6.8mm vs. 7.62 mm long range rifle

[wanderinwalker]

If your options are only the 6.8 SPC or a 7.62 NATO in a long-range rig, get the 7.62 NATO and never look back. The 6.8 throws short, stubby low-BC bullets at moderate speeds, while the 7.62 will throw a longer, higher BC bullet at moderate speeds. Actually, a 155gr Palma bullet can do 3000-fps in a .308 with enough barrel length and is a proven 1000-yard load.

Now, if you are open to other choices and are a handloader, get a 6.5mm round and go shoot happier. Higher BC bullets will buck wind better and drop less at any given distance. IMO, the best 6.5mm rounds use the .308-case head (6.5 Creedmore, .260 Remington). Another option is a 6mm AR if you went to stay on the AR-15 platform. It's basically a necked down 6.5 Grendel, and should be good at launching 107gr Sierra Matchkings.

But like Maverick223 says, don't overlook a .223 with the long, heavy bullets like 80gr Sierras and Noslers and 75 and 80gr Hornady A-Maxs, or even the Berger VLD bullets. These are single-load only with fast-twist barrels, but I know from experience the 80gr Nosler will shoot great to 600 yards from a match-prepped AR-15, and is a lot cheaper than a bigger gun.

 

[Tirod]

And why does anyone shooting 600M+ even use a 100m zero? What the author of the linked article showed was that either caliber zeroed for the correct distance it was to be shot at will have less than a few inches difference drop. They will both hit the same paper plate.

The purpose of the article is very much to compare apples to apples and then see exactly what the difference is with bullet diameter and length. There's plenty of evidence to understand that a smaller bullet has less surface area to absorb energy - which is why smaller calibers travel slower than larger ones WHEN OTHER THINGS ARE EQUAL.

As for the concept of "ballistic coefficient," remember that it's calculated number that is used to understand the dynamics of ballistic flight. It does not represent a physical quality that is guaranteed to be superior the larger it is. ALL bullets drop, it's how you use them that makes the difference. If a bullet is to travel over long distances, it can either use a design that loses less energy, or it can have more mass to retain energy longer.

The .308 will offer both, a good selection of bullets with low energy loss shapes, higher mass, and enough powder to get it moving out of the barrel with sufficient initial speed. The 6.8 could be set up for the job, but ballistics favors the .308 in the same way it favors the .50 BMG.

BTW, I've been accused of stalking threads with antagonistic banter about the 6.8 where it wasn't necessary to the OP's question. I'll offer one guess who was a bit righteous about pointing that out. Et tu?

Well, it's nice to know that one 6.5G enthusiast agrees that the caliber has no business trying to do or be what the 6.8 SPC is. What's sad is that since the two calibers are a lot more alike than different, and that the 6.8 has rarely attempted a comparison with larger calibers, the 6.5G needs to see the futility of attempting it also. It can't be, it doesn't load 180gr + rounds with 45gr of powder and have over 50 years of development.

If long range is the end game, the .308 is the better cartridge, and it still demonstrates it.

 

[Maverick223]

There's plenty of evidence to understand that a smaller bullet has less surface area to absorb energy - which is why smaller calibers travel slower than larger ones WHEN OTHER THINGS ARE EQUAL.

Not true, the bullet is "squeezed out" by the pressure, not simply pushed out. The reason that a larger caliber bullet of the same weight propelled by the same volume of powder (from the same case) typically exits the muzzle faster than a smaller one is because the larger bore can extract most of the energy from the propellant, whereas the smaller bore retains higher pressure longer and wastes slightly more energy (which is expelled out the muzzle). Given a longer bbl (to equalize the pressure equivalent to the larger bore) for the smaller caliber there is absolutely no difference in performance, at least not from an energy standpoint (there is a difference in trauma/cavity volume, which is greater for the larger caliber, and penetration, which is greater for the smaller caliber as a result of the higher SD).

 

[longdayjake]

What the author of the linked article showed was that either caliber zeroed for the correct distance it was to be shot at will have less than a few inches difference drop.

That would be true only if the numbers he used for the grendel weren't skewed to get that specific result. In any case, it isn't true. I thought my post about the article had pointed that out sufficiently.

