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Old February 4, 2015, 06:52 AM   #1
Shooter2675
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Best Second Caliber for My AR-15

I am looking at building another upper for my AR-15, and can't decide what caliber to build it in. I had narrowed it down to several calibers, the .50 Beowulf, 6.5 Grendel, or the .300 Blackout. I was also looking at the 7.62x39 but the commonly reported feed problems deterred me. I don't really have a specific reason to buy any one of them, but I guess I would be mostly target shooting at 100 yards and hunting. I like the idea of a more powerful caliber in the .50 Beowulf, but based on my ballistics software, the 6.5 Grendel overtakes the Beowulf in power under 200 yards. The .300 Blackout would be neat but I would likely never use a suppressor so I cannot see what it would offer me that the Grendel wouldn't. Right now I am leaning towards the Grendel, but the Beowulf just seems like a neat concept for an AR-15. If I were to build the Grendel, it would likely be more of a long range shooting caliber, whereas a Beowulf I would use more as a close range target shooting and hunting gun. What are your thoughts on this?

John
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Old February 4, 2015, 08:16 AM   #2
mardanlin
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I'd personally go with the 6.5.
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Old February 4, 2015, 09:03 AM   #3
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For hunting I went 6.8SPC.

Most shots hunting are less than 200m, which is a good case for the .300BO if used supersonic, but it doesn't have as flat a trajectory. Both it and the 6.8 are better from a 16" barrel than 6.5, which loses more fps as you cut it down from it's designed length of 20" +.

Parts are much more readily available for 6.8 vs 6.5, and the bolt face of the 6.8 isn't cut away as much as for the 6.5. The market is pretty flush with cheap barrels for .300BO, but you get what you pay for. Most barrels for 6.8 are better grade than milspec and have the improved chamber.

If hunting included antelope or prairie dog, the 6.5 has the edge, but in woodland use with the shorter barrel, the 6.8 is much more popular hunting whitetail and hog. Cheap range plinking? Keep the 5.56 for that.
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Old February 4, 2015, 11:07 AM   #4
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I'd say 6.5, 6.8 or anything designed for the AR, but something that is useful should you need it for other than plinking. Not sure if you're planning on hunting...
Really I think it would depend on availability of a certain ammo. Should be an improvement over 5.56 or 7.62x39
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Old February 4, 2015, 11:22 AM   #5
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I have an AR in 7.62x39. The feeding problems are over-exaggerated (unless you get them). I use mine for hunting dark timber.

That said, a 6.5/6.8 has more oomph for hunting and shoots flatter than my choice. And if you're not going to be blazing away all day, neither ammo is going to be a major expense.

If you were going to be hunting really big ticket animals, I'd say go 450 Bushmaster, 458 Socom, or 50 Beowulf or something with even more power...
Happy hunting.
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Old February 4, 2015, 12:36 PM   #6
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The least expensive way is 300blk. All the same parts as a 556 build, except the barrel. You could even use the bolt and BCG out of your current AR.

Very similar balistics to the 762x39 that you mentioned being interestred in. Hunting UNDER 200yds is not a problem. 110gn barnes blacktips are a proven winner there.

You say no suppressor in your future...does your state allow SBR's. Thats where the blkout shines. Very little loss of velocity with a short barrel. The other calibers are dependant on longer tubes to get the FPS that makes em "better"

I have a 9" 300blk and its as handy as a rifle can be. Would make a great heavy brush gun for deer/pig sized game
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Old February 4, 2015, 05:57 PM   #7
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I like the .300 BLK, just I am not sure what it's purpose is. It is legal for me to do both a silencer and sbr in my area, but I have no desire to do either. For me, I think the 6.5 Grendel would be better because it has more energy and long range power. I think the blackout would be great for a sbr or silenced setup, but like I said, I have no desire to do that. About the 6.8 spc... What advantages does it have over the 6.5 Grendel? It has a .3 mm larger diameter but it has worse ballistics and its BC is no where near the 6.5 Grendel. I think now I have eliminated the .50 Beowulf, so for me it's now between the 6.5, 6.8, and .300 BLK. I guess the 7.62x39 could be in the mix I am just not sure for what reason.

John
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Old February 4, 2015, 08:04 PM   #8
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If not doing an SBR or suppressor AND if max downrange ballistics are important then i would go 6.8. Or maybe the new 277 wolverine.

I think one of the advantages of the 6.8 over the 6.5 is bullet selection options
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Old February 5, 2015, 06:51 AM   #9
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Ok, so the availability of bullets plays a role in the 6.8's advantage. But bother than selection and availability, it is worse ballistically, right?


