Theory

[rero360]

I may be wrong here, hence the label of Theory, let me know what you think:

I'm loading up a .308win load, BH brass, 175gr SMK with fed primers and Varget powder.

I got thinking about COAL and variations in the tip of the bullet. I took a sample of the 500 odd bullets I have on hand and found that they varied in length by 0.01, not a whole lot. Taking the longest bullet in my sample, shouldn't matter as the diverging parts are just in the tip and loaded up a dummy round to find the COAL to just touching the lands, came out to be 2.805

Now given the fact that my seating die doesn't index off of the tip, rather a bit further down on the bullet as proven by a ring indented into the bullet, I can then go off the assumption that every round loaded with the die at that setting would be to the lands with a COAL varying by 0.01

Also, by knowing the length of the individual bullet in relationship to the test round, I can make reasonable adjustments to my die to dial in for that sweet spot in load development once I find a good powder charge and be sure of where I stand in relationship to the jump to the lands.

Am I right in this train of thinking? partially? completely out in left field?

 

[Victor N TN]

Re: Theory

SMKs may vary as much as .020" OAL or Base to Ogive in a single box.

If you alter the nose punch profile to touch farther down nearer the actual ogive you will get more consistant lengths when measuring from base to ogive.

Some die makers will offer this for a minimum charge if you send them the top punch and 3 bullets of the type you want to shoot.

 

[ChadTRG42]

Re: Theory

I think I know what your asking. Most HP bullets will vary a bit just by the tip. If you can take a measurement of the ogive and seat to this, it will be more consistant. The die should seat the bullet to the same ogive (given the same neck tension from round to round), and the COAL will vary by the difference in the tips of the bullet. Does that answer your question?

 

[bohem]

Re: Theory

Interesting idea, as I'm understanding his question I think Chad nailed it. I have nothing to offer, just reading. Thanks