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Discussion Starter · #1 ·
So, prior to deciding to get a 6.8 rifle when I looked at exterior ballistics it seemed to me that 6.8 was splitting the difference right down the middle in regards to .308 and 5.56 in terms of muzzle energy. Naturally I assumed then that with the fatter cases the powder charges would be in the mid-30s seeing as many 5.56 loads are in the 25-26 range and .308 in the low-mid 40s.

Well, I've been shocked by all these hotter loads running just 29.5-31 grains of powder. I know the burn rates are a bit faster compared to 5.56 due to the bore/case diameter ratio but this is way beyond what I expected.

Maybe I suck at physics but I'm having a hard time understanding how seemingly small increases in charge weight results in overwhelmingly stronger terminal ballistics for the 6.8.
 

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It sure is a sweet spot. A little more powder, with a little faster burn rate, than 223, and bullets a little lighter than a .308. You have your cake now get ready to eat. :a21:

So, I lack a more refined answer than, "It just does".
 

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It sure is a sweet spot. A little more powder, with a little faster burn rate, than 223, and bullets a little lighter than a .308. You have your cake now get ready to eat. :a21:

So, I lack a more refined answer than, "It just does".
sounds like physics to me
 

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So, prior to deciding to get a 6.8 rifle when I looked at exterior ballistics it seemed to me that 6.8 was splitting the difference right down the middle in regards to .308 and 5.56 in terms of muzzle energy. Naturally I assumed then that with the fatter cases the powder charges would be in the mid-30s seeing as many 5.56 loads are in the 25-26 range and .308 in the low-mid 40s.

Well, I've been shocked by all these hotter loads running just 29.5-31 grains of powder. I know the burn rates are a bit faster compared to 5.56 due to the bore/case diameter ratio but this is way beyond what I expected.

Maybe I suck at physics but I'm having a hard time understanding how seemingly small increases in charge weight results in overwhelmingly stronger terminal ballistics for the 6.8.
Faster burn rate is the biggest +. Case cap is the same as the Grendel but the faster powders produce quiet a bit more vel.
 

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It sure is a sweet spot. A little more powder, with a little faster burn rate, than 223, and bullets a little lighter than a .308. You have your cake now get ready to eat. :a21:

So, I lack a more refined answer than, "It just does".
"How exactly does the posi-trac rear end work on a Plymouth work? It just does!"
 

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Discussion Starter · #6 ·
Faster burn rate is the biggest +. Case cap is the same as the Grendel but the faster powders produce quiet a bit more vel.
Going to have to start playing around in Quickload, I hope it is up to date on 6.8. Depending on what it looks like I'll stock up on either Re7, Norma 200 (if they are indeed the same I will stock up on the Norma), or aa2200. I'll just be loading 95 grain TTSX.
 

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So, prior to deciding to get a 6.8 rifle when I looked at exterior ballistics it seemed to me that 6.8 was splitting the difference right down the middle in regards to .308 and 5.56 in terms of muzzle energy. Naturally I assumed then that with the fatter cases the powder charges would be in the mid-30s seeing as many 5.56 loads are in the 25-26 range and .308 in the low-mid 40s.

Well, I've been shocked by all these hotter loads running just 29.5-31 grains of powder. I know the burn rates are a bit faster compared to 5.56 due to the bore/case diameter ratio but this is way beyond what I expected.

Maybe I suck at physics but I'm having a hard time understanding how seemingly small increases in charge weight results in overwhelmingly stronger terminal ballistics for the 6.8.
It is a combination of Black Magic and Rocket Science but even the rocket scientists do not understand it.
 

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Going to have to start playing around in Quickload, I hope it is up to date on 6.8. Depending on what it looks like I'll stock up on either Re7, Norma 200 (if they are indeed the same I will stock up on the Norma), or aa2200. I'll just be loading 95 grain TTSX.
Quickload is not that accurate in predicting 6.8 load velocity/pressure. It seems QL has as much difficulty quantifying the "mystery of low charge weight producing high performance" in the 6.8 as we all do.:a21:

For 95 gr. TTSX, I like 30 gr. of A2200 with COL of 2.290" (published max. is 30.2 with COL of 2.260"). That load produces over 2,800 fps from my Mini-14's 18.5" barrel and the 16" barrel ARP barrel and about 2,950 fps from my 20" bolt gun. And, it's very accurate in all three rifles.
 

