I have a complete Spikes ST22 and I’m going to add another upper for it, 300aac or a 6.8. whick one/way should I go?
What is your intended use for this upper?
Do you reload?
Are you planning on getting a suppressor for it?
I imagine you have your bases covered as far as a solid 5.56 platform covered first.
I think the .300 is a specialty cartridge with a specific goal in mind. I would use this if I planned on keeping the distance under 200 meters with the goal of shooting subsonic loads suppressed.
I personally love my 6.8 and feel it does everything the 5.56 does only better. The only downside is decreased magazine capacity unless you go Barrett 30 rounders then you’re looking at extra weight. The recoil is only slightly greater than 5.56 and the round likes shorter barrels. You’re looking at about $1.00 a round with factory ammo. I like having option of bullet weights from screaming 85Gr to heavier 130 Gr that still get around 2400Fps.
It’s all about what you want your rifle to do mang! Also consider ammo availability. I can find a small variety of 6.8 ammo here, none of the .300 cartridges you see. If you reload this disadvantage may be somewhat negated; I’m not a reloader so I can’t expound on this.
There are other things such as bolt/mag compatibility
This is based on my experience which is admittedly limited.
Yes I have three full 5.56 and this ST22, the ST22 is a blast to play with(1.5 hours 250 rounds $9 in ammo), but I am looking to have a AR15 platform with a round with a little more+ Something in between the 5.56 and a AR10 308. The ST22 has a standard AR15 5.56 lower, so pop two pins and you have a different rifle. I am also hunting for a AR10-308. I will end up with a 22, 5.56 and something in the middle and a AR 308
I feel that the 6.8SPC is a great “something in the middle” choice.
The AR-10 style rifles are heavy, there are exceptions but my LMT MWS is hefty as are the mags. It would not be my first choice for a hunting rifle by a stretch. If there were deer or hog sized critters around here to hunt I’d go 6.8 all day long. For caribou I’m kind of a pansy and prefer my bolt rifles for that job although you could do the job with a 5.56/.223.
If you are going to have a semi-auto .308, to compliment your 5.56, the 6.8 is a waste, and unless you plan to use the .300 for very certain, specific things, such as running it with a suppressor on a short barrel, it is simply a money pit.
Keep it simple. Don’t jump on every caliber band wagon, simply because you can.
I guess I just don’t understand the attitude that is seems most of the civilian shooting world has, that more calibers are better, and that, as a civilian, you need thirteen different guns for different uses - the fact is, most people don’t have a real use for any guns, much less all the various “botique” flavors on the market now.
I have to say I agree with this for the most part. I think I like the idea of my 6.8 more than the utility. In all honesty I primarily use it to put slightly larger holes in paper targets.
I am putting together a group of weapons that I plan to use up on a friends ranch in northern Florida to get these wild hogs. They have a major problem up there with these hogs. This is going to be my play time. I have 5.56, SA M1A, Winchester M70 30-06, Moss 12ga. and I will have a AR10 soon. I want to find something in the middle between 5.56 and 308.
Do not reload
No plans for suppressor, but maybe Pvs14 on the AR10. I still have to check with Florida, if can shoot hogs after dark.
I am also re-scoping the M70. I will be putting on a 6x(20-30) long range scope on it. I’m still looking for the right one, I should need a scope with 80+MOA total. I beleive I will need 38-42 internal up moa for a 600-1000yd shot with the 30-06. ???
Heres a vid a member did, where he shoots some plates with 6.8 and 308. https://www.m4carbine.net/showthread.php?t=109606
I do not believe the 300 is only for subsonics or suppressed. It shines with short barrels though. There are lots of threads about the 6.8 and 300 here so I would spend some time looking through them.
If I were planning on a “replacement” or “improved” caliber in what is basically the 5.56 role I would go 6.8. If I were looking for a rifle caliber PDW I would go 300blk.
I DO wish people would stop trying to put the 300blk into this box that says it is only good for subsonic suppressed. Where it belongs is in a different box that represents short barreled supersonic performance with the suppressed thing as a benifit.
Since you are planning on shooting hogs, I’d go with the 6.8, there is a good selection of bullets that will work for killing hogs.
Check out 300blktalk.com, Plenty of guys using 300 BLK for hogs and I don’t think FLA has any problem with night hunting them.
300BLK Factory Remington 115gr plinking ammo is $10.36 a box at Cheaper Than Dirt.
6.8spc Silver State 115gr is $16.18
Seems to me cost is relative to performance:
115gr vs 115gr @ 100yds:
Read more here:http://68forums.com/forums/showthread.php?31508-I-think-I-made-the-better-choice
Hogs (one page of thousands just look around a little): http://68forums.com/forums/showthread.php?17900-2011-Hunting-photo-s-thread&p=249713&viewfull=1#post249713
Not trying to argue, but the 6.8 and the 300blk are two totally different animals. All that I would say has already been said above. I will also add that short barreled suppressed use is where the 300 leaps above. The 6.8 has a longer range and does what it was designed for as well.
Now you have to decide…
You should get both of them, and then get a .204 a .25wssm a 6.5 a .450 Bushmaster a .458 SOCOM and a Beowoulf. Now you have MOST of the gaps covered. 
Really It doesn’t make a goddamn difference which one you get. One way you get a little more power/recoil the other a little less. One way you save a couple bucks on magazines. Either way the pigs die.
6.8 pro’s
A lot of factory hunting ammo available from Hornady and SAA, and Federal and Tula will be anouncing at the shot show 2013
Ballistically a better cartridge. The 300 BO opens at lower velocities because it is a slower bullet with a greater bullet drop
6.8 is about 80% of the performance of the 308 with a lot less recoil
300 BO Pro’s
Same mag and same bolt as the 5.56
I can’t speak to the retail off the shelf ammo available
I won’t bring in cheap plinkng ammo, since you already have 5.56
If you reload, then the hunting bullet variety will be similar
That is a weird thing to say.
From http://palmettostatearmory.com/index.php/firearms/rifles/stag-arms-6-8-ar-15-16-model-5.html
“This Model 5 uses the 6.8mm SPC, giving it 80% of the stopping power of the .308, more than the 6.5 Grendel, and only half the recoil in a standard AR package.”
If you want to shoot a 308 in a lighter package, a 6.8 would be a good choice,
If you want to shoot a 30/30 with an upgraded bullet selection and in a semi-automatic platform a 300 BO would be a good choice
Anytime someone writes or whispers 6.8 or 300 blackout the same thing happens. I’m not trying to get into any type of argument of any kind. The things you said are not so. If you want a .308 in a lighter package get a lighter .308 a 6.8 doesn’t fit the bill. if you want a 30-30 with upgraded bullets buy some LEVERevolution bullets. A 6.8 is in no way comparable to a .308 a .270 maybe. Half the recoil? this is all usless subjective info. I got one for you if you want a 6.8 with less than half the recoil and 80-90% the stopping power get a 5.56.
I don’t care what PSA is saying.