If long range is the end game, the .308 is the better cartridge, and it still demonstrates it.

Be specific please. You make an assertion now try to back it up with proof. I will admit that it does carry more energy and therefore more killing potential, but the 6.5 can punch paper as good or better. That said, there are better rounds for long range than the 6.5 grendel.

BTW, I've been accused of stalking threads with antagonistic banter about the 6.8 where it wasn't necessary to the OP's question. I'll offer one guess who was a bit righteous about pointing that out. Et tu?

I admit. I pointed out the fact that you stalk 6.5 grendel threads just to throw in something about the 6.8. I wouldn't mind so much if you EVER posted ANYTHING to prove your claims. You have yet to do so. You say things as though they are true and expect everyone to believe you because you utter the words. You can hate me if you wish but I am going to continue hounding your biased statements until you back them up with proof.

As an aside, the OP asked what would be better for long range. I suggested the .308 for long range. I said that the 6.8 drops really really bad past 700 yards which is true. He said he wanted to go out to 900. I assumed that since he only gave options in the AR platform that he would want something for the AR. I figured that since his main focus was long range that it wouldn't matter what caliber as long as it did the job well. Aside from the .260 (which is almost impossible to find in the AR in a reasonable amount of time) the 6.5 grendel can shoot long range really well and it can do it in the ar15 version instead of the ar10. If the OP wants a long range AR I think he should order a .260 and wait the year or so for them to be available or he could buy a 6.5 grendel and hold just a little higher. The .308 is a great cartridge but as far as potential accuracy is concerned the 6.5 bullets give the grendel a little edge. (On paper)

 

[stiletto raggio]

http://demigodllc.com/articles/practical-long-range-rifle-shooting-equipment/

The .308 is a good choice simply because there has been so much R&D put into it. The .308 obligates you to a larger and heavier rifle. The 6.5 Grendel will hang with the best-loaded .308s in terms of raw ballistic capability, but it really has an advantage with BC compared tot he 6.8. Yes, there are a lot of variables to consider, but to quote the above article,

"There are two primary factors related to caliber which affect long-range performance. The first is the bullet's Ballistic Coefficient (BC), a measure of how easily the bullet slips through the air. Higher BC is better. The second is the muzzle velocity. Faster is better."

If we are comparing apples to apples and the ammo used is all of the same quality and consistency, and the same is true for barrel quality and other variables, the round that can push the bullets with the highest ballistic coefficients at the fastest speeds will have an advantage. Flat trajectory isn't everything; there are guys who can shoot .45/70s at very long range and hit what they aim at. But BC also indicates how long a bullet will remain supersonic, and that can have a real impact on accuracy.

 

[longdayjake]

The .308 is a good choice simply because there has been so much R&D put into it.

Very good point. Of the choices given the .308 definately shines as far as published data and quality equipment goes.

 

[Girodin]

For what you want to do, either punching paper or taking game, I suggest an M1A rifle or a good bolt gun in .308.

The M1A for a 1000 yd long distance shooting gun strikes me as an odd suggestion.

See this thread for lengthy discussion. http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=1799323&page=1

IMO the .308 is better for the task you have defined than a 6.8. If it is a choice between those two then I'd get the .308. A .260 rem is and advantage over the .308 and available in the AR platform if you really prefer that platform to a bolt gun. Unless you hand load, however, I would not get the .260.

 

[Tirod]

I admit. I pointed out the fact that you stalk 6.5 grendel threads just to throw in something about the 6.8. I wouldn't mind so much if you EVER posted ANYTHING to prove your claims. You have yet to do so.You say things as though they are true and expect everyone to believe you because you utter the words. You can hate me if you wish but I am going to continue hounding your biased statements until you back them up with proof.

I believe you have nailed it very well. It's exactly the problem with most of the posts I've read on the 6.5G, over wrought absolutes about how the 6.5G is always better than 6.8 or .308. It's never backed up with any chronographed results from your guns, no side by side demonstrations, just out of context quotations of someone else's calculated data. Any valid comments by others are always "biased," and the opinions and data presented by experts to show what's really going on are always ignored.

