Please school me here, I'm a blank slate

AR/M4 Beyond 5.56/.223
1

Hey guys!

I’ve been toying with the idea of a third AR platform. My other two are built following the general guidelines this site likes, which works great for self defense and general purpose uses. I had been working up an idea for a precision rig when I thought about going to an alternate caliber that may do things better.

So, since there are so many alternate choices out there, I don’t know what may work best for my purpose. I thought the 6.8 would be great, but have read that it was designed for shorter guns. The Grendel looks like another option, but I just don’t know much about it.

That said, here are my requirements…

I want to build this into a full length rifle. Fixed stock, barrel between 18" and 22" with a preference for the middle ground. I would like to keep it within the AR-15 platform for weight and parts commonality sake, but I am willing to step up to the AR-10 if absolutely necessary. Weight is a concern, but not a huge one (not MTU contours). I am leaning towards a DMR/SPR type setup.

The primary goal is accuracy. But beyond that, I want it to work well for both paper punching and pinging steel out to 1000 yards (the furthest my local range has). I would like it to be a capable hunter out to 400-600 yards.

Besides my two ARs, I also have a scoped M1A, a M1 Garand, and a 20" .308 bolt gun. Some overlap in capability is fine, but I’m trying to fill a different niche I guess.

I’ve long heard about the absurd BCs of the 6.5 family (I’ve been heavily eyeing a 6.5x55 or .260 bolt gun build), but I am interested in the semi-auto route and what other options that opens up.

I plan to entering the world of reloading before the end of the year, if that makes a difference.

Any advice? Should I stick with the 5.56 platform or just go to the .308 AR route?

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6.5 Grendel in the -15 family or 6.5 Creedmore and .260 in the -10 family.

If you go the way of the .308 receiver, you start getting into the area where the longer barrel you want will help. On a lot of the shorter rounds a long barrel really does not give you a significant advantage.

The one big thing I would check first is the availability of match ammo. See what Black Hills, Nosler, and a few others make. If you don’t reload right now, this might take a few off the table right away.

3

I personally don’t think any of the intermediate cartridges that fit the AR15 platform are adequate for hunting out to 600 yards. Unless you are talking coyotes or other varmints. But for deer sized game they all come up lacking at that range…400 yards is stretching any of them to the limits when you take bullet construction, velocity and KE into account.

That said both the 6.8 and 6.5 are great cartridges with alot of overlap in performance capability. The 6.5 has a much better selection of long range target bullets, while the 6.8 has a much better selection of expanding hunting bullets. I see the ethical hunting ranges between the two to be about the same 300-350 yards.

I say build both:D

I have 3 more wildcat uppers I want to build off the 6.8 case… 22/6mm/ and 30 cal…currently playing with a 358 wildcat on the 6.8 case. 200gr @ 2100-2200fps fun stuff!!
Then I plan to start playing with the Grendel and wildcats based on the x39 case.

Reloading is quite the addictive hobby. Combine that with a bad case of BRD and things get expensive quick!!

4

Thanks for the input.

I’ll clarify that the hunting would most likely be against Coyote or other smallish game. If I was planning on something larger, I would go up to my .308s or 30-06. Not that I would take a shot at 600 yards anyway (ethical reasons due to my current skill level), but having the capability is nice.

The availability of match ammo is something I understand is important, but this project is going to quite a ways away. My wife has offered to buy a new lower now, before we get PCSd to California, for some future project. I am just trying to weigh the options. By the time I actually start building, I expect to be well into reloading.

More than likely, the primary role of the gun is going to be target shooting. 1000 is probably excessive for the -15 platform, so I’ll reduce that to 600-800 with a capable hunting range on smallish game of 500 yards.

Again, though, this comes back to the question of capability. Does the 6.5 or 6.8 offer enough of a boost in performance over the 5.56 to warrant the smaller selection of parts?

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Gotcha. Then I would go 6.5 Grendel personally. I think it does have a boost in performance especially at the distances you are talking about.

