[constructor]

We all know the 6.8 is great at killing hogs and deer, no doubt there but I question other rounds and their ability VS each other.
IF we compare barrels 7-8" long(obviously all subguns 15" overall length) and shoot each 9mm 124gr (apx 1375fps), 300BO 110gr(apx2000fps), and 5.56 62gr(apx2350fps) which comes out ahead? I know the 300 using 110gr bullets will have more energy but energy isn't everything. To make things close lets say all bullets are expanding hollow points. What is your opinion? Does velocity ever become more important than energy?
I don't believe the BS about 24" penetration needed.

 

[leatherneck]

I think in this application, the 300BO actually gets it right. It is a good balance of projectile weight and velocity. Combine that with a purpose built, bonded, expanding bullet, and I believe it could/would outperform the others.

The pistol caliber(s) are certainly lethal and effective, but they lack the powder capacity to fully utilize a barrel over 5" and as such, are hindered by the case volume/velocity. The 5.56 is also certainly lethal and effective, but as a true rifle caliber, it is hindered by the short barrel/reduced velocity and coupled with a light projectile range due to caliber.

I love the hydrostatic shock and trauma a hit from a high velocity projectile gives, but at the end of the day, reliable penetration to the vital organs is the key to hasty incapacitation. And this primarily comes from higher kinetic energy.

But...at best I am a student in the topic.

 

[constructor]

An AR pistol with a 7-8" barrel and a folding extension tube is apx 15-16" folded and under 5lbs with normal parts. Makes for a handy small pack gun. In this case and IMO the 300 would be versatile with subsonic and supersonic ammo.

 

[kristoffersonblain]

For me the under 10" are 277 wolverine. Over 10" 6.8spc. Makes it nice when midway has bulk gold dots to stock up.

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[JoshT]

Interesting question and I like for the most part what leatherneck said, but I'm still not adding a 300bo to the stable. I don't want to insult my other guns by making them shack up with Michelle's wife.

Jokes aside, I'm just spit balling here, but why limit to 7-8" long barrels. We're obviously talking about AR compatible calibers here and most ARs will be in the 14.5" (pinned/welded) -18" range. I agree with Leatherneck's statement about pistol calibers not being able to take full advantage of a rifle length barrel, but those lengths open up the viability of other rifle cartridges. IE 450BM, 458 Socom, 6.5, 7.62, and ofcourse our favorite 6.8, any of which can be found in loadings and bullets optimized for the barrel length and desired usage. If you desire something more along the lines of a pistol caliber, they are chambering AR in 45ACP now and require much to take it to a 460 Rowland chambering, which could probably benefit from a greater than 5" barrel length. That'd have the benefit of being able to run anything from 45 ACP to the 460 Rowland.

For the purposes I think are discussed here, of what I've got, I think I'd take the 12.5" 6.8SPC loaded with XM68GD or the 16" 450 BM loaded with anything. But more likely any of the 16" rifles (.223, 6.8, 450) to avoid the potential legal aspects of using a registered SBR or AR pistol in those situations. After using it, I'm really not that fond of shooting an AR pistol.

 

[ozarkpugs]

Impact velosisity is only part of the picture , the bullet has to maintain that velosisity to get her done. As far as 24" penetration goes I think a bullet needs to have enough penetration to reach and penetrate both lungs . If that is 12" 24" or 36" so be it . Of course an exit is great but dead is dead .

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[Ratdog68]

What is the objective of this weapon? What is the intended kill? What distance is the expected killing performance?

 

[constructor]

What is the objective of this weapon? What is the intended kill? What distance is the expected killing performance?

It isn't hunting. Small pack gun 17" overall length max and under 5lbs with a red dot. Probably way under 100yds but 150 max. Must be 100% reliable so no weird cartridges, the 300 came up as an afterthought.

 

[kristoffersonblain]

H does this mean you would consider making a batch of blackout barrels?

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[leatherneck]

JoshT, remember, the specs set for the scenario are a 7"-8" barrel.

I agree fully that when going as long (respectively speaking, of course) as 10" plus, then you can really start to see the gains of a 6.8, as well as others.

But in a PDW sized weapon, I think there are better choices than the 6.8 SPC, but it is splitting hairs.

It wasn't specified until Constructor's second post, but if you add in suppressed and subsonic, then other calibers really start to shine.

