What parts do I need to change on a Standard AR-15 lower to mount a 6.8 SPC, 6.5 Grendel, or a 300 Blackout?
For the upper, do these use standard AR-15 parts except the barrel? If not, what other parts need to be changed?
THANKS!!
I know the 6.8spc and 6.5 use different bolts and mags as well. I want to say the blackout uses standard mags but I don’t know about bolts.
Correct. 6.5 and 6.8 use different bolts and mags. .300 Blackout is based on the 5.56 case, so it uses the same bolt and mag.
Will
300 only needs a new bbl. The mags and bolt are the same.
Will all of these use a standard AR-15 upper receiver?
Yes it will
Thanks. Now to decide which one to build!!
All three of the rounds look close in ballistics.
After looking at limited reloading info it looks like the 6.8SPC is the best hunting round.
6.5 Grendal will shoot a bit flatter.
300Blackout will be the most cost effective to shoot and would carry more energy at closer distances.
Are any of these considered more accurate than the other?
300 BLK is 30 round capacity. The others are less, but have better long-range ballistics.
I would pick 6.5 if you want to shoot very far, and 300 BLK if you want to shoot mostly not very far.
300 AAC BLACKOUT crosses the 1200 fps point at about 510 yards from a 16 inch barrel. I did shoot it at 600 with good results, but that is the outer limits.
When I had a 6.8 I used barrett 30 round 6.8 mags. They were pricey but were rock solid. One of the best built mags for an ar that I’ve seen. If they made them in 5.56 I’d pick them up.
Not going to try to convince anyone to go Grendel, just provide some data points. I think someone from AAC said it best: “If you think you need 300BLK you don’t want a Grendel, and vice versa”. (roughly paraphrased).
Point being: they are designed for two completely different purposes, with different end goals.
If you plan on suppressing, then 300BLK wins hands down. If all your shooting is under 100 yards, then you’ll never see the difference and you might as well go the cheapest route. (300BLK)
If you are interested in longer range work, there are several things in the Grendel design that lead it to be inherently accurate. Not magic, just basic things known to the accuracy guys for a long time. (cartridge shape, primer type, flash hole size, bullet design, etc)
We have seen that in our Grendels. They are quite accurate even with modest carbine builds.
Regarding energy & hunting, you have to look at retained energy at range. If all you care about is 0-100 yards, then they are all very close. The Grendel shines at longer ranges both in accuracy & retained energy.
From a cost perspective the advantage on builds is 300BLK, but only by about $100 (on average). Grendel barrels normally come with bolts. Right now you can get a quality rack grade grendel barrel & bolt for $212, and routinely excellent SS barrels can be had for $280-300 with bolt.
Mags for Grendel have been running $11-15. They are different, as are SPC. 300BLK would have the advantage for sure as it uses 5.56 mags.
You can get nicer 6.8 mags (barrett) while the Grendel is mainly a SS variant of Cprod mags. (With D&H coming online). I know people do not like Cprod, but within the last 2-3 years there have not been issues with Grendel mags, they either work or they don’t like any metal mag.
Ammo is about par, with Wolf (PPU) brass cased Grendel MPT around $12-13/box and it’s at least the quality of the basic RP loading for 300. Steel cased PPU is on track for this year based on multiple industry reports. Hornady premium grendel ammo is running about the same for all the mid-sized cartriges (Grendel, SPC, 7.62x39, etc). And it’s excellent as well. the 123g AMAX bullet was tuned for the grendel, and even though hornady does not position it for hunting many are using it with excellent results.
The one other Grendel advantage that swung me as a reloader is you can use 7.62x39 brass, it’s a simple fireform. This kept me shooting during the 08-09 scarcity’s as some excellent IMI brass was available when SPC & Grendel were unobtainium.
Again, just data points. If I were making that decision again, I’d probably go Grendel again. I think 300whisper/BLK definitely has some merit/interest, but for my goals Grendel fits better.
I have a couple of questions here:
Does anyone offer a 20 inch barrel for the 300 Blackout? If so how are the ballistics or, is this a waste. If I built up a 300 Blackout SBR with a ~10 inch barrel what would the effective Max range.
As I have read the replies here and on other sites I have moved away from the 6.8 to either the 6.5 Grendel or the 300 Blackout.
If I decide to shoot at a longer distance I will buy a match grade 5.56 24 inch barrel and re-barrel one of the existing uppers I already have.
I would like to use this upper/new weapon for HD and possibly as a Feral Hog gun. The 300 Blackout looks to be the mac daddy for a Suppressed, SBR shooting subsonic ammo.
We made some 20 inch barrels. The velocity keeps on going up, so it is not a waste. Still, I feel 16 inches is the sweet spot.
20 inches would be for supersonic ammo only - though handloads could be subsonic.
What is the effective max range for a 10 inch 300 Blackout shooting subsonic and supersonic ammo?
I am trying to work that out for a 16 inch upper and came up with 520 yards before the ammo drops down to 1200 fps (doppler radar). This is about 485 meters. But then again, I shot at 600 yards and hit the X ring, which was only 3 inches (1/2 MOA). So the accuracy held up to 600 yards/548 meters.
I don’t have 10 inch velocity data for this ammo. If I had to guess, I would say 400 yards.
Subsonic I would not plan on shooting past 200 yards.
Thank You. How much bullet drop did you have @ 600 Yards?
At this point I am leaning toward the 300BLK.
The BC worked out to 0.320 and the muzzle velocity was 2250 fps. So you can compute it from that.