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Since you already have a semi .308, 30.06, and a bolt .308, I would say don’t go the route of an AR10. The 6.5 Creedmore is an excellent round that will be able to get to 1000 pretty easily, and Hornady makes a good match 6.5CM that can be had for about 25/box of 20. Other rounds like the 6.5 Lapua or the .260 rem will get the job done to 1000 but the ammo is pricier. I will admit, I don’t know crap about the 6.5x55 Swede. I know Prvi makes a match ammo for it that can be found for about 17/box, but I don’t know of its long range capabilities.

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I have been doing a lot more reading and comparison of ballistic charts.

The one in the OP here compares the 77 gr OTMs I shoot now to 7.62, 6.8, and a few flavors of 6.5.

It would appear that from a 24" barrel, the 6.5 meets my requirements almost exactly. The 123gr Lapua load stays supersonic out to 1300. Cutting a few inches off the barrel still keeps me right in my sweet spot.

Romeo, the 6.5x55 Swede is what got me interested in 6.5s to begin with. My understanding is that modern factory loads are actually underpowered due to high probability that they will be shot from an old Mauser instead of a modern strong action. Guys hand loading them are getting great performance on par with the 6.5x284, but without the barrel burning characteristics. I had been toying with the idea of another bolt gun in either the Swede or 30-06 pumped up to near .300 WM velocities.

Thanks for the input, all. Another question, though. Does using the 6.5 or 6.8 varieties require different buffer components? Or would a standard rifle buffer and spring work just fine? I understand there will be a bolt change, but that’s no big deal.

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Since long range shooting seems to be your primary goal, The 6.5 with a longer 20-24" barrel will get you there.

I can;t speak to much about the function of 6.5’s as i don’t have one. But with the 6.8 a standard carbine buffer seems to work just fine for most people with a mid length gas system. Some guys will run a stiffer spring and heavier buffer to aide in cycling with hot hand loads. Sometimes it’s not needed. I believe the variables mostly come from different gas port sizes and locations ( rifle vs mid etc)

I am currently waiting on a 22" 6.8 barrel to build a target rifle. Shear curiosity got the best of me. I want to see if I can push the 140gr Berger VLD’s to around 2600fps. Will be fun to see what the end results are. I think I should be able to get very close to that # based on a fellow Aaskans testing with a 24" barrel. He is pushing 110gr accubonds over 3000 fps…Which is pretty damn impressive in my book.

If I wasn;t already so vested into 6.8 parts and reloading components, I likely would have just done this build as a 6.5…:smiley:

One thing to be aware of with the 6.5’s The Grendel and LBC have different head space. So bolts are not interchangeable between the two. If I remember correctly the x39 bolts will not headspace properly in a Grendel either. Not a huge deal, just something to be aware of before you start. I am sure one of the Grendel guys on here can elaborate on this issue and/or correct me if I am mistaken.

Good luck on your project… Sounds like a fun build.

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A few comments:

  1. Unless you reload, stick to the .308 and 5.56 due to ammo availability and pricing.

  2. If this gun is for targets, not men, then the 5.56 will be fine out to 600 yards.

  3. Out to 600 yards the 6.5 cartridges do not offer all that much over the .308. It takes longer range for the 6.5s to come into their own.

  4. M1As tend to break some time after 500 rounds. The reason an M1A costs $1200 and a proper milspec M14 (like from Fulton Armory) costs $2800 is because quality parts cost more. If you M1A is a plinker, then fine. If you intend to risk your life based on performance of the M1A, I would suggest you ditch it and order a proper milspec M14. Instead of spending money on a new AR, you could use those funds to upgrade to an M14.

Personally I feel a constant sense of irritation when there is a rifle in my safe that is not combat quality. I used to own 5 x M1As. But then they started crapping out on me. I researched them and found out why. So I do not own M1As any more.

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I’m not sure you read the whole thread. This build is a ways a way, and I will be reloading by the time it starts.

It’s primary role is target and silhouette shooting out to 1000. But, frankly, I’m not a fan of a single use gun and like the possibility of any of my guns being pushed into “social” use if required and being quite capable. As far as the M1A goes, it was my first rifle and it has undergone significant modification for both reliability and accuracy. Very few parts remain factory, and after I have Smith Enterprises mount a new barrel at some point in the next year, the only remaining stock part will be the trigger and receiver. To date, the rifle has seen thousands of rounds and has suffered no malfunction that was not related to poor ammunition.