And with a barrel length/weapon of that size, I am assuming here, but the max intended range would be quite short and in the reality of pistol calibers, 300BO, etc

 

[leatherneck]

I don't own a BO, but have considered one on more than one occasion. But my thoughts are for the very same size package as indicated in this discussion. Suppressed; absolutely (as an option when OAL is less restricting or scenario). And then the suppressed & subsonic availability really opens up the scope of applications.

 

[leatherneck]

Also, to add, my issue with large bore AR calibers in the situation that I think we're discussing here is this:

-total magazine capacity
-overall reliability
-recoil and muzzle blast
-suppressor capability/availability

They are the energy kings, however, and will put down what they hit.


In cartridge and weapons choices, and everything in life really, it's all about balance and versatility, in my humble opinion.

 

[constructor]

H does this mean you would consider making a batch of blackout barrels?

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No not even remotely considering it, this is just a special project for myself. I have a maxpedition Kodiak sling pack that is perfect for a get home bag, 17" is the max length it will handle. I have an A3 Stribog (9mm) but I started questioning it's ability and why am I jacking around with it to make it 100% reliable. I know ARs but also know a 10" will not fit in the pack without separating the upper and lower. Pistol gas system ARs are the worst possible AR and I hate the thought of it but...if it works

 

[Guts]

Very interesting question. Great thought provoking number for speed, caliber and weight. In the end, I think I'm with Leatherneck.

I'm not a fan of the 300BO, but in this hunting scenario I think it is the best option. The 9mm is compact and is designed for expansion at lower FPS so I'll go with it on a close second over the 5.56. Speed is the multiplier for kinetic energy. Mass outweighs (pun intend) speed for momentum needed in lower speed penetration. Even if the 5.56 managed to out penetrate, it lacks diameter to make an effective wound channel, even with HPs. In close, the BO and 9 are at their optimization, the 5.56 is already below optional performance.

If ranges are longer than 75-ish yards, I might give the the nod to the 5.56 over the 9, because the 9 is losing volosity the quickest. If ranges are much over 150 yards, the 5.56 might win this race overall? However, the 6.8 comes out on top in all scenarios.

But that's just me.

 

[kristoffersonblain]

No not even remotely considering it, this is just a special project for myself. I have a maxpedition Kodiak sling pack that is perfect for a get home bag, 17" is the max length it will handle. I have an A3 Stribog (9mm) but I started questioning it's ability and why am I jacking around with it to make it 100% reliable. I know ARs but also know a 10" will not fit in the pack without separating the upper and lower. Pistol gas system ARs are the worst possible AR and I hate the thought of it but...if it works

While I love my 12.5" 6.8, for this project, if you want factory ammo 300 blackout, if you reload the 277. My biggest complaint with my blackouts, aside from lacking energy, quality bullets designed for its velocity aren't cheap whereas 6.8 you can get bulk gold dots and speer tnt's.

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[wintys]

I'm not a .300AAC fan at all besides playing with subsonic heavy's with the grand kids but a 110 grain varmint round would probably be hard to take as a personals protection round, as far as hunting with a BO, it's not for me ....

 

[Subeng]

I know they are the guys that left and did their own thing but I've been watching the 40 GPC, basically a straight wall 6.8 case in 40 caliber, like a hopped up 40 S&W. Sounds interesting, sort of a 10mm magnum?

 

[Ratdog68]

It isn't hunting. Small pack gun 17" overall length max and under 5lbs with a red dot. Probably way under 100yds but 150 max. Must be 100% reliable so no weird cartridges, the 300 came up as an afterthought.

Ok, disregard... the Mossberg Shockwave does not fit the parameters of your dimensions for means of transport.

12 ga. Pump Shotguns | Page 2 | 6.8 SPC Forums (68forums.com)

 

[navy6.8]

I would suggest 7.62x39 but for 100% reliability you would have to probably go with a lower that takes ak mags. I have had great luck with my acs mags they run 100% but that is a sample size of 3 or 4

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[Nativeman30]

Love my 10mm banshee. Chrono'd my 180 grains at 1450 fps out an 8" barrel. Heavy bullet isnt everything. Remember Energy is mass x velocity^2. Increasing the mass provides a linear energy gain, increasing velocity provides an exponential gain.