6.8 SPC
.300 BLK
6.5 Grendel
5.56x45
7.62x40 WT
.50 Beowulf
.458 SOCOM

Vote for and discuss which round you feel is the best intermediate rifle round and why.

Why didn't you include the most popular intermediate round in the world, 7.62x39?

Just because I'm on AR-15.com and I don't know how many AR variants really run 7.62x39 as good as an AK.

Fair enough.  But just for the record, my Colt 6830 in 7.62x39 is a fantastic and accurate shooter.  

And the reason I would vote for the AK round is I can buy it cheap and stack it deep.

I voted 6.8. It makes the AR into a decent cover destroyer at 200 meters.

6.5 Grendel - Excellent performance at all ranges including really long ones.  Ammo for everyone from inexpensive Wolf with pretty good accuracy (1.5 moa for me), to some seriously accurate factory ammo (Lapua Scenar), to excellent hunting ammo for animals up to elk-size.  If Wolf ever gets the steel-case stuff here, it will even cheaper to practice with.  Probably the best all-purpose intermediate cartridge ever made.

Four of those are not intermediate rifle rounds....

6.8 or 6.5 hands down, either offer the most performance from a AR15.

Yes.



And although I prefer 6.5 over 6.8, I think that 6.8spc is best suited to most shooters' needs.

I don't consider the SOCOM or the BEO to be "intermediate" rifle rounds, bu then I don't know what you had in mind for the upper tier.

It's a three way toss-up from the choices offered:


6.5mm Grendel for longer distances.

6.8mm SPC II for overall performance.

7.62x40mm for close to mid-range distances &
high performance on larger animals and a better
overall performance than than the x39mm.

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For the big bores the advantage goes to the .458 SOCOM
due to the market share and general acceptablility/availability
for the AR-15 platform.

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Happy/Healthy Easter to all.

6.5 Grendel.

It does everything all of the others do up close then keeps striding along.  From a "One cartridge do it all" standpoint the 6.5 wins hands down.

The 6.8 has a bit of an energy gain on it within 300 yd, but IMO it's about negligible in the real world, both have taken many medium and large game animals at ranges most wouldn't think to shoot them at with a .30-06.

6.5 Grendel over the 6.8 by a thin but real margin due to its availability to go long.

They are essentially equals out to 3-400 yards where the Grendel begins to have an advantage.

Beo and .458 as intermediate rounds? Whats a big bore, then?

The 5.56 and .7.62 don't qualify as intermediates in my book.

6.8 or 6.5G

   RJ

Depends what you plan on using it for really. Most of these rounds were made for a specific purpose in mind.

If you need something to shoot through body armor but not through walls then 5.56mm is the best. It's also accurate and has good range. It's also lighter to carry more ammo. It's the best choice for a military round I think. The only thing I don't like about it is the fact it can't shoot through barriers to a target very well. Then a heavier 7.62mm round is better for that.

6.8 SPC is an interesting round and good for hunting I hear. But I don't like how expensive the ammo and special parts are.

The 6.5 Grendel was made for long range shooting and it's very good for that. If I was a long range target shooter I would get this round. But I prefer my bolt action rifles for that.

The 300BLK is very quiet with subsonic ammo and a suppressor. No need for hearing protection at all, it's hearing safe. it can also use supersonic ammo if you want a little more range or punch out of it. So it's a versatile caliber and I really like that it uses standard parts and mags.

The 7.62x40mm packs a little more punch than 300BLK supersonic ammo. Still uses standard parts like the 300BLK, but the mags need a little modification.

I don't know much about the .50 or .458 except that they are big and good for hunting. It's not my cup of tea though.

I have both 5.56mm and 300BLK and suppressors for both. I have most my bases covered with these two rounds and I don't feel a need to get any other caliber. I really like that the only difference is the barrel and everything else is the same. So as far as spare parts and mags go i'm set. And if i need more power I will just step up to a full power rifle round like the 7.62x51mm. That's my thoughts though.

I could be wrong but it seems the only definition I can find for an "intermediate rifle round" is something that isn't as powerful/long range capable as a full-house rifle round like a .308 or .30-06 (and above) but it is superior in power/range/accuracy to a pistol caliber carbine. So, correct me if I'm wrong, but all of these guys should apply.

Just my opinion, but I think the 308 is the best intermediate round.  To me, high power means 338 Lapua, or 50 BMG, but my tastes tend to be extreme!!!