John
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Old February 5, 2015, 06:20 PM   #10
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The more I think about it, the ability of the blackout to use the same bolt and mags sounds really appealing. Any reasons not to get the .300 AAC Blackout? It would be in a 16 inch barrel unless someone can convince me that the SBR application is simple enough.

John
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Old February 5, 2015, 06:26 PM   #11
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I chose the 6.8


If you want to use the same 223 brass, bolt and mags, (and you reload)

You should also seriously consider the .277 Wolverine

It takes the 6.8 bullets in 223 brass

The awesome 100g accubond bullet will stay at or above 1k ft lbs out to 200 yards (the best bullet I could find in 300blk drops below 1k ft lbs at 125 yards)

They also are doing well with the cheap Sierra 110g bullet

The reality is, they are all good......
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Old February 5, 2015, 06:57 PM   #12
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I like the idea of the .277 Wolverine, but I would prefer a cartridge that has factory loaded ammunition. It looks great but I would get the 6.8 SPC or the 6.5 Grendel over it as I think the extra power would be worth the cost of an extra bolt and mag. Their really isn't anything more powerful available in .30 cal for the AR-15, is there? I mean more than say 150 FPS velocity gain than the .30 blackout.

John
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Old February 5, 2015, 07:12 PM   #13
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The 300 BO/Whisper/Fireball is the best option if you want a surpressed SBR for short range work. I had a Whisper years ago and it was decent inside 100 yards, but I wanted more and after shooting both the 6.5 and 6.8 I went with the spc.

If you plan on paper punching at 400-800 yards, the Grendel is better thanks to the 123gr 6.5 has a much better BC, but the 6.8 is not as bad as the Grendel crowd would have you believe. Once you step away from the Amax and Senecar and look at the good hunting bullets, the Grendel is not so awesome:



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Old February 5, 2015, 09:20 PM   #14
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The grendel is a good option, but to really wring out the distance a longer barrel is needed

For hunting, I like the 16 inch barrel as being very handy.....and.... I am never taking a shot over 300 yards anyway

The 6.8 with the 120g hornady SST clobbers the texas boars big and small

The factory load falls below 1k ft lbs at 275 yards.
(it's my DRT bullet.... Dead Right There)
Most of the animals I hit with the 6.8, never take another step


You really have to decide what YOU want the rifle to do

You will enjoy your choice more when it fits the application desired

The 300 Blk - People that have them seem to love them. Very popular choice. They take game well at limited distances, but well within what most people hunt in. (to 150 yards) They can be suppressed better than them all
Cheap brass pickup for reloaders is an awesome advantage. They seem to do well with cast.

The 6.8 - A popular choice, very good for short to longer mid range hunting to 300 yards. No real suppression option. (This was my choice)

The 6.5 Grendel - popular choice. the distance king of the group.

277 Wolverine - New caliber, I think this one has some legs to grow


You really cant go wrong if you chose any of these.

Isnt it good to have 4 choices (many more) and know that EVERY step is right?

Good luck with your choice.......
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Old February 5, 2015, 09:34 PM   #15
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Quote:
t would be in a 16 inch barrel unless someone can convince me that the SBR application is simple enough.
The Form 1 application is SUPER simple. You can do it on line with a trust and approvals are running at about the 30day mark. The downside is its going to cost an additional $200 for the tax stamp from the ATF.

It really is very simple. There are even step by step tutorials on line.

I dont hunt and if im going to punch paper at more then 200-300 yards then i use a bolt gun in a suitable caliber with a proper optic

For a fast and nimble rifle inside 200 yds.. My 9" 300blkout SBR is my first choice
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Old February 5, 2015, 11:44 PM   #16
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"Both it and the 6.8 are better from a 16" barrel than 6.5, which loses more fps as you cut it down from it's designed length of 20" +."

Usual internet BS from the usual source...

Using the same unbiased, reliable source with similar weight bullets...

From a SHORTER barrel than the 6.8 (14.5" vs. 16") the Grendel is maybe 100 fps slower at the muzzle...

At just 75 yards the 6.5 Grendel is THE SAME velocity...

And EVERY YARD after that the 6.5 advantage is more and more!


"I think one of the advantages of the 6.8 over the 6.5 is bullet selection options"

Perhaps you should look at the selection of 6.5 mm bullets...

And, ALL of these bullets are reloadable in the 6.5 (although the very heavy 155g+ bullets have no real use in the Grendel) and the 6.5 Grendel is best with bullets of 130g or less...

On the other hand, manyif not most of the .277" bullets designed for the .270W and larger cartridges are unsuitable in the 6.8...

