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Old January 19, 2020, 01:30 PM   #1
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Alternative AR cartridges

Okay, the truth is I've done tons and tons of reading about, but very little shooting of AR pattern firearms.
What are the Pros/Cons of getting an upper in alternatives to 5.56?
Really looking at 6.5 Grendel, 6.8 SPC, 300 BLK, and 350 Legend. Mainly for more oomph. I read 300 BLK and 350 Legend have relatively shorter ranges, but again, I've only done some reading. Looking for more first hand experiences.
Why do you shoot an alternate cartridge? Is it worth it?
Are you thinking of getting a different upper? If so, why?
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Old January 19, 2020, 02:07 PM   #2
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I was into 6.8 SPC when I lived in Texas hunting hogs. The difference was appreciable, especially with copper solids. I’ve since moved to a state without a hog problem so I’m trying to sell my 6.8 parts and components because my AR use is just target now, and 5.56 is the king of cheap ammo (aside from 22LR). I don’t think there’s a benefit to more oomph unless you’re hoping to deliver the oomph on something with a pulse, but in that case there is definitely a benefit in my experience
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Old January 19, 2020, 02:27 PM   #3
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As it is I can do anything I need to do with my AR's in 223. Bullets ranging from 40-90 gr covers a lot of ground.

But if I were inclined to go with something else the 6.5 Grendel is the one that most interests me. I keep hearing rumors of some type of new military round in 6.8mm.

Depending on exactly which direction that heads I could be interested in going with that. But that depends on exactly what they come up with. At this point this is an unknown. The 6.5 Grendel is pretty proven.
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Old January 19, 2020, 02:29 PM   #4
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I have 6.8 stuff for when I move back to Texas. I too was a hog hunter that moved away from Texas. If you venture out, I’d initially suggest something like 6.8 because it’s been around a longish time and most known bugs have been worked out.
Really depends on the application of the firearm.
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Old January 19, 2020, 03:15 PM   #5
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I have pretty much tried them all, just for fun and paper punching. Really like 458 SOCOM, 450 Bushmaster and the 6.8 SPC. I have a 300 Blackout, but would like to try a 300 Hammer next. Just finished a 22 Nosler, am initially disappointed, but I only fired about 4 or 5 factory rounds to zero the scope before the serious arrival of winter put the brakes on the project. I have parts for a 6.5 Grendel but want to send the main parts out for digital Navy camo (blue) hydrodip before I build it. For a first time departure from the standard chambering I'd try 6.5 Grendel or 6.8 SPC. Both mine have Ar15performance barrels.
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Old January 19, 2020, 06:26 PM   #6
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As it is I can do anything I need to do with my AR's in 223. Bullets ranging from 40-90 gr covers a lot of ground.
I agree, and all but a few of the animals I’ve hunted and killed, I done with my Mini14.

After realizing that way more options lie in the modular nature of the AR style rifles, I started assembling ARs for different purposes.

Right now these things are cheap enough to have one in every caliber you want.
I’ve got at least three different uppers for each lower... some I’ve never fired yet.

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Old January 19, 2020, 06:50 PM   #7
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I fired my first shots from a 6.5 Grendel 20" PSA upper today. It took a while to get the adjustable gas block dialed in but it seems to function well now. The set screw doesn't seem to keep the gas screw from moving and there were no instructions on how to adjust it. I'll need to come up with a way to lock the gas screw down but the upper is working. Next time, I'll sight it in and check the accuracy.
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Old January 19, 2020, 08:43 PM   #8
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Given that Elliottsdad is of Glenwood, Iowa; there is a distinct advantage in going with the straightwall cartridge if there is any chance of wanting to use it for deer hunting.

There is a decent chance of getting a good shooting 350L in a mid range AR platform.

If you are confident in not wanting to use the gun for hunting deer, can you tell us what use you are thinking of that needs something other than a 223/5.56.

If you are thinking of longer ranges, a 6.5 or 6.8 has better ballistics, but appropriate guns & ammo will typically be more costly. Local laws limit using this round or any other bottleneck.

For anything resembling "hog shooting" the 300 BO can generally get the job done. However, the 7.62x40 and 300 ham'r are better than a 300 BO, but again there may be a little more cost. For hunting at 100 and beyond, the extra cost is probably worth it in terms of both harder hitting and more likely to shoot accurately.

If you want really hard hitting, there is the 450. However, it tends to hit hard in two directions with each shot. Ammo and guns are generally not cheap.
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Old January 20, 2020, 09:01 AM   #9
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I’m not a fan of 223/5.56. I’ve had 2 or 3 ARs chambered in them and just never came around to enjoying the caliber. It actually really spurred me on the platform until I shot a friend’s that was in 7.62x39. That got me hooked. So when I built my last AR, I went 7.62x39.

