Okay, I read the thread on this already, and after some investigation of my equipment, I've found that the bullets are indeed inconsistent. However, I've noticed that my dies (Lee RGB, I know, cheap, but they work for now) have a pretty poor seating plug. I looked and measured the plug, and on my .300 mag dies, the Sierra 165 SPBT bullets contact up near the tip (bad for consistent seating depth) and have an inside diameter of around .260" (thus never hitting near what I thought was the o-give). Are there any easy fixes for this in the way of a seating plug that will seat based on the o-give further back (say with an inside diameter of .300" or so)?
I also spoke with a Sierra tech and he said there is usually very little variation in length anywhere on the front of the bullet EXCEPT on the lead tip itself and said the o-give is from the spot where the bullet reaches bore diameter all the way forward to the end of the jacket. If this is true, then wouldn't machining the seater plug to be straightwalled on the inside (and thus making the very rim the only point of contact with the bullet) result in consistent seating depth? If the machining isn't possible, but this method would work, would I be able to use a piece of aluminum or steel tubing of the right size in place of the seater plug?

Basically...what can I do to get consistent seating depth w/o having to ease each bullet down to the proper depth (which is a PITA) and measure with a comparator? Are there other dies that don't cost an arm and a leg that will be much more consistent?

How much variation are your getting when useing your comparator on the cartridge after seating? Is the seating plug hitting the bullet tip or is the contact down on the jacketed nose area?
If the plug contacts the bullet tip a few minutes with a small drill bit and a dremal tool will deepen the plug enough usually to allow the plug to make contact on the jacketed nose only.

I haven't actually loaded any for the .300 yet, and have yet to actually use the comparator. I have only experimented with the plug and the bullets, and have found that it is hitting on the jacketed area of the nose. The very center of the inside of the plug is drilled out so that I don't believe the actual tip will hit. If it's hitting down on the jacket only, would this result in as consistent (or damn near) base to o-give length as if it were hitting further back on the bullet?

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If it's hitting down on the jacket only, would this result in as consistent (or damn near) base to o-give length as if it were hitting further back on the bullet?

It should be OK as long as you are not seating off the bullet tip. Try a couple and use the comparator, you might be pleasently suprised.