oh they are going to let it rip alright. . . .
there ar going to be no replacements to the 5.56.
the 6.8 spc, 6.5 grendel, 300 aac blackout, .30 rar, .450 bushmaster. 50 beouwolf, .458 socom etc etc etc were all designed to work within the length and width requirments of the ar15 magazine. followers may need changed in some ofr 100% reliability.
they are all commercialy available and for the most part have sammi specs. they chamber the ar in smaller rounds such as the 204 also. just get what suits your needs if you dont like the 5.56 but dont expect cheap surplus ammo in the future.

btw i predict much heated debate will follow, just decide what you are needing and base your decision on that. they are all great rounds within their intended roles.

 

Yes, it is a wrong assumption that they all use the same magazines. Only .300 BLK and .300 Whisper use the same mags as 5.56 NATO. BLK's close to 7.62x39 with a lower MV and a higher BC and Whisper is downloaded slightly compared to BLK. The 6.8 SPC was designed to perform better than 5.56 NATO at all ranges and to have a slightly larger range than 5.56 NATO. 6.8 SPC II is the most recent development and seems to fix most of the problems with the 6.8. The 6.5 Grendel was designed to have the longest effective range out of an AR-15. It will surpass 7.62x51 and 7.62x54mmR in energy at longer ranges because of its better BC.

 

the 6.8 SPC spec II is a chamber specification, and did not accompany any changes in actual ammunition. the new chamber specs help to make the round more efficient (a little more MV), but its not a massive change in performance.

while the BC of 6.5 might help the trajectory compared to the .308, the 6.5 never actually has a higher energy then .308 even out to 1000 yards, .308 still has over 460 ft-lbs of energy whereas the 6.5 only has 350... see the 8th column in the chart below

 

Im a little more comfortable with the 5.56 now than I was when I first got an AR. But shortly after getting an AR, I got an upper in the 6x45mm. At the time Corbon was the only one offering ammo for it. Its still not a very commonly available caliber commercially loaded and it has never really caught on. Its still out there today all though the uppers for them not so much. Both are kind of pricy when you do find them.

Its a good option if your a reloader though! Ammo is very easy to make. Your just running it through a die to expand to 6mm caliber and then following your normal routine from there on 5.56 brass. The only thing changing is the caliber of the projectile to be loaded in it. Its a very good performer with bullets in the 75-90 gr range, giving a pretty good balance of trajectory, velocity and its a down range improvement over the 5.56 by a good bit. You can go heavier but then the velocity drops a good bit and the bullets were designed to perform best at the higher 243 Winchester velocities. I have taken an occasional Deer with it and I have put a lot of Hogs in the freezer with it over the years. With some of the better bullets being made for the 5.56 though that advantage isn't nearly as great as it was 15-18 years ago, but some of those bullet designs are now available for the 6mm too! Recoil is still quite mild making all day at the range a Sunday afternoon walking in the park and just as importantly being able to quickly get back on target after the shot so you can put warheads on foreheads. Weight of the ammo hasn't increased much over the 5.56 nor does the capacity in a typical AR mag get reduced as it has for the other options often available. Its one of my favorite options to the AR caliber delima and one that I cant understand why its not more popular. My upper is a 16 inch heavy flutted barrel with a 1-9 twist rate making it quiet handy to maneuver with and quiet the tack driver out to 300 yards. I can hit well beyond that but I think its a rock solid 300-350 yard hitter!

Here a link with a little more history and information. It is wiki so...it may not be the most definitive write up....

http://en.wikipedia.org/wiki/6x45_mm

For a cheap harder hitting alternative to the 5.56, I think the 6x45mm is the best option and a winner if ever there was one.

 

I'd also throw in the 6mm PPC, the well regarded benchrest round, also available in the AR platform.
http://www.model1sales.com/index.cfm?fuseaction=category.display&category_id=173

Since I already have what is essentially the 6.5 mm PPC (the 6.5 Grendel), I would vouch for it.

 

School me on this - and don't offer the 7.62X51 as I have that available and Im interested in the possible military use of the 6.8 or similar. AND in which of these "wildcats" are now commercially available?
Thank You and let er rip!

6.8 SPC is ballistically quite similar to 276 Pedersen (original chambering for the Garand) and 280 British (the round NATO should have standardized on instead of 7.62x51) -- not really anything new under the sun.