AK_Hunter, thanks for the advice. When I actually get around to doing this one, I really do think it’s going to be a kick ass build.

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My personal view is for top long range work in a AR-15 platform the
6.5mm BRX gets the call.

For the AR-10/LR-308 platform, the .260 Remington gets the call.

YMMV.

12

You already have two 5.56 mm rifles, two .308 rifles, and a .30-06.

5.56 mm will punch paper out to 1000; .308 or .30-06 will take care of all your hunting needs.

Why add another caliber?

If you really want to go long, not just for target shooting, but also hunting, consider a hot loaded .30-06 bolt gun. If you want to get a bit more umph, how about a .300 Win Mag bolt gun shooting 220 gr loads.

If you are serious about shooting farther, but want a semi-auto, the .260 Rem and 6.5 Creedmore are FAR more capable long range cartridges than any assault rifle based caliber that fits into an AR15.

Personally, since a 16" .308 LaRue will handle 90% of my shooting needs, I don’t really need much in the way of other rifles anymore. However, until my supply of free 5.56 mm drys up, I feel compelled to keep shooting my AR15’s due to economic reasons…

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Why not add another caliber? Not all guns need to be for “duty” use. Or share common ammo. Just because a cartridge doesn’t make sense for widespread LEO use does not mean it has no place at all for enthusiasts. Sometimes playing with other calibers is just fun. Pure enjoyment is reason enough for me.

Dr69er makes a great suggestion though. The 6.5 BRX is by far the hottest of any of the 6.5 variants that will fit into an AR. That said it also requires the most work to reload. Fire forming your brass is needed to see the full potential of the cartridge. Not a huge deal for a casual shooter though.

I just saw Hornady is releasing a 123gr SST. Specifically designed for Grendel velocities. That is a very good thing in my book. I do believe that is the first hunting bullet specifically designed for the Grendel. It will very likely increase the range of it’s terminal performance.

Brigand have fun with your project. If it makes you smile when all is said and done…then it was money well spent.:smiley:

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Note that that link dates to February 2004. I took a quick look and the advertised velocities in that chart are much higher than most people are getting with 6.8 SPC and 6.5 G (I realize that most people are using 16-18" barrels for 6.8 and 16-20" barrels for 6.5 G, but neither one has lots of powder capacity so they don’t get as much velocity gain in long barrels as .223 / 5.56 or magnum and high velocity varmint cartridges). The only set of data that looks completely realistic is the .308.

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I agree with you Doc. I don’t get much free .223 ammo from my job, but I get access to several thousand once fired .223 brass cases a year for reloading. This means that I spend only about $.12 a shot for my cheap .223 range ammo, and about $.20 a shot for my match grade/hunting/defense ammo. So, I end up shooting through around 10k a year in .223 and I have money left over for going to shooting classes, and purchasing other equipment such as optics, mags, range finders,…etc. I also get a small supply of .308 brass, and if that supply were to increase I would justify converting to it.

Although I would love to get into another caliber such as the 6.8 or 6.5, the cost handicap would be incredible in the long run if I were to train with the calibers. I did all the cost calcutions for purchasing reloading components for the 6.8 or 6.5, and the cost would force me to cut back on my annual round count in 5.56 quite a bit. If I were to shoot only 6.8 or 6.5 in place of 5.56, the annual cost would be about 70% greater…meaning only 3k rounds per year on the same amount of money since I have no access to free casings. Now from a reloading standpoint, there is very little cost difference between the .223 and 6.8/6.5 if you have no access to free empty cases. So, if you want to dedicate yourself to running one of those calibers it isn’t so bad. However, you do occasionally run into other complications for those odd-ball calibers such as the need for specialized case trimmers which add additional costs.

However, running multiple calibers even if you reload DOES get expensive. Each system needs its own support such as multiple rifles/uppers, optics, magazines, cleaning gear, different reloading components and tools…etc.