I've deliberately avoided most 6.5 discussions because I DON'T OWN ONE. Same with .22-250 and a lot of others. Since the 6.8 doesn't seem to be a apart of your future acquistions, we really should cross paths rarely - but, here you are. If you intrude on discussions not germane to your avid interest, expect to be called out on the dogma and distortion. It's what you do.

The proof of my statement that .308 is better - already answered in the above posts, it's common knowledge and referenced. And having posted this, I see you now agree? Not hard to find at all - which is what happens when others also see bad information being put out contrary to sense. I don't need to repeat it.

The issue of the 6.5G is coming across as an egocentric one, not an examination of what caliber would be appropriate. As each occasion arises, the same themes get repeated: 6.5G is better, it's superior to bigger calibers, my statements are pure truth, why the bias, and now, I'm going to hunt you down.

I'm putting it right out there, this obsession with 6.5G is not only damaging the reputation of other enthusiasts, it's a window showing areas of serious concern. The 6.5G isn't the subject here, further discussion is off topic.

 

[Maverick223]

I'm putting it right out there, this obsession with 6.5G is not only damaging the reputation of other enthusiasts, it's a window showing areas of serious concern. The 6.5G isn't the subject here, further discussion is off topic.

I disagree, if someone believes the 6.5Grendel (or any other cartridge) to be better it should be brought up, unless the OP specifically states that he is not interested in other options. I agree that the 6.5Grendel is a good option, as is other options (including, but not limited to the .223Rem. with a long fast twist bbl, .260Rem., and 7mm-08Rem.). If I were the OP, I would appreciate any reasonable additional suggestions and information brought forth, whether I decided they were valid/applicable in my case or not.

 

[Zak Smith]

Anything you can fire in an AR-15 from a double-stack magazine is limited ballistically by its case capacity. There is no getting around that. The .308 (even when loaded to its ballistic best) isn't even a very good long range cartridge-- it is marginally competent, but ubiquitous due to history.

-z

 

[Maverick223]

The .308 (even when loaded to its ballistic best) isn't even a very good long range cartridge-- it is marginally competent, but ubiquitous due to history.

WOW!...someone that actually agrees with me...and I already know you're a big proponent of the .260Rem. How do you feel about the 7mm-08Rem?...or my favorite medium cartridge, the .280Rem?

 

[longdayjake]

Zak is the man.
Take what this guys says about long range seriously. Its coming from the same guy that wrote this article. http://demigodllc.com/articles/practical-long-range-rifle-shooting-equipment/

 

[Warfarin]

I say buy a Mosin Nagant M91/30. They are cheap, they reach out to 1000 yards no problem and ammo is cheap.

 

[Maverick223]

I say buy a Mosin Nagant M91/30. They are cheap, they reach out to 1000 yards no problem and ammo is cheap.

You're joking...right? Not knocking the MN, it is a decent rifle for what it was built for, but it is far from a long range target rifle. Just because the sights go up that high, doesn't mean the bullet will (for inspiration just take a look at standard AK sights). Oh, it'll get there...somewhere out there at 1k yds, give or take a few dozen.

 

[Gamer1524]

How was the LWRC

 

[Gamer1524]

For one second here I would like to go back to the author and what he is wanting this AR platform for...do you want to hunt? punch paper? Bragging rights....as for the ranges We are really looking long distance here...I might throw out two other rounds depending what he wants to do...if you want to punch paper I might offer up the the .204....very fast...over 4000 FPS with a light load...and very accurate....want some knock down power then you might think about the .338 Laupua...expensive to shoot...but it will get you out there.

 

[Tirod]

It's really been asked and answered - 6.8 or .308. Sure, other cartridges could do the job, whatever that is, but between the two the OP specifically mentioned, the .308 will do a better job.

That doesn't mean just because the DOD has it in inventory it's the BEST - that has already been established long ago, the .50BMG does it better than any other. It's also the accepted upper limit in feasible single operator firearms. This well known and accepted fact is largely ignored in these discussions.

The usual checklist of My Favorite Caliber always seems to come up, they quite often veer off into a caliber war unrelated to the OP's question. It's not HIS fault other posters bring up alternate choices, but it can be insulting. It's as if they think he's incapable of drilling down his personal preferences and resources to establish a short list. Nonetheless, plainly posted, it exists right out there first up.

