Gentlemen, here?s a set of ?equivalent? lengths for Rainier Plated HP.

115 gr HP, 0.515

124 gr HP, 0.547

Rationale and methodology: The Rainier HP bullets have concave bottoms. Physical length isn?t meaningful because there is a concave volume down there. For the purpose of figuring out bullet seating depth, the length of an equivalent flat bottom bullet is good enough to calculate the remaining case volume.

You can check my math.

1. Average of 5 bullets is 115.0 gr. The length is 0.525, BUT the bottom is concave.

2. I sanded off the concave bottom of a 115 gr Rainier HP. The bottom is now flat. The bullet weigh in at 111.7 gr and 0.503 long.

3. That means the removed lead from the concave bottom is 3.3 gr.

4. Question: We want to add that same volume of lead back to the bottom of the bullet in the form of a 0.355 diameter disk. What would that length be?

5. 1 gm = 15.4 gr. So 3.3 grain = 0.214 gm

6. Lead has a density of 11.34 gm/cm3. So 0.214 gm =>0.0189 cm3.

7. 1 in3 =16.39 cm3. So 0.0189 cm3 => 0.001153 in3

8. The area of a 0.355 disk (added to the bottom of the bullet) is 0.0989 in2. 0.001153 in3 would fit in 0.0117 in length.

9. Add that 0.0117 to the 0.503 from the shortened 111.7 gr gives 0.5147. round off to 0.515.

Do the same thing for the 124 gr bullet. You need to shave off 12.3 grain. That extra length comes out to 0.0436. Add that to 0.503, we get 0.547.