6.8mm vs. 7.62 mm long range rifle

[Maverick223]

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

Should have caught that...right you are (as usual).

Are you familiar with the Sierra and Berger hunting bullets?

Yep, but I don't use anything over a 180gr. for .30cal. deer hunting (though I do have a few 208gr. A-Max loaded for the .300WM if I should ever see the need for such a load). Furthermore I use anything from 168gr. SMKs all the way up to 240gr. SMKs for target loads (190gr. SMK is my "basic load") in my .300WM. Needless to say my little .30cal. Winnie will take the longest ones set out about as far as you'd like.

...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.

...but can you...and in field conditions? Either way the rifle isn't my point, the varying conditions and precise adjustments that must be taken into consideration is the root of the problem.

 

[1stmarine]

Everything starts and ends with the bullet. Understanding what the bullet does since you seat it until it hits the target it is all a very complex world of internal and external ballistics. The rifle and load are 90% of the equation and the other "90%" left is the eye (and my glasses LOL!), the scope and training.
I get an out of the box system and when I am done tuning it might look similar but it is a completely different system adapted to what I want to do.
I reload and test every single load/bullet/powder combination until I come up with something that works for MY SYSTEM and ME.
I use the 210grainer as it gives me the best BC possible and they buck the wind quite well.
I used to do the calculation by hand back in the service but after I learned and retired then I use a pocket pc since then. If the wind is over 7-10mph then I don't even take the shot regardless what the formula says and then move on closer if I can.

Cheers.
E.

 

[1stmarine]

I love ARs. Great to punch paper at 600 yards but we are talking about taking down a white tail at 800 yards. This is not the post for this.
By the way the only load in AR-15 platform that has the potential to outshout the .308 is the .30 OSSM but accuracy is not there. Power YES! Accuracy No.

In high power shooting I am very impressed with all the new BR cases, Grendel and so forth but this is meat and no paper we are talking about here.

Cheers.
E.

 

[1stmarine]

Sorry this is the post to talk long range. I was in a hunting one before and got sidetracked.
Somehow our track deviated to the whitetail in this post.
Cheers.
E.

 

[Float Pilot]

Wow, all you have to do is but 6.8mm into a thread title and watch the fur fly. I see the original poster from August has never chimed in since that time.

As to the original question, I own and have experimented around with a 6.8mm SPC (.270 caliber) to know that while it is interesting, it was never designed to be a super long range shooter. Granted I have a 16 inch barrel, but have experimented with a 20 inch as well.

The 270 caliber 130 grain Sierra Boat tails have a BC of .436 which is not really all that bad since a 308 caliber 168 grain Sierra Match bullet has a BC of .462.
But,, I can only get the 130s to go a little over 2,300 fps from a 20 inch barrel and 2,250 from a 16 inch barrel. And before the 6.5 Grendel guys get their sack in a twist, yes the 130 grain 6.5mm (264 cal) Berger VLD has a BC of .552, which works great in my 6.5x55mm Swedes or a .260 Rem, where there is enough powder to make them move at a high enough velocity to make use of the better BC.
As for the 110 grain bullets from the 6.8mm, I am chronographing the 110 grain Nosler Accubonds (BC of .370) at 2,550 fps from the 16 inch and 2,610 fps from a 20 inch.
All this is just fine for 300 to 400 yards, but that is about it...

The .308 Win pushing a 168 grain SMK ( BC .462) at anywhere between 2,575 fps and 2,700 fps, depending on the rifle and barrel length, will naturally be superior to the 6.8mm SPC at longer ranges.
Although as I am sure somebody mentioned in these 3 pages, the 308 is pretty well at its limit out at 800 to 900 yards.

I use a long barreled 300 Win Mag with 220 grain SMKs ( BC of .629) loaded to 2,890 fps for that sort of shooting or my 338 Lapua which is not very pleasant to shoot.

 

[NELSONs02]

.22 wmr

700 - 900 meters:

6.8spc - No
6.5 creedmoor - Why?
6.5 Grendel - AR
.308 - sure
6.5x47 - Ok
.260 Remington - Where it's at

 

[henschman]

For the ranges you are talking about, the 7.62x51 is superior in almost every way to the 6.8 SPC.

The ideal barrel length for these ranges would be around 22" IMO.

As others have pointed out, there are some commercial rounds that offer better ballistic performance than the 7.62 NATO. However, the 7.62 offers decent performance at these ranges and is cheap if you buy commercial or surplus, and offers a lot of options when it comes to handloading as well.