Lot's of us don't post alternatives for that reason and others. Give the OP a straight up answer and stay on topic, threads won't get derailed with agendas and misinformation (pick your point of view) about what was never mentioned. No sense being the first and foremost author going off topic with another chapter in extremism.

Why .308? Like Zak said, it's around. It's cheap, developed, has lots of support, handload data and components readily available, and does the job. 168gn open tip boat tails are the standard long distance bullet of choice since they were practically invented. It's not that the 6.8 can't be made to do it, it will only use up to 130gn bullets, few to none developed for it specifically. Paper or blood, the .308 is a lot further down the developmental road with specific solutions to specific applications. It's really a no brainer.

The 38 grains of extra weight has a lot to do with it, don't let the contrived number of BC get too much in your thinking. It's a calcuated form factor based on bullet diameter and drag coefficient derived from doppler radar measurements, not a literal number. It's also announced by the manufacturer in almost every case, not an independent lab or institutional clearing house. In other words, there is no guarantee marketing hype doesn't affect the number.

Those who know their stuff about hot rodding see this in carburetor CFM ratings, cam duration, and we are all pretty familiar about the hype surrounding horsepower ratings. NONE of it can be taken literally, and it's naive to do so. Ballistic coefficient is what the makers want it to be.

 

[Zak Smith]

.308 175 grain sierra match king M118 shot at about 2600 fps (24" barrel velocities) BC of .505

...

6.5 Grendel with 123 grain Lapua Scenar shot at 2620 (AA data from 24" barrels) BC of .547

Why is it that when comparing long-range loads against 6.5 Grendel, the .308 load chosen is always a really marginal load than nobody - who has a choice - competes with any more; whereas the 6.5 Grendel load is the best possible LR load for it? That's a pretty contrived comparison.

Here's a more realistic comparison, with .260 Rem thrown in for fun

_Bullet_           _BC_ _MV_         0     200     400     600     800    1000 | YARDS
308 155 Scenar    0.508 2930 >    0.00    2.27    9.66   23.18   44.10   73.97 | wind (inches)
308 175SMK        0.51* 2700 >    0.00    2.62   11.18   26.93   51.55   86.72 | wind (inches)
308 175SMK        0.51* 2600 >    0.00    2.77   11.81   28.48   54.58   91.64 | wind (inches)
260 123           0.545 3050 >    0.00    1.99    8.42   20.08   37.95   63.27 | wind (inches)
260 139           0.615 2900 >    0.00    1.89    7.93   18.79   35.26   58.34 | wind (inches)
6.5G 123          0.545 2630 >    0.00    2.46   10.44   25.00   47.44   79.05 | wind (inches)
6.5G 139          0.615 2400 >    0.00    2.47   10.42   24.80   46.70   77.05 | wind (inches)

308 155 Scenar    0.508 2930 >   -0.00    0.36    1.67    3.35    5.42    7.97 | drop (mil)
308 175SMK        0.51* 2700 >   -0.00    0.48    2.07    4.11    6.66    9.84 | drop (mil)
308 175SMK        0.51* 2600 >   -0.00    0.54    2.27    4.50    7.28   10.75 | drop (mil)
260 123           0.545 3050 >   -0.00    0.30    1.47    2.96    4.76    6.93 | drop (mil)
260 139           0.615 2900 >   -0.00    0.36    1.63    3.22    5.10    7.32 | drop (mil)
6.5G 123          0.545 2630 >   -0.00    0.51    2.15    4.23    6.75    9.83 | drop (mil)
6.5G 139          0.615 2400 >   -0.00    0.66    2.62    5.02    7.90   11.33 | drop (mil)

308 155 Scenar    0.508 2930 >    2930    2593    2281    1992    1726    1490 | velocity (fps)
308 175SMK        0.51* 2700 >    2700    2372    2069    1791    1536    1320 | velocity (fps)
308 175SMK        0.51* 2600 >    2600    2280    1984    1712    1468    1266 | velocity (fps)
260 123           0.545 3050 >    3050    2728    2426    2146    1886    1647 | velocity (fps)
260 139           0.615 2900 >    2900    2622    2360    2115    1886    1672 | velocity (fps)
6.5G 123          0.545 2630 >    2630    2335    2062    1808    1577    1376 | velocity (fps)
6.5G 139          0.615 2400 >    2400    2152    1920    1704    1510    1339 | velocity (fps)

 

[vaupet]

I know nothing of the subject, except that there are three great articles on long range shooting in the library sticky on this Rifle Country page. Cover about every aspect.

