I think this is the right section since it is concerning ammo lol

I am wondering what has better accuracy and velocity at long range, 300 black out or 6.8

thanks

Both have great accuracy.   300 blackout is basically an accurised  American version of the 7.62x39.  Keep in mind that the velocities are equal to 7.62x39.
As compared to the 6.8spc which with 110 grain is 250 fps faster.  With an 85 grain bullet, the 6.8spc can do 2900 fps.

Depends on your needs and wants.

Apples to oranges. Design objectives are very different between the two. One maximizes energy out of a standard AR while maintaining near full capacity, the other is a dual use cartridge. One thing that is very often left out is the impact of recoil. Travis speaks on this in the video below. IMO there's not much point to a 300blk if you don't plan on suppressing.

https://www.youtube.com/watch?v=tgKjbySsAik

d5griffin
 BS!!!   The 300 blk is a very effective cartridge in the mid range spectrim. Surpressed or unsurpressed!  More energy at 500 yards then the 5.56mm.    When pushing the same wt bullet 110 gr  the 6.8 only has a couple hundred FPS more.  I don't see anything over 115 gr in the 6.8 so thats where the 300 Blk beats the 6.8 all day long !  My 150 gr at 2000 fps! Trumps the 6.8  as it can't shoot a 150 gr anything!   Better yet my 130 gr load at 2200 fps make s the 6.8 look very whimpy!

6.8 85 TSX is 3050-3100 fps from a 16" barrel - handloads can push this bullet to 3200
2900 from a 12" barrel.
110s are in the 2600-2700 fps range from a 16" barrel.



140 VLD is 2400fps from a 16" barrel

I wouldn't really call the .300 an Americanised 7.62x39.  It's not that anymore than a semi auto rimless version of the 30-30.  All three have close ballistics.  If anything the .300 Blackout is a SAAMI spec. 300 Whisper... a few small changes to the shoulder I think.  The Whisper has been around for I want to say 20 years.

okay which one will have more velocity coming out of a 20in barrel, and a 18in barrel

For the 6.8 loads above, add ~100 fps for a 18" barrel and ~150 fps for a 20" barrel.

300 Blackout doesn't gain very much velocity after about 10-12 inches of barrel length...  This makes it ideal for SBR builds...

The reason for this is that 300 blk uses a magnum pistol powder, i.e. you get a complete burn before the bullet has passed the 12" mark.

6.8 is the better mid and long range round, and it isn't even close.  300 is a cool little round, especially in a suppressed SBR, but starts dropping like a rock past 300 yards.

You guys are missing a major point.

Energy is meaningless.  FTLBs do not wound.

Velocity affects drop and this can be compensated for in close to medium ranges, especially with optics.  It also is a 3rd level wounding mechanism, after cutting, then crushing.

If you can compensate for drop, then the only thing that matters is the velocity at target and the velocity required for expansion and fragmentation, the two main wounding mechanisms for normal velocity rounds.  Thats it.  That is all.

6.8 SSA 85gr TSX: MV 3000fps  Bc: .246  Required Velocity: 1800fps?    The bullet crosses 1800fps at 350yards.

300BO 110gr TTSX: MV 2350fps  Bc: .289  Required Velocity: 1300fps    The bullet crosses 1300fps at 425-450 yards.


The BO is still expanding for 75+ yards beyond 6.8SPC.  They are both effective rounds to 350-450 yards.  The 6.8 is not superior until a new bullet pushes it out farther.

If you are shooting 300-500 yards with irons, the drop may prove challenging.  If you are using optics, you should be fine once you learn the round.

I'll add to what I said earlier.

SSA 85gr TSX drops with 100 yard zero:  200: -3.6  300: -14  400: -33.5  500: -65.8

BO 110gr TTSX with 100 yard zero:           200: -6.7  300: -24  400:-55.5  500: -105.5

Both rounds are doable from 0-300 yards with iron sights.  You can no doubt keep shooting both too 500 with irons sights if you know the drops but in all honesty, wouldn't we be using optics at that range.

But the main question is, can you come up 65 inches without much effort while 105 is crippling?  Both rounds require the shooter to make adjustments, is one set that much more difficult than the other?

The BO would be a real challenge to shoot at 700-800 yards for most people, especially to make first round hits with.  There have been reports of soldiers getting hits at 700 yards with 5.56 overseas.  6.8 would have a major advantage here.  But from short to mid-range, the BO is definitely doable.

6.8 95 TTSX 2580 fps from a 16" barrel.
That bullet was purposely designed by Barnes for the 6.8.
Crosses 1300 fps at 675 yards.

-300BLK does not require the bolt-face be opened up and the lugs over-stressed by this change.
-300 BLK does not have the velocity or KE or trajectory the 6.8 offers.

-6.8 will blast the living hell out of your ears in an SBR, and is rough on a blast-baffle on a suppressor.
-300BLK is great in an SBR, as it uses a pistol powder, which incidentally works well in a short barrel. Same for baffles, it's kinder. Much.

-300 BLK holds 30 rounds in an un-modified mag.
-6.8 does not.

-300BLK can be made from 5.56 brass in a pinch.
-6.8 brass is specific, I think, but check me on that.

A lot of that going around...probably explains why there are so many different calibers  

i wonder if 6.8 could have been made from 5.56 size brass like the 300 BLK?



 

Maybe someone should try that. 6.8blackout

there is a wildcat 6x45, white oak still makes barrels for it last time i checked.  its a 6mm bullet jammed into a 223 case.

heres the problem when you start sticking bigger bullets into small cases:  velocity required for bullet performance isnt there.  bullets rely on a certain minimum velocity for expansion/fragmentation/terminal performance.  look at the 300blk.  the only bullet truly designed to work at 300blk velocities is the 300blk TSX.  the rest are just run of the mill 308 caliber bullets stuck into a 35mm case.  most show poor and inconsistent expansion.  the same thing is true with the 6x45.  the same thing would be true of any .270/6.8 bullet stuck in a 223.  you get better performance sticking to bullets designed to be fired from a 223 case.

Its been done by Kurt(7.62x40) and by many others I sure.  Kurt has a thread of all his wildcats on here.  His is a 6.8x41mm that throws the 85grTSX at 2800 or 2900 I believe.  He has also done .25cal, 6.5, and 7mm wildcats on 223 brass and a couple different calibers on 6.5G and X39 brass.  Lots of pics and results in his thread.