 

[1stmarine]

The 6.8 in a SPC case cannot do it even with the 130gr. Not even close to the starting point of long range.
The only 6.8 that I would consider that can chanllenge the .308 win is the 270 Winchester given that you use a Hornady or VLD of 150gr and BC. of .530
This will keep you supersonic past 1000 yards and with some energy to kill white tail between 700-800 yards and other smaller critters past that point.
The nice thing about this round it is a tad flatter shooting so if you do not need more energy at 1000 (for paper or steel) this is a good one.

For the .308 Win check this bullets. Berger VLD 190gr (BC.570) if you do not mind a higher ballistics parabola. In the ideal day you can reach 1000 yards with a hunting load supersonic and with plenty of energy left. It is of course a hot hunting load and already pushing it for the .308 but it can be done with good brass bullets and reload skills. I use it and always keep a few dozen loads ready to go. I reload from the hornady .308 match and tap once fired brass with great results. I would not go below 175gr. 168gr for 700 yards and much flatter.

The 7.62 NATO (.308 Win) it is certified in the military with sniper ammo SMK 175 ( military M118LR - LR for long range) to have a sure kill at 800 meters (870yards). It can be done further and with a bit of help from conditions and luck. The Sniper Military loads might be very stable and work well in artic to desert environments where the same day the temps can go from 10 below at night to 105 degrees during the day and the sniper load will have to be consistent and do the best in either scenario.

If you want more look into the magnums, there are many good ones. Do not need to go to .338 to make 1500yards hits as there are many good choices in the .308.

Winmag is pretty good but up to 200gr. I suggest for 200gr to 250gr I would use the RUM and for anything beyond then 338 lapua, BMG others but there are many things you can achieve with the RUM with 1/4 of the budget of lapua/bmgs. In the end there are very few things that can be done with the lapua that cannot be done with the .30 RUM with a 240gr bullet of ballistic coefficient of .711 for much less dollars. What kills the RUM marketing is the lack of good out of the box systems. There are good rifles out there but they need some serious work. When you are done you will be pleased and it will be WAY less expensive than the big guys anyway.

In the post I saw the 6.8mm vs. 7.62 for long range and nothing mentioned about the AR-15 so I would agree that the 6.8 130gr it is a decent bullet but I don't think that you can seat this into the AR 6.8 SPC round w/o going over the limited OAL. Also why to stop in the 6.8 when there is a much better selection in the 7mm and even the 6.5 before. Anyway if the 6.8 is in the SPC case then you are doomed for long range. If you are in an AR even worse since the 110-115grainers have some of the worse ballistics out there.

Hey! the AR 6.8 are great systems like all ARs for shorter range but after the 250-300 yards the round drops straight to the ground so, as many ballistics experts agree, it was the wrong choice in diameter and OAL case. Check the ballistics. I think that Remington got some bad SOCOM advice and this will not make it trough any trails. With some more recent and real life advice from infantry they are working in a lighter yet powerful new round. I can see a nice niche for the average use in 6.8 and obviously far superior in short range but the military has been very demanding more versatility and less weight. One of the things that made the M16 so popular is the fact that each squad member in patrols in Vietnam would carry 600+ rounds any day.

There is an olympic case the .30 OSSM by Olympic that showed some potential in the AR-15 but initial reports are not very promising. It looks more all about power but accuracy is not there. Also the OAL doesn't allow for bullets with high BC so like with the 6.8 it destroys the longer reach potential.

In the AR-15 there are many good options but it is what it is. In the end we can try to put a Corvette engine inside a Geo Metro w/o changing the chassis and we might do something but we will always run into problems.

ARs, AKs, Bolt... I like them all!

Cheers,
E.

 

[Zak Smith]

E,

We've strayed a bit off topic.

For long-range in .308, you might find it interesting to run the numbers for a 155 Lapua Scenar at 2900-2950 fps. BC 0.509. Actually, you will be hard pressed to find a LR .308 load that beats it. It's been my LR .308 match load for about six years.

-z

 

[1stmarine]

... I forgot.. In case you can choose in the 6.5mm shelves....
Also the grendel is a great round somebody mention before.
The grendel can punch some paper but forget about hunting at those ranges other than squirrels.
The .260 is a much better option in 6.5 but you need a SMK 142gr and in the AR it has to be AR-10 with a long barrel.

I hope this helps.

 

[1stmarine]

Yes Zak. How we could forget the venerable scenar and palma cases?
I was concentrating on the hunting loads because it is what I do and in the post there is no mention of purpose. Maybe I should ready the entire post!!

Awesome choices you talk out there. whatever caliber you choose it is clear everything starts and ends with the bullet.

Was the purpose target or hunting or either?

Cheers.
E.