Gunboards Forums banner
1 - 10 of 10 Posts

·
Registered
Joined
·
1,898 Posts
Discussion Starter · #1 ·
This should be an easy question for someone in the know. I'm building an AR but I don't want another 5.56. I'm considering a 6.5 Grendel or a 6.8 SPC for starters and I need to know if the bolt carriers and barrels work in a standard AR upper or if there are other differences such as ejection port sizes specific to those upper receivers.
I saw a VLTOR MUR receiver for an attractive price (in 5.56) but I don't want to get something I can't use
 

·
Registered
Joined
·
9 Posts
I don’t know much on this but here’s how it was explained to me when I asked my friend about his 50

The AR conversions to larger cal. use nothing longer than a 5.56 - 2.23 round … the mag well dimension is the limiting factor.
But I didn’t ask about things exiting being an issue
 

·
Registered
Joined
·
6,861 Posts
6.5 and 6.8 uses it's own bolt and mag, the carrier and receivers (upper and lower) are the same as 5.56.

the only different caliber that uses the same 5.56 bolt, receivers and mag is the 300 WHISPER or BLACKOUT, it's just a different barrel


but if you're the kind of guy that thinks 5.56 ammo is pricey, 300 WHISPER or BLACKOUT is far more expensive, like 30 some bucks for a 20 round box. which isn't your 'plinkering" ammo. folks that go with the 300 mostly do it for hunting
 

·
Gold Bullet Member
Joined
·
396 Posts
There is the 6x45 round/chambering which is aka 6mm/223. For it the brass is even the same as .223 except for expanding the neck to .243.
For 6x45 and .300 BO it makes sense to be a reloader. Components are relatively easy to come by.
 

·
Gold Bullet Member
Joined
·
4,569 Posts
6.5 and 6.8 will work on the lower 5.56, but I don't recommend to get 80% on this project to shoot 6.8.
 

·
Gold Bullet Member
Joined
·
4,569 Posts

·
Platinum Bullet Member
Joined
·
59,093 Posts
There is the 6x45 round/chambering which is aka 6mm/223. For it the brass is even the same as .223 except for expanding the neck to .243.
For 6x45 and .300 BO it makes sense to be a reloader. Components are relatively easy to come by.
i have a 6x45,

all is the same except the barrel,

i painted a red band on the handguards to help me tell the difference,

shoot well too, it has a very early (80's) SGW barrel on it
 

·
Gold Bullet member
Joined
·
1,777 Posts
I use a 6.5 Grendel and as far as I know the only difference in the Grendel and a "normal" 5.56 caliber weapon are the bolt, barrel and flashhider / muzzle brake. All other weapon components are same same.
 

·
Silver Bullet member
Joined
·
53,001 Posts
I have a Rock River A4 carbine reciever marked 6.8.
..It came with another RR 223 upper ...
sold / took off the 6.8..upper that came on it...
Got worried later that I had made a mistake deciding to keep the 223....
Everyone here said it will work without a hitch..I still haven't shot it
 

·
Platinum Bullet member
Joined
·
3,998 Posts
My 7.62x25mm DI build uses a FN M16 bolt that is opened slightly for the base diameter change. The gas port is also about 3.5" ahead of the chamber with a short tube. Outstanding reliability and very fun to shoot, but dirty as heck.
 
1 - 10 of 10 Posts
Top