Outside of the thumper type AR caliber options, probably all the options are workable service rounds (I have some reservations about the case geometry on Grendel, but I'm sure someone will be along soon enough to explain both Jesus and his Father hand delivered the design to Bill Alexander -- but regardless by "reservations" I don't mean "trash" I just mean I think it might present issues if run often enough and rough enough in enough guns to get a valid statistical sample).

If you mean for SHTF use -- for any of them, stock up, since you may or may not ever see anyone else using them once things go pear shaped. The fact that you are unlikely to be able to beg, borrow, or steal more ammo may be an issue for some. With an AR, OTOH, you can always stock a 5.56 upper as well and it's less of a problem.

 

I dont know your financial situation, but 6.8 is about $1 a round. And if you reload good luck finding small primer brass ( rem makes large primer 6.8 brass) and the brass you do find with cost .50 cents a peice

plus side it has good knock down power and despite what most say about reaching out and touching something with the caliber, there Is a few 140gr loads that have a high BC and paired with PRI mags become a very capable round at 800.

The 556 is cheaper in cost to purchase and to reload for and the 77gr smk out a 1-7 twist is a very good round at distance

the 6.5 grendel is something ive been looking at just because it stays supersonic out past 1200 meters , but the ammo is $1 and I havnt looked toomuch at the reloading side of it but I assume its hard to find brass ect, honestly idk if I would get a 6.5 as my first ar15 caliber

300 blk is good but unless you reload FORGET about it , gotta make your own brass or pay for it and thats $$$ but that may not be a issue for you plus a youtube video serch will show you why the 300 blk was created QUIET when supressed


This is my personal opinion and limited experience on the calibers so take it for what it is opinion

I would sugest getting a 556 caliber and go from there its a very good caliber and common , reloading for it is simple and cheap

I love 6.8 but its way to hard to find ammo and when I do I cant go out and buy 500 rounds without sacrificing other areas I prep in, then forget about buying brass for it other then that its NICE

300 blk is on my list to build a upper in

and 6.5 is onmy list to build a whole gun around


Hope this helped

 

The 6.8 is the result of the Army's AMT, Remington and SOCOM. The 6.5 is the most accurate and the 7 has the best terminal ballistics; the 6.8 is a compromise of the two.

Ammunition isn't as common locally as the 5,56 or the 7,62 or 5,45 x 39 and it is more expensive. My personal preferences lean towards accuracy, flat shooting, and excellent terminal ballistics; here the 6.8 delivers. In addition, it is a fun, low recoil, accurate round. That being said, IMO, if you are looking for a single rifle solution; the 6.8 isn't it.

 

6.8 is NOT $1 a round. I just bought some, it can be had for .64/round (110 grain FMJ) if you bought 1000 rounds.

The difference in ammo prices is in the plinking ammo. High end ammo like the 77 grain Silver State Armory OTM (Mk. 262 clone) in 5.56 costs about the same as the Federal/ATK 90 grain Gold Dot in 6.8x43.

For me, the improved performance of the 6.8 is worth the extra $.

 

Where is it .64 , and is it S&B?

I have been getting SSA and hornady , never tried S&B

 

Look at it from a reloading/ballistics standpoint...

The most common 5.56 load is a 62 grain bullet moving at approximately 3000 FPS, plus or minus a hundred depending on the rifle, air conditions, etc.

Assume 3000 for a baseline. A 62gr bullet moving at 3000 FPS generates approximately 1238 ft/lb of energy.

Now, look at the 6.8SPC. Loaded with 130gr Spitzer bullets, they move at an average of 2500 FPS. That round will generate approximately 1803 ft/lbs of energy.

A difference of almost 600 ft/lb is not insignificant.

That said, a heavier bullet moving at a lower velocity will have more of a "lob" type trajectory, compared to the 5.56's nearly LOS (line-of-sight) trajectory out to approximately 300m.

So, is a heavier bullet moving slower better than a smaller bullet moving faster? I really don't know.

Both rounds have their place, in my opinion. I won't venture to say that one is better than another, however.

 

Although the 5,56 fragments; the fragmentation is speed dependent; within its envelope it is quite effective. The 6.8's terminal ballistics are for hunting.
At 350 meters, the 5,56 loses its fragmentation and hunters using the 6.8 will see expansion.
As most folks buy the M193 or SS-109; they aren't shooting 223 varmint etc ammunition.