It’s an affordable round that is more than capable at any of the distances I’d use this rifle at, roughly 50-200 yards. With cheap Wolf ammo, it’s looking to be a 1.5-2 MOA rifle when I don’t mess the group up. Which is plenty for my uses of paper, steel and absolute worst case scenarios.
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Old January 20, 2020, 01:44 PM   #10
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In the category that you're looking at, I'd lean toward 6.8 SPC. It's a good cartridge, and easier to deal with than many of the alternatives.

I have thoroughly enjoyed my .300 Blk, however. If you find the cartridge interesting, it's an easy one to adopt. No special magazines needed. Ammo is readily available. It is easy to reload. And, if you are so inclined, it suppresses very well.


I've had five .223/5.56 AR uppers (possibly six?), not counting constant reconfiguration of three of them, the entire time that I owned those barrels/uppers. I've just never been happy with any of them except the 7.5" pistol (which has remained unchanged since it was first assembled).

.223/5.56 just doesn't get me excited unless it's combined with something odd, like the 7.5" pistol or a super-heavy, extra long varmint barrel.
Three (four?) years ago, I finally got a "5.56 Match" chambered, long, heavy, straight .930" barrel that I really liked, which shot quite well. But I wasn't happy with the lower and I wanted the barrel threaded. I assembled a new semi-dedicated lower two years ago, and had the barrel threaded very shortly afterward. While it was torn down for barrel threading, I stole the scope for another project and have not replaced it. It has not been fired since being rebuilt two years ago. Not even for function testing...

On the other hand, I've fired at least 5 times as much ammo through my single 6x45mm upper as .223/5.56 has been fired through all of the .223s/5.56s, combined, over the last five years. That upper was also rebuilt to substantially reduce weight. But it has been fired quite a bit since.

I'm also currently still working out the bugs with a .17-223 upper that was assembled with the parts removed from the 6x45mm upper during its remodel.
For all the headaches that come with this seemingly ridiculously simple wildcat (it's not true!), I've still fired the .17-223 four to five times more in the last year than all of my .223s/5.56s over the same time period.

Even the .475 Tremor (.458 SOCOM necked up), which is also a pain to load for, and averages about $1 per trigger pull, gets fired substantially more frequently (though in lower volume) than the .223s/5.56s.

As of now, the .300 Blk trumps them all, though. Over the last two years, I've fired hundreds more rounds through the Blackout than through everything else. It is more expensive to shoot than everything but the .475 Tremor, but also a lot more fun. (Especially since I primarily shoot subsonic loads with a suppressor.)

I like .223/5.56. I think it is a good cartridge. But when it's time to grab an AR and head to the range, or mountains, or desert, I rarely reach for a .223 or 5.56. And if I do, it's usually the 7.5" pistol...
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Old January 20, 2020, 10:56 PM   #11
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I'm honestly most interested in what the 6.5G and 6.8Spc can do.
The 350 Legend isn't nearly as sexy ballistically, but as P Flados pointed out, I'm in Iowa. I can't imagine hunting deer with an AR in the near future, but being a straight wall-only hunting state, I am considering 350 as a practical geographical choice.
I just don't wanna get stuck with so-so ballistics due to these game laws. If the laws were to change for some reason, we'd have no further use for 350L.
And then I'd kick myself for not going with my gut and choosing a ballistically superior cartridge to begin with.
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Old January 20, 2020, 11:21 PM   #12
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The 6.8 was my first alternative AR caliber and still one of my favorites. Mine is mainly used for hunting hogs. The caliber is easy to work up an accurate hunting load and ammo is usually available locally or online. Only difference is barrel, bolt and magazine. I use to carry a .308 AR for hunting. But don't miss the extra weight of the AR10 in the field.

Also have 270AR (wildcat), 6.5 Grendel and .224 Valkyrie in alternative calibers. Of those three, the Valkyrie is my favorite for the extended range it offers. It requires a 6.8 bolt and mag. I like the 6.8 brass it uses plus the heavier .224 bullets. I have a huge stash of the those bullets and the 6.8 brass.
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Old January 21, 2020, 02:53 AM   #13
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but being a straight wall-only hunting state, I am considering 350 as a practical geographical choice.
If that's an important criteria, unless you're recoil sensitive I'd recommend 450 BM over the 350L since it was purpose-built for AR's and has a long track record of being successful and reliable for hunting in those states that require straight-wall.

