Da..it, Don't shortchange me! 6.5 Grendel vs. 6.8 SPC
- Thread starter autobahndriver
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Zak Smith
Member
Very roughly, the 6.5 Grendel shoots a narrower bullet of similar weight to what the 6.8SPC shoots. The narrower profile of the 6.5 Grendel bullet means the ballistic coefficient (BC), a measure of how easily it slips through the air, is higher. The 6.5 Grendel will lose velocity at a slower rate than the 6.8SPC, and consequently, the 6.5 Grendel will have less drop at the same distance vs. 6.8SPC. The difference is academic within 300 meters, but starts to add up at 500 meters and beyond.
As an analogy, you could think of 6.5 Grendel to 6.8SPC kind of like miniature versions of 7Mag vs. .30-06. With a 150gr bullet, both are right around 3000fps, but the 7Mag's bullet is slimmer and it retains velocity better and has less drop.
I think we're still waiting for good terminal ballistics data on te 6.5 Grendel, but some with experience in FBI-protocol gel tests believe the 6.5 will have a longer "neck" (before violent expansion/tumbling) in the wound profile.
-z
As an analogy, you could think of 6.5 Grendel to 6.8SPC kind of like miniature versions of 7Mag vs. .30-06. With a 150gr bullet, both are right around 3000fps, but the 7Mag's bullet is slimmer and it retains velocity better and has less drop.
I think we're still waiting for good terminal ballistics data on te 6.5 Grendel, but some with experience in FBI-protocol gel tests believe the 6.5 will have a longer "neck" (before violent expansion/tumbling) in the wound profile.
-z
autobahndriver
Member
From what I've read the 6.8 SPC is shooting at 1.0 MOA at 300 meters - the cutoff threshold.
Doesn't matter anymore...the SOCOM requirement is now a light version that must be in 5.56 and a heavy version that is in 7.62 and can take other calibers for long range shooting.
From Remington press release:
"...The 6.8mm Remington SPC, (Special Purpose Cartridge) will be offered in three versions for 2004, including Remington's new Premier® Match, line of ammunition. The 115 grain MatchKing® BTHP bullet will deliver a muzzle velocity of 2800 fps and 2002 ft-lbs of energy while providing low felt recoil and 1 MOA accuracy at 100 yards. The 6.8mm Remington SPC will also be available in both BTHP and Metal-Case 115 grain versions..."
On the recent SOF article extolling the virtues of the 6.8 SPC:
Firing was limited to 25 yards, so no accuracy data was obtained. Johnston expects 1 MOA accuracy, equivalent to a PRI 6.8mm rifle he has fired.
Doesn't matter anymore...the SOCOM requirement is now a light version that must be in 5.56 and a heavy version that is in 7.62 and can take other calibers for long range shooting.
From Remington press release:
"...The 6.8mm Remington SPC, (Special Purpose Cartridge) will be offered in three versions for 2004, including Remington's new Premier® Match, line of ammunition. The 115 grain MatchKing® BTHP bullet will deliver a muzzle velocity of 2800 fps and 2002 ft-lbs of energy while providing low felt recoil and 1 MOA accuracy at 100 yards. The 6.8mm Remington SPC will also be available in both BTHP and Metal-Case 115 grain versions..."
On the recent SOF article extolling the virtues of the 6.8 SPC:
Firing was limited to 25 yards, so no accuracy data was obtained. Johnston expects 1 MOA accuracy, equivalent to a PRI 6.8mm rifle he has fired.
autobahndriver
Member
Quote from Das Pherd: "My head is killing me. After do many searches, all I see is people quoting ballistics etc. I know nothing about ballistics. Can someone do a side by side of these two rounds in laymans terms?"
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Basically the two bullets are almost the same in diameter but the 6.5 is a little longer and heavier bullet.
The complete cartridges weigh the same and have case heads about the same size.
Almost the same bullet right???
Wrong...the higher BC of the longer round makes a big difference.
While both show very little difference in velocity or energy delivered at short ranges (under 300m), the longer 6.5 round keeps more velocity as it travels further.
By keeping more velocity, the 6.5 has more knock down energy at long range.
The 6.5 is not effected as much by wind at long range.
The 6.5 does not drop as far at long range (don't have to adjust scope as much or worry about how the angle of shot will effect your trajectory as much).
I'll try and do some graphics and post sometime to illustrate the differences.
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Basically the two bullets are almost the same in diameter but the 6.5 is a little longer and heavier bullet.
The complete cartridges weigh the same and have case heads about the same size.
Almost the same bullet right???
