300 BO, 6.5 G, or 6 ARC?

[popeye]

These cartridges aren't anything like each other:

300 BLK subs are basically a 45 ACP round with a much higher BC that gives 45 ACP velocity for several hundred yards. Supers are basically 7.62x39, (7.62x39 is a terrible choice for this application due to bolt lugs failing. Super fun gun but not something you want your life to depend on) which gets you out to maybe 400 yds. Realistically subs are a 0-100 yd cartridge, and supers are a 0-250 yd cartridge. You can hit targets well beyond those distances, but as far as a reliably consistent engagement distance, that's what you've got.

6.5 Grendel is ballistically excellent, but the mags/lugs have issues.
6 ARC is ballistically excellent, but the mags/lugs have issues.

Either of these cartridges will have lots of energy, and are a lot of fun for shooting extended distances, but they have their own issues. Sons of Liberty Gunwerks just got behind a new cartridge that they're supporting called 6mm Maxx. Basically it's a 350 Legend parent case (regular 5.56 bolt face) shooting 6mm bullets with a lot of powder behind them. The only problem for the 6Maxx is that you can't load longer bullets in it.

Since your engagement distance is extremely short, the 300 blk probably makes the most sense.

Ikeman83 nailed it!
Of the three cartridges mentioned by the op I have used all of them. The only AR I ever had fail on me was the 6.5 Grendel when the shell extractor broke while coyote hunting. Its a great bullet but the deeper bolt face is an Achillies heel.
The 6 ARC is one of the most accurate AR's Ive owned but it too has the deeper bolt face issue.
I know its not the fan club favorite but for me, the 6.8 SPC delivers the ops desired specs with reliability.

 

[Hoss50]

6ARC is a very fun round that really had good performance for how small it is. We built an upper for my son and it is pretty impressive. Finding brass isn't easy, but the gun shoots well and with 90gr Hornady CX I have no issues taking it on a black bear hunt if ranges are sub-300 yards.

 

[ARlife4me]

6ARC is a very fun round that really had good performance for how small it is. We built an upper for my son and it is pretty impressive. Finding brass isn't easy, but the gun shoots well and with 90gr Hornady CX I have no issues taking it on a black bear hunt if ranges are sub-300 yards.

Looking at 6arc and 6br with same barrel length on quick load, both give within 25fps of each other. My small frame AR (AR15) would be built for 75 and 90gr only (mainly 90fmj). This way I don't have to haul the AR243win around.

 

[Hoss50]

Looking at 6arc and 6br with same barrel length on quick load, both give within 25fps of each other. My small frame AR (AR15) would be built for 75 and 90gr only (mainly 90fmj). This way I don't have to haul the AR243win around.

We are shooting the factory 108gr ELDM ammo to get brass for my son's upper. It is a AR15 upper and shoots the 103gr ELDX and 108gr ELDM well. For the black bear hunt we went on (AZ black bears aren't huge) we switched to 90gr CX mono copper to get a little more solid bullet construction. I am sure my son will use the 103gr ELDX on our javelina hunt next month.

The 6mm ARC in the right hands is fully capable of black bear, deer and down. With the right bullet short range elk is even realistically an option. Not a first choice, but an option. With the low recoil of the ARC a 2nd follow up shot could likely be had.

I will probably look very closely at getting the new Ruger American Gen 2 when they release it in 6mm ARC because of how awesome this AR upper is.

 

[ARlife4me]

We are shooting the factory 108gr ELDM ammo to get brass for my son's upper. It is a AR15 upper and shoots the 103gr ELDX and 108gr ELDM well. For the black bear hunt we went on (AZ black bears aren't huge) we switched to 90gr CX mono copper to get a little more solid bullet construction. I am sure my son will use the 103gr ELDX on our javelina hunt next month.

The 6mm ARC in the right hands is fully capable of black bear, deer and down. With the right bullet short range elk is even realistically an option. Not a first choice, but an option. With the low recoil of the ARC a 2nd follow up shot could likely be had.

I will probably look very closely at getting the new Ruger American Gen 2 when they release it in 6mm ARC because of how awesome this AR upper is.

The biggest thing I'll be shooting is hogs. I know the 6mm 90fmj is capable as I've killed every one (100 or so) with 22cal 55fmj (m193). BA's in 6arc will yield more velocity which could be good.

 

[FireFlyFishing]

When it comes to auto loaders, I like availability of components And/or ammo. 300 BO wins hands down for me here.

With a 110 Barnes coming out of the muzzle at 2400 fps, I think it's a very capable short range round. I look at it as a modern day 30-30 coming out of a better platform than the old school lever action. Plus, if the first Barnes 110 didn't do the job, there's 19 more easy follow up shots that will get the job done.

