6mm /WOA & 6mm/6.8 SPC

[relictrader]

Recently I hear Carl shot a 798 at a match in Delaware shooting a different AR with a different cartridge,i.e. a 6mm/6.8 SPC with around 33-34 gr water capacity).

Can some explain these two Cartages to a NEWBIE?

 

[rayjay]

The 6.8 SPC is based on the 30 Remington case necked down to .277 [ and shortened to the AR15 mag length ]. The 30 Rem case head is .421 [ I think, CRS ] while the 223 case head is .378 and the 7.62x29 / 220 Russian / 6mmPPC / et al have a .443? [ CRS again ]. The .421 case head leaves a bit more metal in the bolt of the AR making it much stronger.

Neck the 6.8 down to 6mm/.243" and you have a cartridge that approximates the 6mmPPC while allowing a stronger bolt in the AR . The selection of match quality 6mm bullets is also much better than for the .277" bore size [ same as .270 Winchester ].

 

[relictrader]

THanksRajay,

I have wondered why with a few more horses needed to push the 105gr out to 600yds,...WHY not keep it simple and save on brass
cost by necking 6.8 down to 6mm and loading it with seating die.
The future may be short for 6.8,and if so cases will be a problem.
Lots of people are scrambling in every direction on cartage designs and forgeting about the shooter's budget.
Gary

 

[constructor]

2950fps from a .277 90gr TNT out of an 18" barrel.
may be able to get 3100 out of a 26" 6mmWOA,6mm/SPC) with the 95 Sierra. Holliger has the reamer.

 

[rcw3]

The 6.8 SPC is based on the 30 Remington case necked down to .277 [ and shortened to the AR15 mag length ]. The 30 Rem case head is .421 [ I think, CRS ] while the 223 case head is .378 and the 7.62x29 / 220 Russian / 6mmPPC / et al have a .443? [ CRS again ]. The .421 case head leaves a bit more metal in the bolt of the AR making it much stronger.

Neck the 6.8 down to 6mm/.243" and you have a cartridge that approximates the 6mmPPC while allowing a stronger bolt in the AR . The selection of match quality 6mm bullets is also much better than for the .277" bore size [ same as .270 Winchester ].

rayjay

I don't understand your point regarding bolt strength. All I can say is the 6mmAR and the 6mmAR Turbo use bolts with the same bolt face as the 6mm PPC and we have not had strength issues with bolts despite many uppers out there. We're pushing the 105-108 gr bullets up to 2900 fps out of the Turbo so I think we would see a problem if there was one.

Robert
www.6mmAR.com