Wrong...the higher BC of the longer round makes a big difference.
While both show very little difference in velocity or energy delivered at short ranges (under 300m), the longer 6.5 round keeps more velocity as it travels further.
By keeping more velocity, the 6.5 has more knock down energy at long range.
The 6.5 is not effected as much by wind at long range.
The 6.5 does not drop as far at long range (don't have to adjust scope as much or worry about how the angle of shot will effect your trajectory as much).
I'll try and do some graphics and post sometime to illustrate the differences.
Grump
Member
Isn't the 6.8 SPC just a 5.56 necked up to 6.8mm? The Grendel is a larger case diameter, adapted (not adopted) from the 7.62x39. That means more powder, more reserve horsepower.
I'm still not sold on the 144-gr 6.5mms. It's virtually the same amount of metal overall as the M80 ball bullet, and has a much more loopy trajectory. Goes to slow for me. I would *guess* that it would take longer to flip over on the terminal ballistics side of life.
I'm still not sold on the 144-gr 6.5mms. It's virtually the same amount of metal overall as the M80 ball bullet, and has a much more loopy trajectory. Goes to slow for me. I would *guess* that it would take longer to flip over on the terminal ballistics side of life.
Zak Smith
Member
No. It's a shortened .30 Remington case.
-z
autobahndriver
Member
Grump Quote: "I'm still not sold on the 144-gr 6.5mms. It's virtually the same amount of metal overall as the M80 ball bullet, and has a much more loopy trajectory. Goes to slow for me. I would *guess* that it would take longer to flip over on the terminal ballistics side of life."
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What do you think about the 123-gr 6.5?
Saw a recent posting on another unnamed forum (membership rules) showing the 144-gr having a drop of -355.15 at 1000 yds with 100 yd zero.
It shows the 7.62 NATO 175 OTM Sierra at -397.84 at the same dist.
Velocities are 1411 for the Grendel and 1222 for the 7.62 at 1000 yard distance.
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What do you think about the 123-gr 6.5?
Saw a recent posting on another unnamed forum (membership rules) showing the 144-gr having a drop of -355.15 at 1000 yds with 100 yd zero.
It shows the 7.62 NATO 175 OTM Sierra at -397.84 at the same dist.
Velocities are 1411 for the Grendel and 1222 for the 7.62 at 1000 yard distance.
sumpnz
Member
If you look at the ballistics chart, the 144 grain 6.5mm starts to have a significant advantage in drift over the M80 by 400 meters, though the difference in drop is academic until you get out to about 900 meters. In terms of velocity, by a little over 400 meters the Grendel has caught up to the M80, and thereafter is faster. Terminal effects are still a ?.
However, I think the 123 grain 6.5mm is really the better comparison to the M80. The 144 grain 6.5mm is really better compared to the 175 grain Long Range 7.62mm. Because 123 grain Grendel round 24 grains lighter than the M80, it will take a while for the energy to catch up, but the energy really is more of an academic measurment anyway. In that sense, so long as it has the energy to get the job done, it really doesn't matter if something else has more energy. Therefore, in this comparison, drop, drift, and retained velocity matter more. But at any rate, the 123 grain Grendel starts off only 100 fps slower than the M80, and by just 200 meters is already going faster. Somewhere between 500 and 600 meters the 123 grain 6.5 takes over in terms of energy from the M80 and by 600 meters it has a 155 fps advantage. In terms of drop and drift, the 6.5 starts to have a noticable advantage by 700 meters and 400 meters respectivly over the M80.
Just being contrary here, but has anybody though that the "if" of either of these rounds acceptance, might untimately hinge on preformance in the SAW platform? 500-600 yds is the real practical limit of expectations in the M16/AR platform. But if they modify a SAW for either of these rounds and 800+ yards is going to evaluated.
Personally I don't put much hope in acceptance of either round, and when and if they do I certainly hope that it does not skip the testing cycle in the evaluation.
From the very high level, I would lean towards the 6.5 option. But that doesn't mean that a better mousetrap might be the 6.5mm bullet on the SPC case design.
The good news is the bureaucracy is looking at other options, but what the final solution will be once it runs through that cycle, I wouldn't even venture to guess.
Personally I don't put much hope in acceptance of either round, and when and if they do I certainly hope that it does not skip the testing cycle in the evaluation.
From the very high level, I would lean towards the 6.5 option. But that doesn't mean that a better mousetrap might be the 6.5mm bullet on the SPC case design.
The good news is the bureaucracy is looking at other options, but what the final solution will be once it runs through that cycle, I wouldn't even venture to guess.
