Base to ogive help pls

[barefooter56]

Many thanks...the above makes sense but on one point I want to make sure I clearly understand what you are saying.

I got the CBTO comparator tool. On known good ammo my tool gives about 10 hundredths longer measurement (2.5xx vs 2.6xx on my tool). I think you are saying that is fine as different tools will give different measurements than each other, but as long as it is known on YOUR own tool, you can replicate.

I believe this is bc an ogive is not a specific, universal point on various bullets. i.e. on a .308 bullet it is not as easy as saying it is the point where the radius is .306 in diameter...so each comparator will have its own version of where the ogive is.

Is that accurate?
Thx

The Oregonian,
Pick ONE type of bullet comparator and stick with it ! Do not try to check the accuracy of one comparator with another ! Even from the same manufacturer! Bullets base to ojive measurements can vary a little from bullet to bullet in a box and maybe more between lots. By measuring the base to ogive of each bullet and sorting them into lots it will make life easier to be able to make the adjustments on your seating die ( especially if its a micrometer top ) so you can keep all your rounds at the same seating depth on or off the lands. There may also have to be small adjustments in powder charge due to this so you remain on the same velocity accuracy node also.

 

[Mikecr]

Oregonian, you got it right.
And there is no need to mess with bullet base to ojive measurements, as this means nothing to CBTO (which holds the single biggest affect to accuracy).