T.
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Old February 6, 2015, 03:10 AM   #17
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If you are looking at 6.5 Grendel and 6.8 SPC (II), and care about bullet selection, then 6.5 Grendel wins.

You may find, however, that just because you can use a bullet, doesn't mean that it'll work well or achieve the goals you set for the bullet....


A while back, I was all set and ready to order the necessary parts, reloading dies, brass, and bullets, to build a .264 LBC (non-proprietary 6.5 Grendel).

But, literally just before I was about to click the "checkout now" button to order the dies, brass, bullets, and upper receiver parts, I realized that the arguments about "more energy" "better ballistics" etc. were completely lost on me. In the situations that I would be using that rifle, the difference between 6.8 SPC and 6.5 Grendel wouldn't matter. And, for that matter, neither of them would really be any better than .300 Blackout.

So, I built a .458 SOCOM instead.
I love it.
Of course, if you don't reload, .458 SOCOM ammo will cost you one testicle, 12 gold fillings, 3 toes, and your first born child, per 20 rounds...
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Old February 6, 2015, 03:19 PM   #18
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FrankenMauser,

At the rate I like to shoot it sounds as if the .458 will cost me my manhood after only 40 rounds ! But seriously, is setting up a trust fund that easy? The engraving on the lower sounds like a PITA though.

John
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Old February 6, 2015, 03:33 PM   #19
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Setting up a NFA trust is also super simple. Lots of places online will do one for you. 199trust.com is an example.

Engraving is not hard either. You can send the lower to a number of professional engravers and get it done fast and beautifully finished. Lots of options on where on the lower it can be done.

Front of magwell. Along the bottom lip of the magwell, on the bottom of the trigger area. Can be as discreet as you want. The ATF has size and depth requirements, but engraving NFA itsms has become a niche industry. Lots of companies do it all the time.

I was hesitant to get into NFA, because i thought it was hard. Not so at all. Last year alone i did 3 SBR's and 4 Suppressors. Easy stuff, really.
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Old February 6, 2015, 05:31 PM   #20
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Can you put a suppressor on a SBR? Because that would make 2 NFA items on one gun. Does the suppressor also need an engraving?

John
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Old February 6, 2015, 06:39 PM   #21
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Can you put a suppressor on a SBR? Because that would make 2 NFA items on one gun. Does the suppressor also need an engraving?
Both the SBR and the Suppessor will have its own tax stamp so both on 1 platform is fine. Some guys permanently attach the suppressor to the short barrel, bringing the total barrel length to >16". Now you dont have an SBR, so its only 1stamp and only one $200 tax. Kinda like pinning a long flashhider to a 14.5" barrel to make it over 16"

The only time you need to engrave is if YOU make the item. So if you take a 16"barreled AR and put a 9" upper on it, you have "made" that SBR. You do that via a Form 1 application to the ATF and pay a $200 tax for that item.

You can make a suppressor the same way. Do a form 1, pay the tax, once approved get your lathe turning and make a can. THAT can would need your info engraved as the "maker"

Most cans are built by a manufacturer and then TRANSFERRED to you (or your trust) on a form 4. You find a dealer that has the can you want in stock. Fill out the Form 4, pay the same $200 tax. Once its approved you go pick it up at the dealer. He will hold onto the can while you wait for approval
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Old February 6, 2015, 07:01 PM   #22
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I understand it may sound easy to you, I just don't have the motivation nor the real desire to do a SBR. For me all the short barrel would do is hurt accuracy and velocity. I am, however, interested in the .277 Wolverine. Where could I find load data for it?

John
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Old February 6, 2015, 11:11 PM   #23
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I just watched a video with the .50 Beowulf and it looks pretty sweet, it's so hard to decide on a caliber! Does anyone know how many reloads you can get with one .50 Beowulf case?

John
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Old February 7, 2015, 12:22 AM   #24
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Quote:
Originally Posted by Shooter2675
I am, however, interested in the .277 Wolverine. Where could I find load data for it?
http://mdws.forumchitchat.com/
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Old February 9, 2015, 11:52 PM   #25
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Which caliber?

I have several AR's in 5.56 and recently got a Rock River 6.8 spc with a 5.56 upper. The 6.8 is a caliber apparently the Army is using but the ammo is hard to find and expensive right now (+/- $1 a round). The .300 BO is about the same but reloadable from .223 brass as the 6.8 is not. Heavier hitter and longer distance its the 6.8 but for normal use the 5.56 is my go to caliber.
A lot of the decision is going to depend on what calibers are still around in a couple years, cause what the Army is using is the ammo that will get manufactured the most with spill over to us cillyvillions. I just hope the 6.8 does not become like the .450 Marlin...
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