Mitdr774 Wrote:One can shoot 100gr 6mm bullets at 2700 FPS and one can shoot 100gr 6.5mm bullets at 2700 FPS. I would think the 6mm would be better suited for longer range applications.

Mitdr774 Wrote:Weight for weight the smaller diameter should have a higher SD and potential for penetration. I was just over simplifying with my statement. I will probably add a 6mm ARC for the same reason I picked up a 6.5G. The Grendel is a more cost effective 6.5mm alternative to my 6.5x55 and the ARC would be a more cost effective alternative to my .243. The ARC should be easier on the barrel as well. The .243 sure does get hot quick.

HuntTXhogs Wrote:The limited offerings in 6.5 and 277 that fit within Grendel and 6.8’s grain weight are short and stubby whereas the 6mm 90 grain are longer and therefore have a higher sectional density....

Mitdr774 Wrote:SD might be a function of weight and diameter, but as you go up in diameter you also loose length for the same given weight. While length may not be part of the math equation to figure out SD, it is something that is involved in the final product. Given the same construction and design, a long "heavy" 6mm will have a better SD than a short "lightweight" 6.5mm if they are both the same weight. This long and heavy for caliber should also result in a better BC.

Nosler Partition 100gr (all numbers sourced from Midway)

.243" SD of .242, 1.065" length, G1 BC .384
.257" SD of .216, 1.035" length, G1 BC .377
.264" SD of .205, 0.962" length, G1 BC .326

HuntTXhogs Wrote:I didn’t mean ballistic coefficient - I’m talking about sectional density BUT I will grant that I don’t fully understand the calculations to establish what SD is for a given bullet. Even after reading the Chuck Hawks page I couldn’t get the formula to spit out the SD for a known weight and caliber and the charts are confusing as heck...

Here is what SD means to me :

Note- I’m probably wrong from a technical aspect but given my approximations I’m thinking I’m more right than wrong in realistic application (hunting only).

This article is where I derived that bullet length has an impact on SD : https://ronspomeroutdoors.com/blog/bullet-sectional-density-matters/

Again maybe I’m reading it wrong but there are a few statement in the article that clearly lead a lay man to believe bullet length is a contributing factor to SD.

Now, in my head, I rely on some past experiences and posted data (Midway will work for this example) to derive a understanding of what I’m shooting into game.

When I pick up a 223 I ordinarily choose a 62 grain bullet / when I pickup a .243 it shoots a 95 grain / 308 is usually 165 grain / 458 will dispense a 250 grain and so on.

As I look at the available ammunition and bullet choices the number of options are generally clumped in the bullet weights above - these represent the grain weights with the widest hunting utility in the field (no speciality utilization). AND I don’t need to run and grab a calculator but I’d bet a steak dinner that the SD is higher as you work from . 22 to .458....

MY POINT: for the 6-ARC discussion and 90 grain bullets available in other calibers that match the AR-15 profile (Gren and 6.8) is that hunters can only choose what the market bears (ammo makers have focused on other weights for 6.5 and .277) and so in this case the SD charts are thrown upside down because the 6mm 90 grain has a higher SD grain for grain - which isn’t the norm when typically “stepping up” in calibers.

Hopefully this explains my position and understanding a bit more -

Oh and don’t get me wrong, if you give me a 308 and I get to choose the ammo to hunt hogs from 3 grain weights (110 grs / 165 grs / 220 grs) I’m going to choose the 165 grain all day long (given the same bullet construction/properties). That choice isn’t based on SD alone rather there is recoil, trajectory, and penetration all factoring into that decision.

But I’ve learned to never discount a few special grain weights and caliber combos that buck the math and just work and work well despite the ordinary school of thought - the 90 grain Speer TNT on hogs is one of those “Huh?” choices for hogs.

And therefore what if I could supercharge that 90 grain TNT - I.e. 6-ARC bonded bullet (YES theoretically speaking)

Harpoon1 Wrote:Not sure what your trying to illustrate with those “numbers sourced from Midway”. No one said higher SD bullets can’t be longer, I’m saying length is not the reason why they have a higher SD, that’s all.

How do you reconcile this? Compare two 90 grn 6mm bullets. One solid lead, the other solid copper. I think most would agree the solid copper bullet would then have to be much longer because, copper is less dense than lead. Right? Yet both would still have the exact same SD. And the solid copper bullet, all things being equal, could also have a much higher BC, yet the same SD.

Silverjay Wrote:Picked up a box of 95 grain Berger classic hunters. Quickload predicts 2,743 for CFE223 and 2,720 for Hogdon LVR. Any other powders of interest? 8208, TAC, and 3031 all show velocities in the 26’s. I plan to run ladders tomorrow.

kmon Wrote:Not sure if this one is on the Midsouth site

[video=youtube;jdiFmouGXWc]https://www.youtube.com/watch?time_continue=2&v=jdiFmouGXWc&feature=emb_logo[/video]

Silverjay Wrote:Data from 95 grain Berger classic hunter and CFE223. Work up slow if you base off of this.

28.0 2,624
29.0 2,688
29.4 2,722
29.6 2,773
29.8 2,795
30.0 2,808
30.2 2,811
30.4 2,838
30.6 2,886
30.8 2,881
31.0 2,917 Quickload predicts pressure at 52,500
31.2 2,901
31.4 2,929

Ejection pattern shifted from 4:00 to 3:00 at 31.0 grains and higher. The case and volume data I used for 108 ELD’s gave almost exact velocities, same cartridge data for this load predicted 2,720 at 31.0 grains and actual was 200 FPS faster. No pressure signs on the brass. Primers are S&B ST and still have nice rounded shoulders. No ejector marks.

Across a 10 round set of 31.0 grains the average velocity was 2895 with an SD of 6. This is at 93 degrees F ambient.