Doc

6.5 Grendel offers the widest spread of capabilities.

Load it light with varmint-weight bullets in the 85gr-95gr range, and run high velocities for short-range, low-recoil devastation.

Load it with 100-120gr projectiles for medium game hunting.

123gr Target bullets with .510+ BC's at 2500+ fps makes a great 600yd+ AR.

Use the 130gr class hunting bullets for heavier game.

.308 isn't an intermediate round by any means.  It's the 1950's version of a battle rifle chambering, packed into a shorter case, with similar recoil and external ballistics.

The 7.92x33 is generally accepted as the first true intermediate cartridge.

The 6.5 Grendel and 6.8 SPC have ushered in a new era of high-performance intermediate rifle cartridges, roughly duplicating the capabilities of the .276 Pedersen and .280 Enfield, but from smaller cases and the AR15 action.  This is a big plus for hunters and target-shooters who don't want the weight and recoil penalties of the .308-based cases.

.300 BLK because it is easy to load subsonic.

mbogo

"Best" at what?

300BLK marketing machine still working overtime HERE...

6.5 or 6.8––-I chose the 6.8 because it has proven very effective in taking game for me.

I voted 6.5 for range, accuracy and retained energy beyond 300 yards. And I have one.

I've got to agree with docGP.  The .308 is a good intermediate round.  It is a very watered down compared with the 30-06 unless one
is shooting very light bullets.  Any cartridge case that holds only 25 or 30gr of powder is hardly an "intermediate rifle round".

The .308 was never designed nor intended as an intermediate round. It was designed as a 30-06 equivalent from a case designed for a shorter action. It was intended as a Battle rifle round, with the hope of 30-06 performance from a shorter case. As such, it has comparable ballistics and recoil.

The 6.8 and 6.5 Grendel deliver performance significantly greater than the first intermediate cartridges, and bring it to the AR 15 chassis.

I stand corrected, (thanks Stan) and have corrected my response.

By the original definition, 5.56 and 7.62x39 qualify, but to me are outmoded.

As originally conceived, an "intermediate" rifle cartridge is significantly more powerful than a service pistol round, but significantly less powerful than a standard (full-power) rifle cartridge. Power, not bullet diameter, determined classification.

It happens that the first, purpose-designed, intermediate rounds had bullets of the same caliber as a country's full-power rifle cartridge:

7.62x33 / 7.62x63 - United States (.30 Carbine / .30-06)
7.92x33 / 7.92x57 - Germany
7.62x39 / 7.62x54 - Russia

.300 BLK, 7.62x40 WT, 7.62x39, and 5.56x45 clearly meet that definition.

.458 SOCOM and .50 Beowulf are special-purpose rounds, not general-purpose assault rifle cartridges, which kinda muddies the water.

I'm not sure why people hate on the 300BLK "marketing machine".  The strong marketing for the round does nothing but good things for us as shooters.  It increases the number of weapons chambered in 300BLK, it increases the number of companies selling 300BLK ammo and lowers the cost for us all.  I for one didn't touch it until after over a year of it being on the market because I was waiting to see how well it would "catch" and it seems to have "caught".

I would love to have and will probably build a grendel at some point but one thing that really pulled me towards 300BLK was the ability to use surplus 30 caliber bullets in reloading for it.  The ability to use all those neat and varied (and inexpensive) surplus bullets is a really great feature of 300BLK.  In addition, like has already been mentioned I can use all my 5.56/223 parts other then the barrel which really helps to lower the overall cost.

You really have to look at how your going to be using it.  If your doing lots of long range shooting then 6.5 Grendel seems the obvious choice.  If, like most of us, you only shoot paper or steel then arguing over Ft/lbs is really kind of goofy and mallninja-ish (but I can't say I haven't fallen into that rut more then once. lol).   If your hunting then .27-.30 caliber has killed plenty of critters, so really any of them should work great given proper shot placement.

In the end I got 300BLK for what I consider the most obvious reason, it is absolutely wonderful suppressed and pretty inexpensive and easy to load for.  If your setup for loading 5.56 and 308 then your basically setup for loading 300BLK.

The problem is the OP asked for the best––-not which one you could afford or which one you would like to have cheaper components for. And I was just pointing out to the OP and other interested parties that the poll results were going to be skewed.

In the end the best is found somewhere between 6.8 and 6.5––-you even seem to agree with this in your post despite your attempt to defend the 300BLK marketing BS.