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FM..........
 

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Going to have to start playing around in Quickload, I hope it is up to date on 6.8. Depending on what it looks like I'll stock up on either Re7, Norma 200 (if they are indeed the same I will stock up on the Norma), or aa2200. I'll just be loading 95 grain TTSX.
Why expend a lot of effort reinventing the wheel? There is tons of data available for every suitable powder in the 6.8. If I could only use one, it would be 2200. It works from 90 gr. up to 120 gr., is very predictable, and provides superb accuracy in most rifles. 28.5 gr. with 110 gr., 30.5 with 90 gr., everything else is just a variation on those two.
 

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Why expend a lot of effort reinventing the wheel? There is tons of data available for every suitable powder in the 6.8. If I could only use one, it would be 2200. It works from 90 gr. up to 120 gr., is very predictable, and provides superb accuracy in most rifles. 28.5 gr. with 110 gr., 30.5 with 90 gr., everything else is just a variation on those two.
Absoluetly +1 X 10. 2200 is my go to powder. Deadly accurate with TNT 90's and 30.5 and mag primers. Excellent with 110 ABOND and 110 Sierra. In all loads I've found better accuracy with mag primers and 2200.
 

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Discussion Starter · #13 · (Edited)
Why expend a lot of effort reinventing the wheel? There is tons of data available for every suitable powder in the 6.8. If I could only use one, it would be 2200. It works from 90 gr. up to 120 gr., is very predictable, and provides superb accuracy in most rifles. 28.5 gr. with 110 gr., 30.5 with 90 gr., everything else is just a variation on those two.
I found a post of Constructor's on another site:

120SST
33gr Lever-2497fps and 49201psi-compressed max fill
31gr 8208-2558fps and 56923psi-compressed max fill
31gr H335-2542fps and 57091psi
30gr Xterm-2506fps and 57279psi
33gr 2520-2584fps and 54789psi-compressed max fill
28.2gr 2200-2609 and 57312psi---see "testing primers" note below
29gr 2200-2652fps and 59778psi
29gr 1200R-2597fps and 59703psi
27.5gr Norma200-2536 and 58060psi
29.5 N530-2612fps and 57kpsi
28.2gr 10X-2561 and 55900psi

95gr TTSX-Top performing powders, any slower burning powders will produce less velocity
29.5gr 2200-2801fps-54260psi
30.5gr 2200-2889fps-57928psi
30.5gr RE7-2905fps-58100psi
29gr Norma 200-2819fps-55052psi
29.gr Norma 200-2862fps-57954psi
30gr N530-2709fps-50974psi
27.8gr 1680-2854-58163psi

18" barrel 2.3 COAL
Something wrong with that 2nd Norma 200 charge weight, a missing decimal. Its looking like RE7/Norma 200 could be better for 95gr or at least equal.

In other powders that are rebranded (Norma 203B and MRP) I found the Norma brand to be more consistent than the Alliant (RL-15 and 22).
 

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Discussion Starter · #14 ·
Well, I fired up QL but I'm way back on 3.6 and foudn out they make you pay for updates so have 3.9 coming.

Many bullets aren't in it including the 95 ttsx but it seems like for the ones I'm checking out the data jives with what is here. It also lets me compare powders and looks like RE-7 and Norma 200 are very different. Comparing those to AA220 Norma 200 is the clear winner for velocity in any bullet I've checked so far.
 

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Discussion Starter · #15 ·
After updating quickload now it has the 95 grain ttsx but sadly it gives the stupid high pressure numbers others have noted.

Rats.
 

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After updating quickload now it has the 95 grain ttsx but sadly it gives the stupid high pressure numbers others have noted.

Rats.
This is exactly why I have never gotten too excited about QuickLoad. Actual real world load testing is much more accurate in my opinion. Too many people don't understand that QL is only meant to get you in the ballpark, not put you on 3rd base with the winning run and no outs.
 

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Discussion Starter · #17 ·
This is exactly why I have never gotten too excited about QuickLoad. Actual real world load testing is much more accurate in my opinion. Too many people don't understand that QL is only meant to get you in the ballpark, not put you on 3rd base with the winning run and no outs.
In the past I've found it to be scary accurate for .308 and .30-06.

No joy on straight wall cartridges like .44 Mag and .45-70 though.
 
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