AR build: Suggested caliber?

[Indy574]

I have both, the 6.8SPC and 5.56. I definately enjoy both rifles and wouldn't hesitate on recommending the 6.8. In fact it was my first AR, because I wanted more than a .22 caliber rifle and it fit the bill perfectly. Ammo can be found for around $16 (SSA) if you shop around.

 

[wilianknow]

I would and I am building a 6.8 it has 80% range and power of the 308. Good choice if you are going to reload. Look at the table of all the cal you might want to try.

 

[starbreather]

The blackout is a glorified 7.62x 39,but I still want one, go grendel. If I had the cash to build one that would be my choice.

 

[melensdad]

I would and I am building a 6.8 it has 80% range and power of the 308. Good choice if you are going to reload. Look at the table of all the cal you might want to try.

If you compare bullet energy then your comparison is invalid. There are some heavy loads that are both rare and expensive that perform pretty well but with that exception the reality is the 6.8 does NOT compare well to the 308. The 308 sets a standard that is very difficult for any small cartridge to live up to but I believe you may have fallen prey to misleading advertising, something that was very common to the claims about the 6.8 SPC.

Usingx standard bullet weights, at 100 yards, the 6.8 has only 75% of the terminal energy. At 200 yards it is right about 1100 ft.lbs. of energy but the 308 carries that much energy almost out to 500 yards. Not sure how that equals 80% of the 308???

 

[ryknoll3]

I only use it at the range. Like my 5.56 setup, but figure if I am building one may as well get a bigger round. Very interested in the 6.5 and 6.8 round.

What kind of ranges (distance) are you shooting? If it's only a range gun for 100-200 yards, I would definitely recommend the 300 Blackout. It's going to be a cheaper to shoot than the 6.8 or the 6.5., particularly once some of the overseas ammo mfg's start cranking them out. If you don't need the legs of the Grendel for longer range, I don't really see the point.

 

[melensdad]

What kind of ranges (distance) are you shooting? If it's only a range gun for 100-200 yards, I would definitely recommend the 300 Blackout. It's going to be a cheaper to shoot than the 6.8 or the 6.5., particularly once some of the overseas ammo mfg's start cranking them out. If you don't need the legs of the Grendel for longer range, I don't really see the point.

Of the 3 rounds you can look and the strengths and weaknesses of each. The 6.8 SPC and the 300 BLK are both shorter range rounds, topping out their effectiveness against game at about 200 yards (based on the commonly accepted 1000 ft/lbs of energy) while the Grendel pushes that out to 400 yards and/or it give much more knockdown power at shorter ranges. The 6.8 SPC and 300 BLK thrive with short barrels, the Grendel prefers barrels in the 18" range, so if short barrels are your thing the 6.8 SPC or 300 BLK are better choices. As for ammo prices, 6.8 is the most costly, Grendel in the middle, and 300 BLK is close to the lower priced Grendel ammo. Both 300 and Grendel have promises of foreign made lower cost ammo, neither has yet delivered that ammo. For hunting all 3 will work, but the Grendel will deliver more energy on target at every range so it gives you ethical choices for larger game. For prairie dogs or similar hunting, the 300 is clearly the wrong choice as it has limited range and the arc of a rainbow; a 6.8 SPC will work with lighter bullets, but a 6.5 Grendel with lighter bullets will be better. If you want to run a silencer then the 300 is clearly the best choice, the Grendel the worst.

 

[cartmanfan15]

I normally shoot at atterbury, but it would be nice to have a nice long range ar15 as well. Have a remington 700 in .308, but I would like an AR too in a larger round.

 

[Big Charlie]

45 acp would be sweet. Or better yet 10mm.

 

[ryknoll3]

I normally shoot at atterbury, but it would be nice to have a nice long range ar15 as well. Have a remington 700 in .308, but I would like an AR too in a larger round.

What distances are you looking to shoot, or hope to be able to shoot at when you say long range. I would definitely look at either the 300 BLK or Grendel.

 

[ZbornacSVT]

I don't think you'll be happy with the 6.8. Go with the 300 or 6.5 depending on your needs/wants, or go with both!!

28" 6.5G (first AR build) I really need a better pic of the rifle...

9.5" 300BLK SBR (most recent build)

Here is the .223/5.56 in comparison to the 6.5G:

 

[cartmanfan15]

wow. Nice. Are there any special parts you need to put in in regards to buffer tubes, new mags, etc for a 6.5 compared to the 5.56? Would like to keep some parts if I can to cut down on the new build cost.

 

[DarkRose]

I don't think you'll be happy with the 6.8. Go with the 300 or 6.5 depending on your needs/wants, or go with both!!

28" 6.5G (first AR build) I really need a better pic of the rifle...

Holy flying car, Batman! I thought my 26" was a long AR...

 

[melensdad]

wow. Nice. Are there any special parts you need to put in in regards to buffer tubes, new mags, etc for a 6.5 compared to the 5.56? Would like to keep some parts if I can to cut down on the new build cost.

The barrel, the bolt and the magazines are different.

I have done some testing of the magazines for the 6.5, the 6.8 and the 5.56 in terms of interchanging them and feeding different ammo out of each of them. The ONLY difference between a 6.5, a 6.8 and a mil-spec 5.56 magazine is the plastic follower. I have successfully fed the 'wrong' ammo out of each of these magazines. They are nearly interchangeable. The only time I had the OCCASIONAL issue was under rapid fire scenarios, but when firing controlled fire at the target range there were no real issues when I mixed one type of ammo in another type of magazine.

All my testing and interchanging was using mil-spec aluminum 5.56 magazines versus C-Products stainless steel magazines in 6.5 and 6.8.

Specifically for the Grendel, some folks have successfully used a standard 7.62x39 bolt, others have had issues with those and broken them over time. The head of the Grendel and the 7.62x39 Russian are very similar but the Grendel operates at a higher pressure, consequently Grendel bolts are slightly stronger to handle the extra pressures. Some people claim there is no difference in the bolt. I have only used Alexander Arms bolt assemblies in my guns so I can't speak with much authority about others.

 

[ZbornacSVT]

What he said.

While I do have some dedicated 6.5 mags, I have used my PMAGS in a pinch when I was an idiot and left my dedicated mags at home.

 

[cartmanfan15]

Not finding 6.5 barrels. Do you have to look somewhere specific? I have seen some 6.8 barrels on PSA, but not seeing much on 6.5. Also, anyone used the stainless steel ones? I know they are a decent amount more, but they look fantastic and seem like they would hold up longer. Also I like the shiny gleam it gives off.

 

[ZbornacSVT]

See if you can still find any of the SS Satern barrels. They will cost a bit more, but they are top notch. If you call them, they might still have something laying around. I know they were supposed to have them all gone last year due to licensing issues, but you never know..... With the round going SAAMI, it may not be an issue anymore.

 

[ZbornacSVT]

I actually have been wanting to do a mk12 mod0 clone using a spartan-ish barrel....

 

[cartmanfan15]

Found some for Alexander arms. They any good? Not familiar with them, but they have 16" stainless steel barrels for 195

 

[ZbornacSVT]

AA generally doesn't make there barrels/items. They developed the round, so they should be good to go. Never used any of their branded items specifically. I do know they used to use Satern for some of their in house builds.

 

[melensdad]

On of my Grendels has a Satern stainless barrel.

It shoots 1/2 MOA at 200 yards.