Seating bullets again

[cdoc42]

There have been threads in the past about seating depths. After reloading my 6mm PPC tonight I thought I'd share this with those of you who seat bullets by measuring from the tip to the base of the case, i.e., OverAll Length (OAL) compared to measuring from the ogive to the base (I call this OAL-OG).

Here's some interesting differences:

I loaded Hornady V-Max 65gr and Berger bullets 68gr. Berger had a different Ballistic Coefficient listed on each of 3 boxes I had: .276, .280 and .293. All the bullets were seated 0.015" away from the leade so they were all equal in that respect. Here's how they measured up:

Hornady OAL= 2.064" OAL-OG = 1.621"

Berger BC .276 OAL= 2.129" Oal-OG =1.639"

Berger BC .280 OAL= 2.089" OAL-OG = 1.639"

Berger BC .293 OAL= 2.134" OAL-OG - 1.639"

Note how wide the variation is if you just measure OAL. If you used the Hornady as your standard and measured it 2.064" then seated Bergers the same OAL, they would be further away from the leade than 0.015" and that could explain why accuracy would suffer in your particular rifle. If you happened to use a Berger and seated it 2.134", then seated the Hornady the same way, the Hornady would be 0.007" closer to the leade while the Berger would be 0.015". Measuring the OAL-OG makes more sense, doesn't it?

[Win_94]

they would be further away from the leade than 0.015" and that could explain why accuracy would suffer in your particular rifle

"Could" is the key word in your theory. Because, you don't know if those bullets work better further.
That is why one develops a load for one particular configuration of components. When any component changes, (especially a bullet, (especially a bullet of differing weights and design,)) one develops a separate load that works well for that component configuration.

(edit)Although it does make sense measuring it that way, because not all bullets of specific types are uniform. So when you measure down the road for a new batch, your measurement could be different by maybe .03" or more.(/edit)

[wncchester]

"(I call this OAL-OG)."

I call it OGL for simplicity.

[Brian Pfleuger]

Of course, getting consistency in that regard also requires a seating plug that actually touches at/near the ogive. Measuring OAL from the ogive and trying to seat from at/near the tip can be an exercise in futility.