ARP is something of a "boutique favorite" among many AR builders for barrels as they have very affordable barrels that usually deliver outstanding performance. I just received notice from Wilson Combat--who I also have bought barrels from--that the 300 HAM'R has been anointed by SAAMI as an official SAAMI cartridge. They have a 110 gr tax cartridge getting 2600 fps--but I and others have equaled and exceeded 2700 fps with ARP's tac30/30HRT using a 125 bullet. Wilson must have rushed their advertising to press--they also list a 50 gr fusion at 2300 fps (they probably meant 150 I would think). On the other hand, it's interesting to note that Wilson in rolling out their version of the 300 HAM'R also was smart enough to offer a comparatively huge line of ammo for the hunter. If only winchester had done that with the 350 legend, right?
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Last edited by stagpanther; January 21, 2020 at 06:41 AM.
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Old January 21, 2020, 10:19 AM   #14
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7.62x40 and 300 Ham'r are not more expensive if you catch the barrel on sale and do the swap yourself. The barrel and 300 BO compatible magazine is all you need. Also, compare the twist of the Wilson Combat barrels (12 and 15 respectively) are more conducive to the bullets (including cast) that are being used.

One other thing. While anything not 5.56 style bolt heads with less metal near the locking lugs seem to be working okay, I prefer more metal at that point and any 5.56/.223 case head fits the bill.

But, I like the 6.5 Grendel,... a lot.

Both 7.62x40 and 300 Ham'r cases are easy to make. 300 Ham'r cases are available at both Wilson Combat and Starline and maybe some estores. Dies are available at Wilson Combat and maybe some estores.
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Old January 21, 2020, 11:56 AM   #15
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I'd give the 300 HAM'R a serious look if I didn't already have a tac 30.
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Old January 21, 2020, 12:09 PM   #16
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I think the 6.5 Grendel is the most promising. It's got more oomph than a 5.56/.223 and also has more range. I've got 5.56/.223, .300 Blackout, and 6.5 Grendel ARs. Each have their own purpose. I like the 5.56/.223 for general plinking, fun, and self-defense. The .300 Blackout excels as a suppressed platform. The 6.5 Grendel is good for hunting larger game and reaching out at distance.
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Old January 21, 2020, 10:11 PM   #17
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Why do you shoot an alternate cartridge?
I went to an AR-15 after my oldest, a very small/lightweight daughter, was almost driven out of shooting by the recoil of her .243. With the AR-15, I got reduced recoil, and an adjustable stock that fit her length of pull. I went to the 6.8 SPC because I wanted a more powerful cartridge than 5.56/.223 for my kids to hunt deer/hogs with. When I got into the game, it was before Bill Alexander of Alexander Arms released the Grendel to SAAMI, so you could ONLY get 6.5 Grendel ammo from Alexander Arms. 6.8 SPC was the only commercially available cartridge in appreciable supply. I have not looked back, but if I was making the same decision today, the decision would be harder to make with the Grendel now being widely available commercially.

Is it worth it?
Yes! After 4 Texas whitetails, and 6 Missouri whitetails, and 3 kids all getting their first deer with it, the 6.8 SPC, using Hornady 120gr SSTs, when used within its limits, has done exactly what I expected it to do.

Are you thinking of getting a different upper? If so, why?
Sorta... I had a great deal where I bought complete 5.56 rifles and matching 6.8 SPC uppers configured with 16" bull barrels and solid metal free float tubes with pic rail gas blocks. What I realized too late was that the rig is too heavy for the kids. An 18" medium or heavy profile barrel with low-profile gas block and a lighter free float handguard would have been a much better choice. Some of my kids are looking at ARP 18" barrels and M-Lock handguards.
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Old January 22, 2020, 05:34 PM   #18
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I am a 6.8spc fan, I have had a couple of AR's and a Mini-14 in 5.56 but I was never fan of that caliber and sold them off. I was never interested in the AR rifle until it became available in 6.8spc, now it's my favorite platform.

Consider 5.56 is a .22 caliber bullet and the 6.8spc is a .27 caliber bullet, being a hunter, this is how I approach the calibers. A larger diameter heavier bullet traveling at similar velocities simply has more power, so the question is, why not have more power? The slight increase in recoil is negligible.

I feel this is the caliber the AR should have been developed in in the first place. My last 5.56 AR had a 1:7 twist and didn't shoot 55 or 62 gr. bullets that well, I never used 77gr. in that rifle, but did in a previous 1:7 5.56 AR and it shot the heavier bullets better. Those heavier ones are more expensive in my experience.

The accuracy of my 6.8spcII AR's is astounding and that is just using a red dot sight, if I were to put a scope on them they would be even better. I use the 110gr. Sierra sp tactical loads and the ARP 16" scout profile barrels.