Right now I am going to say 6.8, but after next weekend I may change my mind.

Going to try out my new 300 Blk when the barrel gets here.  

He asked what the best was, not the most powerful or the one with the highest BC.  Just like if I asked what the best motor vehicle was someone could say Ferrari 458 and the next guy could say a humvee and they would both be "right".  In many peoples minds "best" isn't most powerful, or flattest shooting.  Maybe best to some people is most available, cheapest, or best suppression. Or maybe its a combination of long range performance and cost (which would be the 6.5 grendel at this point).

Obviously you have some beef with AAC or Robert but I'm not sure why that makes the round BS, or the (excellent) marketing for it to be BS.  It was great as the 300whisper, now you get 300whisper and 300fireball out of the same gun without the need of an adjustable gas block or other "tweaks" to keep it running.

Regardless, OP asked "best", not "most powerful, highest BC" and in this case best to me is 300BLK for the reasons I laid out.  Its also interesting to note I'm not the only one that believes the same thing.  A quick look at midway shows 4 of the top 5 most popular loaded ammo they sell is 300BLK.  I consider that an excellent thing for those of us who have invested in the caliber.  I wish for a long healthy life for the cartridge.

Sometimes people forget that they took the best girl to the dance.

I think that the 5.56x45 NATO is the best intermediate rifle round.  FIrst, is low recoil, allowing for light weight arms that the easy to carry. In addition, the low recoil makes for quick accurate follow up shots. Second, the light projectile (62 gr) can be pushed to 3000-to-3,100 ft/s (in 20 in barrels and about 2800-to-29–– ft/s in 14.5 inch barrels). This makes for a flat trajectory out to about 300 meters. Third, all this in a light cartridge so that one can carry more ammo.  In fact, one can carry more than twice as much 5.56×45mm ammunition as 7.62×51mm for the same weight.

As far as lethality goes, lethality of the 5.56×45mm was more a matter of perception than fact.  A good CNS hit with any cartridge will result in quick/instant incapacitation. Similarly, a poor hit with any cartridge yields poor incapacitation results. Most of the complaints about terminal performance have more to do with the bullet construction than the cartridge. It is much cheaper and simpler to fix the bullet design than change calibers.

Copying is the best form of flattery

The 5.56x45mm has proven to be so effective in its all around performance, it has been copied by both the Russians and Chinese. The 5.56x45mm came out in 1963, by 1974, the Russians abandoned the 7.62x40mm and adopted the 5.45×39mm. About 13 years later, the Chinese also abandon the 7.62x40mm and adopt the 5.8×42mm. Both of these rounds are ballistically similar to the 5.56x45.

This why I believe that the 5.56x45 NATO is the best intermediate rifle round.

Bullet wt./Type                  Velocity                Energy

5.56x45mm 

4 g (62 gr) SS109 FMJBT   940 m/s (3,100 ft/s)     1,767 J (1,303 ft·lbf) *

5.45×39mm

3.68 g (56.8 gr) 7N22 AP  890 m/s (2,900 ft/s)     1,457 J (1,075 ft·lbf)**

5.8×42mm

4.15 g (64.0 gr) FMJ      950 m/s (3,100 ft/s)     1,795 J (1,324 ft·lbf)*

* ~ 20 inch barrel
**~16 inch barrel

after having shot a buddies 6.5 grendel out to 400+ yards I am sold. I would agree completely.



 

Poll should specify the purpose of the cartridge selection.  6.8 or Grendel is not what I would want to shoot in a confined space even with a suppressor.

If the purpose is to use for cqb and still be able to do some quiet hunting the 300 BLK is the ticket.

If to provide a good hunting round for medium game up to 300 yards the 6.8 has real merit.

If to be used at more than 400 yards, the higb BC of 6.5 projectiles suggests the Grendel.

If I wanted to whack black bear I might well consider the .458 SOCOM.

Personally I have ARs in 300 BLK and 6.8.  I have bolt rifles in 264 Win Mag, .338 Win Mag, .375 H&H, .416 RIgby and .458 AccRel for work at range and for things that bite back.

6.8 spc spec II for my vote.  300 blk is best at subsonic and thus becomes a close in rifle and not an intermediate.  I like the grendel and almost bought one but I can easily get ammo for the 6.8 at the time and all my buddies now have a 6.8 and it kills deer/hogs with extreme prejudice!    I have a Socom and would not consider that or the beowulf to be intermediate rounds.  They are not but are fantastic close range firearms.