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Doc, thanks for that. The question of adding another caliber was exactly what brought me to post here.

Up until this project got into my mind, I was indeed planning on a 30-06 bolt gun for getting way out there. That way, for reloading, I consolidate enough calibers to not have to mess with a lot of variety in equipment.

Honestly, what drew me to this project was limitations with my M1A. As reliable as it has been, it has limitations. It’s heavy, 17 pounds with the JAE chassis and scope, and the M14 is well known to be a money pit to attain the accuracy of an AR, and then more money to keep it there. If the gun didn’t have sentimental value to me (it was my first gun purchase ever), I probably would have sold it in favor of an AR based platform.

I was planning on an AR-10 at some point. But for my intended use, I thought this project woud be a nice middle ground between weight and capability.

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Make sure that you note that this is “calculated” data from an unknown person on an internet forum 8 years ago.

If all that you are doing is punching paper, then any caliber will do. Using .223 with a 77gr MK will produce consistent results on paper out to 1000m provided that you become accomplished with range finding and estimating wind speed. You will be able to afford to practice more in order to master these skills. If you are wanting to actually take game at longer ranges, then you need to understand long range terminal effects…and kinetic energy calculations are almost worthless in that regard. Spitzer type bullets depend on three types of wounding in order to do more than make ice pick holes. Early yaw to produce tumbling, early yaw to cause fragmentation wounding, or high velocity AND momentum to produce effective expansion. Almost all intermediate type rifle calibers loose both of these abilities at around the 300m range. A larger caliber with a heavier projectile retains more momentum as it impacts a target, and this momentum keeps the projectile moving fast enough as it penetrates to cause fragmentation or expansion of the bullet. Generally, a well designed .308 bullet will still exhibit reliable fragmentation and expansion characteristics well out to 600m. Beyond that, it becomes a tumbling .30 caliber projectile which is still fairly effective. Early upset to cause a tumble is also dependent on the weight distribution of the bullet. Longer bullets tend to take longer to destabilize and yaw. The ideal shape for a rapidly tumbling bullet is a teardrop(triangular), with its weight distribution shifted to the rear of the bullet. When the bullet destabilizes due to reduced spin, the heavier rear wants to lead, so the bullet flips. Elongated bullets designed for ultra high sectional density, high ballistic coefficent, and high accuracy at long range sometimes will not flip until the bullet has already passed through the body. Take for example the 6.5mm Carcano:

Some bullet designs such as the 5.45x39 with the hollow nose which is designed to have that light front and heavier rear, actually deform on impact so that the core dislodges from the rear and ends up in the front of the bullet. The result is a bullet that doesn’t have the weight shift, and doesn’t tumble.

So, if you want a long range caliber that retains an excellent wounding mechanism you want the larger and heavier caliber.

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I’m getting the idea from the last few posts that I would be better off just building a “long range” AR15 in 5.56 and my original 30-06 project. That way, If i really want to try the 6.5, I just pick up the upper of my choice and go.

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If that is your goal, then your .30-06 project is probably going to be your best choice. A “capable” medium-to-large game hunter at 600 yards will require a full power rifle cartridge. .308 would be the minimum in order to get ideal terminal effects at that range. However, at that range I wouldn’t trying taking anything larger than a white tail unless you are using a .300 Win Mag. I once shot a mule deer at an estimated 500m with a .308 Hornady 168gr SST, and it ran 1/4 mile before dropping. Mulies that I have shot with the same load at 100m have dropped rather quickly. You just loose too much in the way of terminal effects at longer ranges, and when that happens you are dependent on the size of your caliber and how quickly the bullet will yaw.

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The whole reason why the 308 Win./7.62x51mm was created was to
get .30-06 performance out of a shorter, stronger, and more
modern case design.

The .30-06 does have the advantage over the .308 Win. in that it
can use slightly longer/heavier projectiles vs. the .308 Win. cartridge.
Although, at the expense of a longer action…

Both the .308 Win. & .30-06 Springfield are very caplable cartridges
both being able to take any North American game at sane ranges…

Just my two cents…YMMV.