO measurement there.

Now if I want to seat 0.020 off that point I just adjust down my seating die etc. pretty simple.

Now if I have second bullet let’s say the 153 ATIP can I use the above CBTO of lands and adjust accordingly.

My understanding is that the OGIVE is the point the bullet engages the rifling. So that theoretically should be same across all brands of bullets? Obviously at a different point on each type of bullet but CBTO to lands should be same across all bullets?

Thanks
Mike

 

[John Glidewell]

No. Every bullet will be different and some will be different lot to lot.

 

[Hickswr]

Bearing surface lengths of different bullets varies greatly.

Just picture a 95gr v-max bullet vs a 153gr a-tip. They will start to engage the rifling at vastly different CBTO lengths.

 

[Im2bent]

I was under the impression that the contact point/diameter is what it is and that length will be the same, that being said different bullet different seating depth to get that dimension

 

[John Glidewell]

Different Ogives engage in different places. Secant, Tangent, Hybrid and now the newer long range hybrid designs. They will all be different CBTO.