I picked 300BLK because of all those listed, it seems to be the most versatile. From heavy-hitting subs to near-7.62x39 performance super, it can do both well. It's not as flat shooting as a 6.5 or 6.8 to distance but with a simple mag change and a silencer you've got essentially the best of both worlds for any situation you will probably encounter, without having to tweak or adjust anything. The benefit of using the exact same parts as a 5.56 save the barrel makes it easy to switch between calibers if necessary, as mags and bolts are caliber neutral. Does it have the long range performance that a 6.5 or 6.8 has? No, but I also don't have to have any dedicated parts. Now using the same bolt isn't the greatest idea, but in austere situations the ability is beneficial.

All of the calibers listed tend to do one thing well, but have their drawbacks or set of quirks. I think generally speaking, the 300BLK has the most benefits with the least amount of compromises. Master of none, but without the compromises that go along with the others listed.

While 5.56 is a great choice in its own right, I look at this discussion more as a comparison to that being standard, rather than inclusive with the rest of the choices.

+1 on this....

Not to throw another log on this fire, but the difference between the 6.8 and 6.5 out to 400 yards is so minor that most shooters will never be able to see the difference.  Definitely out to 400 you won't see jack for difference.  The Grendel (at this time) definitely has an advantage from 600 onward, however....

The .308 is NOT an intermediate rifle cartridge.  It is a battle rifle cartridge, basically duplicating the performance of the older M1 .30 cal service rilfe cartridge from the 1903 Springfield and the M1 Garand, but in a smaller, high-pressure case.

The intermdeiate rifle cartridge was introduced by the Germans in the Sturmgewehr, with the 7.92x33.

Intermediate rifle cartridges are meant to bridge the gap between a Submachinegun and a battle rifle, taking the mag capacity of an SMG, with the practical effective range of a battle rifle out to 300m.

As such, the Beowulf, .458 SOCOM, and heavy loads from the .300 BLK don't qualify as intermediate rifle cartridges.

The 300 BLK only makes the mark if you load it light and fast.

While the Grendel and 6.8 have very similar trajectories out to 350yds, the Grendel has a clear advantage along that entire flight path once the terminal ballistics kicks in for penetration on game, and can still download to the lighter bullets in 85gr-95gr weights running fast-still with better sectional density.

5.56 NATO is still the best intermediate cartridge from a military perspective for a ton of reasons, but the Grendel offers the most versatility across the performance envelope between hunting and military use, as well as a whole new concept that hasn't been fielded yet.  I'm a first-hand witness of 5.56 performance on human tissue many times, and I can say that within 150m, it was devastating in every one of my admittedly anecdotal experiences.

this could be debated forever, each person gets like it is ford vs chevy vs dodge...

what it really comes down to what you are using it for.  I looked at the poll, has the 300 Blackout rated the highest so far, that is crazy, of course the link to this thread is on the 300 BLK website, so thats why the numbers are higher.  So the question is, which you didn't specify, are you going to use it suppressed part of the time, all the time or not at all?

assuming you are going to use it suppressed most of the time, then it would be either the 300 Blackout, or the 6.8 BSP.

next, if you are not going to use it suppressed and shoot it supersonic some or all of the time, then two options, the 6.8 or 6.5G or .264 LBC out of the ones you specified.  

I seen a post recently that the 300 BLK was designed to be used subsonic/suppressed, in a sense that is true, however was also designed to be used supersonic suppressed or unsuppressed and it will shoot lighter bullets supersonic either suppressed or unsuppressed.

But if you have no plan to shoot subsonic suppressed part of little of the time, better going with a cartridge that is the best performance, that would leave it at the 6.8 or 6.5G/.264LBC, they just offer more range.

Then it comes in to play, do you plan to reload?  If not and shooting supersonic, the 6.8 offers more factory loads than the 6.5G/.264.  However if you are reloading, they 6.5G/.264 offers alot of bullets for both match shooting and hunting as well as the 6.8.

As far as the big bores, well, you didn't specify what distances you are going to shot.  The 458 SOCOM, 450 Bushmaster and 50 Beowulf are good cartridges for 200 yards or less, i've seen people shoot them further, however I would limit the range due to the speed and trajectory of these rounds, but great knockdown power on all of them.