Grendelizer
Member
Schromf, on May 6, 2004, TX65 posted on THR: "A M249 project is already underway on the 6.5 Grendel."
You wrote: "A better mousetrap might be the 6.5mm bullet on the SPC case design." The 43mm SPC case is a poor fit for an intermediate cartridge in the AR form factor because it limits one to short bullets with their corresponding degradation in trajectory, drift, and penetration. If you want a short bullet in the 6.5 Grendel, you can certainly do so if you choose, but you can also use longer bullets with their corresponding benefits.
John
You wrote: "A better mousetrap might be the 6.5mm bullet on the SPC case design." The 43mm SPC case is a poor fit for an intermediate cartridge in the AR form factor because it limits one to short bullets with their corresponding degradation in trajectory, drift, and penetration. If you want a short bullet in the 6.5 Grendel, you can certainly do so if you choose, but you can also use longer bullets with their corresponding benefits.
John
Tony Williams
Member
If you want to broaden your education a bit
you could try reading up on basic ballistics here: http://www.quarry.nildram.co.uk/ballistics.htm and on assault rifle ammo (including some discussion of 'ideal' types) here: http://www.quarry.nildram.co.uk/Assault.htmTony Williams: Military gun and ammunition website and discussion
forum
Zak Smith
Member
INFO REQUEST
Since you 6.5 Grendel guys are reading this thread, I have a request...
I am looking from some actual first-hand chrono data for 6.5 Grendel fired from an 18" barrel, with the 108 - 123gr bullets. Not what you've heard, not from a 24" barrel.
If you don't have that, data from any barrel from 16-20" would do.
thanks
Zak
Since you 6.5 Grendel guys are reading this thread, I have a request...
I am looking from some actual first-hand chrono data for 6.5 Grendel fired from an 18" barrel, with the 108 - 123gr bullets. Not what you've heard, not from a 24" barrel.
If you don't have that, data from any barrel from 16-20" would do.
thanks
Zak
Grump
Member
Me too!!!
Me Too!!!
Yeah, I want to see our fellow THR dudes' and dudettes' actual chrono data....for BOTH the Grendel and the SPC.
Me Too!!!
Yeah, I want to see our fellow THR dudes' and dudettes' actual chrono data....for BOTH the Grendel and the SPC.
Zak Smith
Member
I have a bunch of 6.8 data from an 18" barrel, but only with reloads and preproduction ammo. I don't have any actual production ammo yet. I can post it here or in a new thread.
-z
-z
10shooter
Member
I have two questions about the 6.5mm Grendel. Does the short stubby case length cause any feeding issues? And the width looks like it also would prohibit any true staggered magazines to fit the AR platform. I've been looking at both cartridges and would feel either is an improvement over the 5.56.
While I am fond of 6.5mm bullets for long range shooting I believe the 6.8
round created the most effective wound profile. Makes sense as it is a slightly larger bullet. It is a very efficient .270 light. - not ideal for elk but more then adaquate for deer size game.
I expect that this cartridge will become popular for civilians - it will allow the ar-15 owner to purchase a 6.8 upper to upgrade their 5.56 defense/varmit rifle to a deer rifle capability. End result - more "black rifles" will be seen in the woods during hunting season.
round created the most effective wound profile. Makes sense as it is a slightly larger bullet. It is a very efficient .270 light. - not ideal for elk but more then adaquate for deer size game.
I expect that this cartridge will become popular for civilians - it will allow the ar-15 owner to purchase a 6.8 upper to upgrade their 5.56 defense/varmit rifle to a deer rifle capability. End result - more "black rifles" will be seen in the woods during hunting season.
atek3
Member
Actually no. The designers started with the 43 mm SPC case, and picked the most effective bullet for that case, which was a stubby .277 cal bullet. Starting with a different case would give a different result.
atek3
Zak Smith
Member
Who has documented results from testing 6.5 Grendel in calibrated ballistic gelatin?
Grendelizer
Member
Zak, a certain suite of tests are scheduled for August 10. It is anticipated that some of the results will be made public, assuming that those who are paying for the tests are agreeable. I will post as much as I can.
This whole intermediate cartridge "movement" is a good. My theory remains that bigger bullet holes are better, and it's worth paying a slight weight and ammo reduction penalty for the increased wounding, range, and penetration. "Let the air in and the blood out." With the 5.56 it's already become standard practice, as I understand it, to "double tap." So instead of using one 265-grain 6.5 Grendel 123-gr cartridge, you've used two 182-gr 5.56s for 364-gr weight. (One 7.62 M80 weighs 386-gr.) Somebody might argue that even if we were using 7.62 they would still double tap, but my suspicion is that the practice arose in response to the 5.56's performance.
