How I chose a caliber for an AR rifle

[fastpat]

Rather than post in another thread, I figured this might be an opportunity, both for myself and others, to explain their decision making on this choice.

History: I spent about 30 years in the US government's military, first shooting an AR rifle in 1967. The details are somewhat fuzzy, except that I remember than it was an early one sans forward assist, that's what the Air Force purchased way back then. I also remember how easy it was to shoot accurately on the 100 yard range, despite the obvious wear these rifles had acquired as a basic training weapon.

Moving forward, I spent quite a bit of time on an M16 qualification range, courtesy of the four day Range Safety NCO course at Fort Bragg, and being designated range safety NCO for six years running in my Army National Guard unit during the 1980's and early 90's.

Details: I've always liked the form factor of the AR/M16, but that caliber was always a stopper for me personally. I don't want to turn this into a 5.56/7.62 discussion, but for me the 7.62 was the choice for anyone defending their home against a determined adversary. While I have an M14/M1A type rifle, my choice for actual use was the FAL. I built one for myself, and one each for my two brothers. That was that, I thought, I'd just have to tolerate the 12+ pounds of rifle. After considering a modernization of the M14, and seeing that it would weigh in at over 13 pounds, possibly over 14 pounds, I nixed that idea. Before acquiring the M14 and FAL, I had considered the AR10 from Armalite. The stopper there was price, compared to the FAL, and Armalite's notorious customer service, or lack of it, and the notion that you'd be stuck with modifying M14 magazines yourself, or buying the ridiculously expense Armalite units, to have a functional rifle. I passed on that.

Now: Then, a few years ago, I began reading about the new calibers available for the standard AR receiver. That interested me, so I kept an eye on development. I don't like the idea of being a beta tester for a life support device and that's what these rifles really are, so I waited for them to be developed further.

I weighed the two rounds that floated to the top, the 6.8 SPC and the 6.5 Grendel and decided this year on the latter. One reason, admittedly not a great one, is that the .270 caliber is historically a bastard 7mm bore cooked up by Winchester so that they could have a solidly proprietary cartridge and have a virtual monopoly on components. They accomplished that and it lasted for decades, pushed by the late Jack O'Connor of Outdoor Life Magazine. If it wasn't for O'Connor and Winchester, I dare say we'd not see any bullets between the 6.5mm and 7mm, but that's water under the bridge, well and truly.

My other, much more solid reasons, are that the 6.5 Grendel is still on the upward side of the development curve which means that it's going to continue to get better as time goes by. The bullets for this caliber are plentiful, ranging from light varmint bullets, to 140 grain low drag bullets. Hornady has developed a specific 123 grain bullet that they think is optimum for the 6.5 Grendel, at least for now. There are at least three other ammo manufacturers making ammo in 6.5 Grendel, so the shortage of resources has been answered I think. EDIT: I just ordered sufficient 6.5 Grendel magazines for the rifle at 11.99 each, they're C Products, the only source as far as I know, but that's pretty reasonable. That's the same price 5.56 NATO mags are.

The other thing that struck me was that the 6.5 Grendel varied between merely very good to simply outstanding at any range between the muzzle and 1100 yards. The 6.8 SPC was close, and quite interesting, but why go that route when there's the Grendel? I couldn't think of a reason. The rifles were the same cost wise, both took the usual AR accessories if one wants them, so my choice was made.

I should have this rifle built by the end of January.

Will I get rid of my 7.62NATO rifles? Nope, they have their place. But for a lightweight, easy to carry rifle, with 75% more muzzle energy than the 5.56NATO, the 6.5 Grendel has a lot going for it.

[Thomas M-4]

First off I respect your opinion and I my self have wanted to build a rifle chambered in 6.5 Grendel or 6.8 spc and when I first had the notion to build one I got tangled up in the 6.5 vs 6.8 debate then I came to realize the debate 6.5 vs 6.8 was hog wash both cartridges were designed to do two different things so what was the point of the debate
If I wanted to build a 16'' or shorter combat rifle it would be 6.8 SPCII chamber with ammo loaded to take full advantage of the spec II chamber 6.8 performs best with 16'' and shorter barrels Another reason I see reports that the 6.8 spc is easier to feed through a automatic action. Just the ticket for a compact rifle that packs the punch of a main battle rifle

The 6.5 is a accurate long range cartridge perfect for a SPR , style long range longer barreled rifle in the ar-15 platform.With the very high BC of the 6.5mm bullets the 6.5 will always be a top performer at long ranges.

[fastpat]

First off I respect your opinion and I my self have wanted to build a rifle chambered in 6.5 Grendel or 6.8 spc and when I first had the notion to build one I got tangled up in the 6.5 vs 6.8 debate then I came to realize the debate 6.5 vs 6.8 was hog wash both cartridges were designed to do two different things so what was the point of the debate
If I wanted to build a 16'' or shorter combat rifle it would be 6.8 SPCII chamber with ammo loaded to take full advantage of the spec II chamber 6.8 performs best with 16'' and shorter barrels Another reason I see reports that the 6.8 spc is easier to feed through a automatic action. Just the ticket for a compact rifle that packs the punch of a main battle rifle

The 6.5 is a accurate long range cartridge perfect for a SPR , style long range longer barreled rifle in the ar-15 platform.With the very high BC of the 6.5mm bullets the 6.5 will always be a top performer at long ranges.