I never gave the 6.5g much thought, but I know there is more metal on the bolt face of the 6.8 then there is for the 6.5 and the 6.8 mags hold more rounds then the 6.5 mags do.

The better attribute of the 6.5g is it's ballistic co-efficient, meaning it flies better, but the 6.8 has better terminal effect. So unless you need the distance the 6.8 will have better terminal effect than the 6.5g within 300 yards.

I don't foresee myself taking shots beyond 300 yards at game, so I don't need the 600 yard ability. Not that the 6.8 can't shoot at 600 yards, it will just be slower and have more drop at 600 than the 6.5.
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Old February 3, 2020, 12:09 PM   #19
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For AR uppers, I have 5 different calibers: 5.56, .22 LR, 300 BLK, 6.5 Grendel and .458 SOCOM. I also used to have 224 Valk upper, but it was an early production barrel that had issues and sold it. I hear most companies worked out the kinks to 224 Valk and is a accurate shooter now.

Why do you shoot an alternate cartridge? Is it worth it?
Each of my different uppers fit different needs. My 300 BLK (on top of my AF pistol lower) is my home defense gun and suppressed shooting gun. My 6.5 Gren (and my 224 Valk when I had it) is for long range shooting (between 500-1000 yards) and the 6.5 Gren can be used on medium game for long range hunting, such as antelope. Of course, my 22LR upper is just for plinking for fun and introducing the AR platform to new shooters such as kids of my friends/family. And the 458 SOCOM is for short range big game hunting. It's a real hog thumper and also good as a semi-auto "brush gun".

I feel it's worth having uppers of different calibers. Especially if they take the same magazine as the 5.56 such as the 300 BLK and the 458 SOCOM. It's cheaper than just buying another gun and it adds a new capability to your AR. It allows you to also focus on that one lower and put a really good trigger (such as a Geiselle) and other parts into it.
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Old February 3, 2020, 01:10 PM   #20
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I went with 6.5Grendel as my alternative AR-15 chambering, for reasons similar to globemaster3: light recoil, less mass, & adjustable stock for a small & young shooter.

6.5G manages medium sized game out to ~300 yards(1) but also has long range target chops.

You can find cheap blasting ammo endorsed by and developed with Bill Alexander from Wolf. And plenty of high quality hunting and target loads, now found in both LGS and big box stores.

The other alternative cartridges all have their utility/niche, but I found 6.5G to have the broadest applicability and utility for my family. Were I to choose another, I likely would go with one of the big bore straight wall cartridges for a short-range thumper and to be straight-wall cartridge compliant on those states that allow such for hunting.

Good luck with your search.

(1) Assuming shooter adheres to manuf guidelines for soft/plastic point hunting rounds.
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Old February 3, 2020, 07:58 PM   #21
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.300blk is popular for hog hunting, does pretty good for defense, and suppresses really well with subsonic loads. It's pretty fun, in my opinion.
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Old February 4, 2020, 06:26 PM   #22
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I'm simple minded when it comes to calibers. Have 15s in 5.56 and 10s in 7.62/.308... isn't anything you can fire out of a 15 that trumps .308 really, so I see no need to get exotic in between.

But if I was going to go there, 6 5 Grendel seems to really shine in terms of range and power, is almost like the .308 alternative for the AR15.
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Old February 4, 2020, 08:03 PM   #23
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The thing I really like about 6.8 SPC II is that it is a sweet shooting little round and works perfectly in both AR's I have had. I think you have to try hard to put together a 6.8 that won't shoot and cycle great.
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Old February 5, 2020, 02:23 AM   #24
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I've been thinking about the .350 lately as I'm a reloader and would love to have a 300 yard .30+ caliber combat capable performer (lol CCCP) and the .350 being straight wall means no trimming and it uses .357 Mag bullets.

IMO, .350 Legend is better than .300 BLK if you're not running a suppressor. I've never been a fan of the .300, I've never seen what it can do that 7.62x39 can't, and with .350 being released in 2019, I see no reason to ever own a .300 BLK.

6.5 and 6.8 are great, but they're expensive, twice the price of 5.56, and I fail to see how they are worth paying double for a civilian. If you want more power (and range) in a semi auto rifle, buy an AR-10 in .308 and you have an easy 800 yard rifle.

But few of us will ever see engagements at distances over 300 yards and as such there are better options vs .223/5.56, so there's plausible reasons to owning a .30 or .35 caliber AR.

All that said, you can live without all the other larger AR calibers just fine as .223/5.56 will do a lot of what you need within 500 yards.
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Old February 5, 2020, 07:19 AM   #25
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I've been seriously looking at the 7.62x40 from Wilson Combat.
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