In combat, almost always your enemies are going to be behind cover. If every infantryman were given an intermediate cartridge with a better ability to penetrate cover than 5.56, then enemy casualties must increase as they are denied proportionally more cover. Fewer places to hide means more enemy casualties. And when they're all clustered behind some particular piece of cover that your better-penetrating bullets have herded them to, it's time for an airstrike! At least that's my theory, the military guys can respond.
John
This whole intermediate cartridge "movement" is a good. My theory remains that bigger bullet holes are better, and it's worth paying a slight weight and ammo reduction penalty for the increased wounding, range, and penetration. "Let the air in and the blood out." With the 5.56 it's already become standard practice, as I understand it, to "double tap." So instead of using one 265-grain 6.5 Grendel 123-gr cartridge, you've used two 182-gr 5.56s for 364-gr weight. (One 7.62 M80 weighs 386-gr.) Somebody might argue that even if we were using 7.62 they would still double tap, but my suspicion is that the practice arose in response to the 5.56's performance.
In combat, almost always your enemies are going to be behind cover. If every infantryman were given an intermediate cartridge with a better ability to penetrate cover than 5.56, then enemy casualties must increase as they are denied proportionally more cover. Fewer places to hide means more enemy casualties. And when they're all clustered behind some particular piece of cover that your better-penetrating bullets have herded them to, it's time for an airstrike!
At least that's my theory, the military guys can respond.John
Yes - you are correct - they did not pick the same case bullet as the Grendel. I don't think their objective was to pick best long range target round - but rather to obtain a more effective manstopper within expected combat ranges. I expect that even if they used a differnt case a larger diameter bulet would have produced better wounds (at least for humans - a 6.5 would be a far superior big game bullet for penetration from rear quarter, etc).
atek3
atek3
Zak Smith
Member
6.5 Grendel velocity predictions
Here's what I predict. Please correct me if you have chrono data that significantly differs:
The 108gr Sencar in 6.5 Grendel:
24" bbl - 2700 fps
20" bbl - 2600 fps
18" bbl - 2550 fps
16" bbl - 2477 fps
-z
Here's what I predict. Please correct me if you have chrono data that significantly differs:
The 108gr Sencar in 6.5 Grendel:
24" bbl - 2700 fps
20" bbl - 2600 fps
18" bbl - 2550 fps
16" bbl - 2477 fps
-z
TX65
Member
Here is what is measured on Oehler 35P chrono for the 108 Scenar
24 inch 2750 fps at 49,600 PSI - 2.25" OAL using AA2460, CCI 450 primer
18.5 inch 2700 fps
As far as terminal ballistics tests, they have been done and the appropriate parties are already in possession of the results and considering the possibilities for their applications.
The FBI test protocals are not same as the military. One series relates to law enforcement with their unique requirements and restrictions, the other is bound by an entirely different set of requirements and restrictions.
Edited To Add- There was a 30 degree difference in ambiant temp on the two days the different barrel lengths were measured - the 24 inch barrel was measured on the cooler day so velocity of the 24 inch would be closer to 2800 fps had they both been measured on the same warmer day.
24 inch 2750 fps at 49,600 PSI - 2.25" OAL using AA2460, CCI 450 primer
18.5 inch 2700 fps
As far as terminal ballistics tests, they have been done and the appropriate parties are already in possession of the results and considering the possibilities for their applications.
The FBI test protocals are not same as the military. One series relates to law enforcement with their unique requirements and restrictions, the other is bound by an entirely different set of requirements and restrictions.
Edited To Add- There was a 30 degree difference in ambiant temp on the two days the different barrel lengths were measured - the 24 inch barrel was measured on the cooler day so velocity of the 24 inch would be closer to 2800 fps had they both been measured on the same warmer day.
Last edited:
sumpnz
Member
You only lost 50fps going from a 24" to an 18.5" tube? I really like the Grendel, but color me sceptical.
Zak Smith
Member
I, too, am really skeptical that 6" of barrel only yields 50fps in a cartridge with a volume : bore ratio like 6.5 Grendel.
I would expect this kind of result in a low volume case with a fast powder because the residual pressure from 18-24" would be very low.
-z
I would expect this kind of result in a low volume case with a fast powder because the residual pressure from 18-24" would be very low.
-z
TX65
Member
Zak & Sump,,,
Read edit in original post,,,, difference in ambiant temperature...
Read edit in original post,,,, difference in ambiant temperature...
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