 

[aschler]

Ikeman83 nailed it!
Of the three cartridges mentioned by the op I have used all of them. The only AR I ever had fail on me was the 6.5 Grendel when the shell extractor broke while coyote hunting. Its a great bullet but the deeper bolt face is an Achillies heel.
The 6 ARC is one of the most accurate AR's Ive owned but it too has the deeper bolt face issue.
I know its not the fan club favorite but for me, the 6.8 SPC delivers the ops desired specs with reliability.

I'm interested in hearing about the failure. A lug shearing off was the main problem attributed to the deeper bolt face but better MOC and lower pressures seem to have fixed it. Extractors have always been finicky for all cartridges, especially as gas systems have gotten shorter. One unique problem with 6.5 Grendel is with the larger rim diameter is you can have to much clamping force, especially if you implement some of the things to improve extraction in other cartridges. Did you have a stronger spring or rubber donut installed?

 

[cajun]

A 223 purpose built to shoot the 77 tmk with 1/7 twist should not be ruled out. Hits way above it's paygrade.

 

[blvette75]

We are shooting the factory 108gr ELDM ammo to get brass for my son's upper. It is a AR15 upper and shoots the 103gr ELDX and 108gr ELDM well. For the black bear hunt we went on (AZ black bears aren't huge) we switched to 90gr CX mono copper to get a little more solid bullet construction. I am sure my son will use the 103gr ELDX on our javelina hunt next month.

The 6mm ARC in the right hands is fully capable of black bear, deer and down. With the right bullet short range elk is even realistically an option. Not a first choice, but an option. With the low recoil of the ARC a 2nd follow up shot could likely be had.

I will probably look very closely at getting the new Ruger American Gen 2 when they release it in 6mm ARC because of how awesome this AR upper is.

Have you hunted any deer or antelope with it?

 

[Dentite]

6.5 Grendel.

 

[Hoss50]

Have you hunted any deer or antelope with it?

Not successfully yet. We have taken it on a bear hunt and javelina hunt but didn't find anything to shoot with it yet.

 

[popeye]

I'm interested in hearing about the failure. A lug shearing off was the main problem attributed to the deeper bolt face but better MOC and lower pressures seem to have fixed it. Extractors have always been finicky for all cartridges, especially as gas systems have gotten shorter. One unique problem with 6.5 Grendel is with the larger rim diameter is you can have to much clamping force, especially if you implement some of the things to improve extraction in other cartridges. Did you have a stronger spring or rubber donut installed?

It was standard BCG, no rubber donut or stronger spring.
Called in two coyotes, shot one and transitioned to the second and was unable to make second shot. Noticed shell was still in chamber so hunt was finished until I could go back home and remove the shell. When I pulled the BCG out I could see the extractor had broken off.
I replaced it, went with an adjustable gas block and haven't had issues since.
After many years of shooting an AR in various calibers (.223/556, 6 ARC, 224 Valkyrie, 6.8 SPC, 6.5 Grendel, .300 blackout and the .308) with many rounds through each, the only one I've ever had a failure in was the 6.5 Grendel.
What was the cause of the failure? I'm not sure but it causes doubt about functional reliability. The depth and thickness of the bolt face are, in my opinion, a weakness. I still like the 6.5 Grendel but if my life depended on it, there are several other calibers I would pick first.

 

[JAYgs8163]

6.5 Grendel brass is easily found. I have 2 of them and love them. One is a AR platform with a 24" Satern barrel and the other is a 22" bolt gun. Both are tack drivers and so easy to load for.

Reload with 6.5 grendel Rifle Brass at Midsouth Shooters

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[aschler]

It was standard BCG, no rubber donut or stronger spring.
Called in two coyotes, shot one and transitioned to the second and was unable to make second shot. Noticed shell was still in chamber so hunt was finished until I could go back home and remove the shell. When I pulled the BCG out I could see the extractor had broken off.
I replaced it, went with an adjustable gas block and haven't had issues since.
After many years of shooting an AR in various calibers (.223/556, 6 ARC, 224 Valkyrie, 6.8 SPC, 6.5 Grendel, .300 blackout and the .308) with many rounds through each, the only one I've ever had a failure in was the 6.5 Grendel.
What was the cause of the failure? I'm not sure but it causes doubt about functional reliability. The depth and thickness of the bolt face are, in my opinion, a weakness. I still like the 6.5 Grendel but if my life depended on it, there are several other calibers I would pick first.

I had the same thing happen with my first AR, a M&P15. It was a very basic rifle 5.56 w/ 16" and I think a carbine length gas system.