So, what is it?  Subsonic, Supersonice, Suppressed, Unsuppressed, 200 yards and under, over 200 yards, over 300 yards, reloading, not reloading, animal type (hogs, deer, antelope, elk, moose, etc.)????

7 x 46

As others have noted, "best" is subjective. Since we're talking assault rifle cartridges, I vote for .300 BLK, for:

- Flexibility of supersonic loads for general use, and action-cycling subsonic loads for suppressed.

- Adequate terminal performance w/supersonic loads, without sacrificing 5.56x45 magazine capacity.

Plus, I'm from the .30-caliber generation. My all-time favorite long guns were my M1AE2 rifle and M1 carbine.

I would disagree with the assessment that the 300 BLK is not an intermediate round.

I consider 0-50 Meters to be carbine sub-cal distance,  then out to 300 Meters as the intermediate distance, and beyond 300 Meters to be long distance.  The U.S. Army Rifle Marksmanship Course extends from 50 to 300 meters so that is a standardized benchmark of what I would consider to be an Intermediate Cartridge.    

Where the 6.5, 6.8 and 30 AR have a velocity and drop advantage in the long distance overlap beyond 300 Meters, the 300 BLK is superior in the carbine sub-cal distance overlap especially out of a 10" barrel with suppressor (think weight, sound and maneuverability).

IMO, long distance capabilities are not the sole factor when choosing an Intermediate caliber as it contradicts the definition of the caliber.

I thought the OP added the 300 as a joke. If we are going to pick a weak round, the 5.56 would be the best choice. It offers velocity, reach, a decent trajectory and is cheap. The FMJ and AP type bullets are what gives the 5.56 a bad rep, use a 64gr+ SP or OTM bullet and it would be much better.

Bullet technology allows the 556 to do anything that the others can.

Where is the 545 option too?

I voted for 300 blk.  Why cause I just looked up the 6.5 and 6.8 on Hogdgon Web page and I don't see any 130 gr plus loadings?  And someone posted above all the bullets the 6.5/6,8 are supposed to use but yet theres no loading for it.   And from what I see at the load site  there isn't that much difference in the FPS  between them and the 300 blk. And yet the 300blk can and does shoot every 308 caliber bullets out there.   And if you look at the 6.5 and 6.8 they really get slow with anything over 120 gr  - 300 blk can an does push the 130gr  at 2300 fps   what the 6.5/6.8 do with a 130 gr?  What can the 6.5/6.8 do with 150 gr? Oh thats right they don't have one.

You are going with the same basis most 300wtf koolaid drinkers go by. Since it shoots a .30cal bullet, must be the best? Wrong, except for the lighter bullets, which have less ass than a 7.62X39. When you move up to a real .30cal bullet, such as a 168gr, the 300 lobs it like a mortar, with no authority. The 300 will never be anymore than it is due to the 5.56 case. Why do you think the 6.8, 6.5, 7.62X40 type cartridges were devolped? You got to have that extra room in the case to get some more power.

I will agree the 300 makes for a awesome SBR shooting subs suppressed but then again the 6.8BSP kicks its ass too.

Moral of the story, the 300wtf doesn't compare to anything other than the 7.62X39 and even that round has more power.

two or more are missing aren't they?

Just to clarify...  When I see the word "intermediate" I'm thinking "in between."  When talking about AR-type weapons, to me that means in between the 5.56 and the .308.  I'm a big 6.5 Grendel fan, but I think the best intermediate cartridge would have to be the .300 Blackout.  The Grendel and the SPC are trying to be a .308 in a AR15 receiver.  That's not the goal of the Blackout.  It gives "intermediate" 7.62x39 performance in an AR15 platform, and it does this using the same mags and bolts.  Being able to easily suppress it is just gravy!  (You'll note in the literature that the suppressed Blackout is compared to the HK MP5SD, not a suppressed M4.)

I guess the first decision you need to make is, "What range are you most likely going to use this weapon at?"  I know that this is totally subjective, and many may disagree with me, but I believe a logical breakdown would be as follows:

0-200yds .300 Blackout SBR
50-400yds 6.8 SPC 16" carbine
200-600yds 6.5 Grendel 18" rifle
200-800yds .308 Winchester 18" rifle

I live on 3.5 acres of forest land, most of it rather steep.  For me the best choice is my 9" Blackout.  It's light and handy, and there's no place on my land that I can make more than a 150 yard line-of-sight shot.  A 5.56 would probably work just as well for the coyotes, skunks, raccoons, etc., but we also have mountain lions and I'm just not confident in the smaller, lighter .22 caliber bullets.