Which type 6.8 SPC did you build or acquire?

[Thomas M-4]

Which type 6.8 SPC did you build or acquire?

My current plan is to start on it picking up parts first of next year.
Novoske 16'' barrel in 6.8 SPCII chamber
Mega upper and lower receiver
KAC URXII rifle length railed FF hand guard
Eventually I would like to top it off with a TA31H-68: 4x32 Trijicon ACOG optic.
Unfortunately this will be a long term project for me once I do start do to money being tight at this time.
I have already acquired reloading equipment which should allow me to be able to shoot it more once I do get it finished.

[Grendelizer]

the 6.5 will always be a top performer at long ranges.

The 6.5 Grendel also performs exceptionally at typical combat ranges of 0-300. To say that it's best reserved for long range is the equivalent of an urban myth.

John

[Thomas M-4]

The 6.5 Grendel also performs exceptionally at typical combat ranges of 0-300. To say that it's best reserved for long range is the equivalent of an urban myth.

John

Are you trying to bait me? I never said it did not perform from 0-300??

[tirod]

I'd like to suggest that when each cartridge was designed, one important criteria was whether it would have to function in a linked belt MG. 6.8, yes, 6.5, no.

That has nothing much to do with each rounds inherent application - which are different. It does have a lot to do with logistics and interoperability at the squad and platoon level. Honestly, not an issue to the average civilian shooter.

What does have an impact is the notion that a superior long range cartridge will be used that way. The whole point of the invention of the assault rifle is based on the researched and documented use of rifles in combat in short range engagements - not long range. The majority of kills by soldiers were within 400 yards or less. Add the higher rate of fire documented to put down more soldiers, and you get an intermediate round - not long range precision.

Basically, the higher BC effect isn't seen in combat, and is therefore a wasted resource when fielded to every soldier. When the range is needed, the .308 is in the system and used.

For the civilian shooter, again, much of that is moot - except for the actual use by them at long ranges. Some can and do, most don't shoot over 250 yards.

The average shooter will never consistently use the capability. It's like the pickup truck they drive daily to work, alone, with nothing in the bed. Wasted capacity.

That's the way staff studies saw the main battle rifle calibers, and the principles involved still apply to a choice between 6.8 or 6.5 - althought to a much more minor degree. Nonetheless, if long range is the goal, the 6.5 is the better choice - in that limited use.

Most would be well served with the 6.8, and that's part of the thinking I used in choosing it.

[Grendelizer]

I'd like to suggest that when each cartridge was designed, one important criteria was whether it would have to function in a linked belt MG. 6.8, yes, 6.5, no.

You have no evidence for this. Simply making it up?

The whole point of the invention of the assault rifle is based on the researched and documented use of rifles in combat in short range engagements - not long range.

If you've been following the latest developments, there is an ongoing effort to get weapons that hit harder at longer range. Thus, for example, the move to get M-14s back to the troops as a stop-gap measure.

Basically, the higher BC effect isn't seen in combat, and is therefore a wasted resource when fielded to every soldier. When the range is needed, the .308 is in the system and used.

Um, no. Military bullets use the highest BC they can, balanced by any competing factors. Witness the 7.62 147gr of M80 NATO.

For the civilian shooter, again, much of that is moot - except for the actual use by them at long ranges. Some can and do, most don't shoot over 250 yards.

Civilian 6.5 Grendel shooters have a wide variety of 6.5mm bullet options, including the option to "dumb down" the 6.5 Grendel with lower BC 6.5mm bullets if, for some reason, they want to match the ballistics of the 6.8 SPC.

The average shooter will never consistently use the capability. It's like the pickup truck they drive daily to work, alone, with nothing in the bed. Wasted capacity.

Your analogy is faulty. Military engagements vary, and it pays to be ready for anything. Better to have the capability (at no extra penalty) and not need it, than to need it and not have it.

Further, an assault rifle cartridge should be used not only in ARs, but also in machine guns and light sniper rigs, where you need to hit hard at long-range.

That's the way staff studies saw the main battle rifle calibers, and the principles involved still apply to a choice between 6.8 or 6.5 - althought to a much more minor degree. Nonetheless, if long range is the goal, the 6.5 is the better choice - in that limited use.

The top tier of our nation's special operations forces have downselected the 6.5 Grendel as their only choice, should they be authorized to develop and field an intermediate cartridge. We have this directly from their mouths. I don't know what "principals involved" you're referring to.

Most would be well served with the 6.8, and that's part of the thinking I used in choosing it.

This is true. Most civilians shooting paper or deer at 100 yards will be just fine with either one.

But because the 6.5 Grendel can do everything the 6.8 SPC can do, yet the 6.8 SPC cannot do everything the 6.5 Grendel can do, for military use, it's 6.8 SPC: Fail. 6.5 Grendel: Win.

John

[SHIVAN]

I am really growing tired of the internet debate on the 6.x's....

If this thread makes me regret posting here, knowing how it will go, I am probably going to lock some accounts.

So be forewarned that you guys can and will discuss this like mature, armed adults, at a friendly gathering.

Okay? Good.

[Cold]

Are you trying to bait me? I never said it did not perform from 0-300??

I dont think he was, he was just adding to the fact the 65 performs long and short.

I'd not want to be shot at short range with a 6.8 SPC or 65. Thats really the LONG and SHORT of it