My 5,56 have a Wylde chamber sort of a compromise which supports shooting either 5,56 or .223.

 

6.8 mag followers, and bodies are slightly different... the indent on the sides of the mag need to be shallower then a 5.56 mag... hence if you try to load a 5.56 mag with 6.8 the front end of the rounds will pinch together.

 

My next upper will be in 6.5 PCC (yes, PCC). Its just a 5.56 case necked up to 6.5 and shortened to 1.630. Once fireformed, it has about 33ish grains case capacity of water. Loaded to 56,000 PSI, it should have no problems pushing a 123 SMK 2400 fps from a 20 inch barrel or a Barnes 100 TTSX to around 2600 fps. I am really looking forward to hunting with it.

 

My opinion?
5.56 works great.
When it WON'T work, buy a .308.
When that won't cut it, buy a .300WM.
If that won't work, you're in Africa and should ask the PH what caliber is their minimum and what they recommend.

 

There was the old standard for 6.8 under SAAMI is underpowered due to a faulty chamber drawing submitted by Remington and the wrong barrel profile, also submitted by Remington. The round succeeded despite Remington, really.

If you have an SPCII barrel (as most of them now are), you have no worries. That new Federal 90 Grain Gold Dot gets 2850 fps out of a 16" barrel. That is the kind of performance Remington gave up on without even trying.

 

Bingo.
Remington is well known for screwing up a good thing. Another "fine" example is the original 244 with the wrong rifling and 243 with the right rifling. The rest is history.

 

My FAL is a ~1.25 MOA rifle, so it is needed. Add the optics and ammo, it weighs more than an empty rifle.

The SCAR 17 is 7.9# empty; did you plan on carrying it empty? With small arms, the weight of the weapon isn't much when compared to the ammunition and extras.

Btw, the lady of the house worked in engineering at FN Mfg in Columbia, SC.

 

I just weighed a SCAR17S.

8.1 LBS ( Bare rifle)

M68 CCO / mount= .6 lbs
M150 ACOG = 1.1 lbs
M145 Elcan= 1.5 lbs
Leupold VX1 1-4×20mm scope= .7 lbs ( Leupold qd rings med= .06 lbs) Total combined weight at less than 1lbs.( .76lbs)
SWFA SS 10X scope = 1.31 lbs

M14 sling= .05 lbs

SOCOM762-MINI2 = 1.06 lbs

M646 NVS 3gen + = 2.06 lbs
AZ-7 TIS = 1.4 lbs

A loaded Scar17 20rd magazine ( Q3130) = 1.6 lbs

100rds Q3130 Win 147gr fmj ( A more consistent M80) = 5.20 lbs
100rds AO 165gr SGK = 5.31 lbs
100rds A76251M1A 168gr OTM ( AE ) = 5.33 lbs
100rds BH or ASYM 168GR TTSX= 5.33 lbs
100rds BH 175gr TMK = 5.4lbs

Note:
Firing pin broke at exactly 2332 rds fired. 45 bucks to replace it. ( Scar17s)

I would keep that FAL btw. .......
No need for 5.56mm, 6.8spc, 6.5 grendal, 300aac , 458 Socom, or 50 beowolf.....etc

 

http://ammoseek.com/ammo/6.8mm-remington

Currently $0.61.4 per round is the cheapest.

 

another newbie resurrects another necro thread

 

There's nothing wrong with continuing a long-paused conversation.

Fragout's post about weights and longevity was interesting and relevant.

 

The long and short of it...personal preference.:thumb:

 

Oh the 6.8 will kill someone twice, and make it more painful too.

 

Think of the difference this way. They are both intermediate rifle calibers. They perform the same. User actual real world experience is going to be nearly identical.

On the other hand, if the ammo is 3 times as expensive to stock, you could buy a whole lot of other preps, or training, or pay down your mortgage, etc. with the savings - things you WILL notice a difference on.

10,000 rounds of 5.56 at .40 cents per round is going to be $4000.

10,000 rounds of an exotic at $1-2 per round is going to be $10,000-$20,000.

This makes the decision quite easy. I'd rather have the perfectly useful 5.56 and $6,000-$16,000 to prep in other areas where you will notice a difference.

Cheap IS tactical and useful.