346ci
So running a 150gr bullet at 1900 plus fps is lobbing a mortar?  I bet theres alot of 30-30 guys that would slap you around for that comment.   Not to mention the millions of deer/ bear that have died from those mortar shells from a 30-30.   So show me the data of the 6.5/6.8 with 130 gr and above? My 300 throws a 125 gr at 2185 fps  as I said I don't see no data for the 6.5/68 . By looking at the heaviest ones they do shoot they don't have much on the 300 Blk .   And this300 Blk data is on a 16" barrel- don't most of you 6.5/6.8 guys shoot a 20" or longer barrel?   Do you have data based on 16" barrel as I know Hogdgon data is on a 20 " barrel for 6.5/6.8  so we need to take atleast 100 fps of the data shown below!

6.5 G
123 GR. SIE HPBT  Hodgdon  H335  .264"  2.250"  26.0  2288  37,800 PSI  28.7  2508  49,800 PSI        
123 GR. SIE HPBT  IMR  IMR 8208 XBR  .264"  2.250"  25.5  2180  33,900 PSI  28.5C  2497  50,000 PSI        
123 GR. SIE HPBT  Hodgdon  Benchmark  .264"  2.250"  25.0  2225  36,900 PSI  27.5C  2460  49,900 PSI        
123 GR. SIE HPBT  Hodgdon  H322  .264"  2.250"  24.0  2192  36,600 PSI  26.6C  2434  49,900 PSI        
123 GR. SIE HPBT  IMR  IMR 4198  .264"  2.250"  22.0  2263  43,300 PSI  24.2C  2385  50,500 PSI        
123 GR. SIE HPBT  Hodgdon  H4198  .264"  2.250"  21.0  2153  37,700 PSI  23.7C  2375  50,000 PSI  

6.8

115 GR. SIE HPBT  Hodgdon  H335  .277"  2.260"  27.0  2415  40,800 PSI  29.0  2569  48,500 PSI        
115 GR. SIE HPBT  Hodgdon  H4895  .277"  2.260"  27.0  2302  34,300 PSI  29.0C  2495  42,800 PSI        
115 GR. SIE HPBT  IMR  IMR 8208 XBR  .277"  2.260"  28.0  2483  41,800 PSI  30.0C  2647  51,400 PSI        
115 GR. SIE HPBT  Hodgdon  Benchmark  .277"  2.260"  26.0  2400  42,400 PSI  28.5C  2581  51,800 PSI        
115 GR. SIE HPBT  Hodgdon  H322  .277"  2.260"  26.0  2421  43,500 PSI  28.2C  2608  53,300 PSI        
115 GR. SIE HPBT  IMR  IMR 4198  .277"  2.260"  22.0  2386  43,100 PSI  23.5C  2515  50,000 PSI        
115 GR. SIE HPBT  Hodgdon  H4198  .277"  2.260"  22.0  2413  47,800 PSI  24.0C  2534  52,300 PSI  

300 Blk


125 GR. NOS BT  IMR  IMR 4227  .308"  2.060"  16.5  1818  38,000 CUP  17.7C  1965  49,800 CUP        
125 GR. NOS BT  Winchester  296  .308"  2.060"  16.7  2020  40,200 CUP  17.8  2118  48,800 CUP        
125 GR. NOS BT  Hodgdon  H110  .308"  2.060"  16.7  2020  40,200 CUP  17.8  2118  48,800 CUP        
125 GR. NOS BT  Hodgdon  Lil'Gun  .308"  2.060"  16.9  2086  35,900 CUP  18.0  2185  40,800 CUP  

Most of us use a 20" bbl? LOL We run a majority of 16", some 18s and 20s, very few 20" rigs out there. The 6.8 doesn't need that extra length to gain velocity such as a 5.56, it preforms like a raped ape from a 16".

Your 6.8 loads are what a dinosaur would use, the SAMMI stuff is dead. Try a 110gr going 2700+ FPS, from Wilson Combat, a FACTORY load, out of a 16" bbl.

I'll tell you what. I will make it fair and leave the 6.8 and 6.5 out of this. Show me why the 300 is a better choice over a 75gr 5.56. And I will let you use those duds of a 125gr. load you just posted.