06-25-2020, 03:09 PM
From Harpoon:
"My only point was, you cant assume because a bullet is longer, it will have a higher SD or have more penetration. Thats all." Technically correct, but practically IMO not very useful to me as a shooter as I will go into below.
The formula for sectional density (SD) is:
SD= M/(D^2), where M is the mass of the bullet (in lbs, or grs/7000); and D is the diameter of the bullet (inches).
SD = [Mass (in grains) / 7000] / (bullet-diameter in inches)².
So technically speaking the "Length" of the bullet is not required. BUT, practically speaking, (and Spomer indicates this as well), for given bullet constructions, more length in a caliber means higher SD due to higher mass.... and as well, smaller diameter for same-style bullets of EQUAL mass will also yield higher SD. It might be true concerning the comment above about all-copper vs all-lead pills at equal mass, but there are no all-lead bullets we shoot, and few all-copper. So that is not a strong distinction, nor do many guys consider that when choosing a caliber or bullet, (this is my guess).
The material variations of copper jacket/composition/thickness for different mfrs, or lead alloy composition; are minor and beyond our ability to control, so the boundary condition of "similar bullet construction" usually applies. So practically speaking, as DNS illustrates, you pick the bullet for the purpose b/c you have already decided on the gun (ie, caliber)...
If we want to compare over different calibers, then constant mass in varying diameters (bullet construction being mostly constant), means smaller diameter will necessarily have a longer body, since the SD comes from the Mass/D^2 figure, SD will increase for the smaller diameter-caliber over the larger caliber, under these bounding conditions. As shooters we typically have a finite list of bullets to choose from, so SD comes from either a longer/heavier bullet at one caliber or a smaller caliber bullet of equal (or sometimes even smaller) mass. It just depends on how the formula results come out for those two bullets.
For the 6Arc I would expect, for similar mass values to a 6.5 bullet, slightly better down-range performance within limits. But for the grendel, you have the ability of using heavier bullets, which usually means better KE for many hunting applications.
In my case, hunting under ~300 yds either caliber will work for my purpose so I plan on having both.
"My only point was, you cant assume because a bullet is longer, it will have a higher SD or have more penetration. Thats all." Technically correct, but practically IMO not very useful to me as a shooter as I will go into below.
The formula for sectional density (SD) is:
SD= M/(D^2), where M is the mass of the bullet (in lbs, or grs/7000); and D is the diameter of the bullet (inches).
SD = [Mass (in grains) / 7000] / (bullet-diameter in inches)².
So technically speaking the "Length" of the bullet is not required. BUT, practically speaking, (and Spomer indicates this as well), for given bullet constructions, more length in a caliber means higher SD due to higher mass.... and as well, smaller diameter for same-style bullets of EQUAL mass will also yield higher SD. It might be true concerning the comment above about all-copper vs all-lead pills at equal mass, but there are no all-lead bullets we shoot, and few all-copper. So that is not a strong distinction, nor do many guys consider that when choosing a caliber or bullet, (this is my guess).
The material variations of copper jacket/composition/thickness for different mfrs, or lead alloy composition; are minor and beyond our ability to control, so the boundary condition of "similar bullet construction" usually applies. So practically speaking, as DNS illustrates, you pick the bullet for the purpose b/c you have already decided on the gun (ie, caliber)...
If we want to compare over different calibers, then constant mass in varying diameters (bullet construction being mostly constant), means smaller diameter will necessarily have a longer body, since the SD comes from the Mass/D^2 figure, SD will increase for the smaller diameter-caliber over the larger caliber, under these bounding conditions. As shooters we typically have a finite list of bullets to choose from, so SD comes from either a longer/heavier bullet at one caliber or a smaller caliber bullet of equal (or sometimes even smaller) mass. It just depends on how the formula results come out for those two bullets.
For the 6Arc I would expect, for similar mass values to a 6.5 bullet, slightly better down-range performance within limits. But for the grendel, you have the ability of using heavier bullets, which usually means better KE for many hunting applications.
In my case, hunting under ~300 yds either caliber will work for my purpose so I plan on having both.
"Down the floor, out the door, Go Brandon Go!!!!!"