 

[1stmarine]

That is an easy one...

In .308 you have some of the best (if not the best) selection of bullets you can find including High BC (Ballistic Coefficient) which is what you want.

In 6.8 is one of the worse plus you pay more for some bullets. Also you can use military bulk . 308 packages to shoot shorter ranges with the same gun.

So if you want to do long range (or anything for that matter) first start with the bullet selection. With 900yards you are looking for bullets around .55 BC and above. Now depending on what you want to do at those ranges you need to decide on speed and grain. Then you can decide on the rifle. If you want to hunt at 900 yards then this is too much for the .308 and about ok for 30.06 all reliable and affordable cases. If not you need to jump to the magnums and short magnums. Don't get much more speed that what is needed since it will cost you in barrels, brass and powder.

At those ranges to be accurate you are probably talking about some expensive systems around .25MOA and better.

I hope this helps.

 

[Maverick223]

If you want to hunt at 900 yards then this is too much for the .308 and about ok for 30.06 all reliable and affordable cases.

Not hardly...the '06 is fine for 900yds....if you are hunting paper, or perhaps a coyote...but it ain't a deer rifle at that range. First and foremost a great deal can happen in the 1.5sec. that it takes for the bullet to arrive. Additionally about 750ft*lbs of energy and 125 optimal game weight isn't exactly ideal for anything but a perfect shot...which isn't going to be likely at 900yds with any rifle...but lets forget about energy figures and such for a moment. To put that shot in perspective, a 1.0 MOA rifle would place you about 9.5in. off POA without user error (you can forget about a quarter MOA deer rifle...it'd weigh 20lbs...most folks just wouldn't hunt if burdened by carrying such a beast). And don't forget the nearly 20ft. of vertical drop and 3ft. of windage.; and that's at a mere 5MPH...get a 2MPH gust (or miscalculation) and you'll be off by over a foot laterally. So even with the best gear you better know your windage perfectly, not only at the muzzle but at the target and between...and quick enough to still have a shot at your quarry. Still think you can make that shot?...reliably?...ethically?

That said, I completely agree with your assessment on the bullet selection, the .30cal. is much better in the bullet dept., and IMO a better caliber all-around (though I like a nice 6.5/7mm).

 

[Zak Smith]

To put that shot in perspective, a 1.0 MOA rifle would place you about 9.5in. off POA without use

If the rifle is zeroed at the center of the group, you would expect max approx 4.7" from POA.

 

[1stmarine]

I would agree with you that a magnum is more appropriate for long range hunting but it can be done with 30.06 and with one advantage over the WinMag for example. It can take the heaviest (better) bullets w/o any neck issues. Last year in texas I took 2 with my 30.60 savage one at 690 and the other at 870yrds w/o any problems. both shots through the lungs and they just collapsed right there. Of course one needs a good hunting load. You obviously cannot use over the shelve core-lokts. Are you familiar with the Sierra and Berger hunting bullets?

This is what I am getting with the 210grs. bullet. Plenty to kill whitetail unless you want to kill it twice...

Range Velocity Drop Energy
0 2520 0 2961
100 2382 3.1 2646
200 2252 12.35 2365
300 2125 28.5 2106
400 2003 52.37 1871
500 1885 84.94 1657
600 1772 127.31 1464
700 1665 180.76 1293
800 1563 246.73 1139
900 1468 326.89 1005
1000 1379 423.12 887

My scope is a Monarch 6x24.

 

[1stmarine]

...I forgot My Savage prints .25 MOA groups all day long with that load. Had issues at first but spent some money and had an harmonics tuner installed and now it shoots like a bench rest one.

Cheers.
E.

 

[earplug]

AR 15 platform such as used in NRA high power competition. In 223 600 yards beats 308
No this is not 900 yards. But with a really good scope and practice you will do fine.
If your shooting at people your not round count limited. Its all comstock.