AR 6.8 SPC Compatability

[Rod4277]

Probably a dumb question here! I have a Left hand AR-15 5.56 built from various components including a left hand Stag upper. This was my first build and I'm still learning. The lower is marked "multi" caliber. I'm thinking about getting or building a left hand 6.8 SPC. Is there any modification to the lower that should be considered? All constructive advice welcome. All comments regarding the 6.8 mm SPC also welcome too.

...... Rod

 

[Float Pilot]

I have been playing around with the 6.8mm SPC for a few years.
All you need are the magazines and another upper.
My Stag 6.8 was improved very much by the addition of M4 style feed ramps.

 

[mokin]

I've got a 6.8 SPC with a 16" Stag barrel and M-4 feedramps are a definite improvement in feeding. Great little rifle. The boom really suprises people who expect a little 5.56 crack.

 

[suzukisam]

Bolt, mags, and barrel..only difference!

 

[68wj]

Stag makes a great lefty 6.8 (a great righty too). However, there has been much discussion on the M4 feed ramps. Stag maintains that they are not neccessary, and many users have not had problems. On the other hand, many users have and the problems have been solved by the lengthening of the ramps.

The problem is the 6.8 cartridge is fatter than its little nephew the 5.56, and thus sits slightly lower in the magazine (.025" IIRC). Depending on magazine condition or ammo type, the point of the bullet may connect with the receiver/barrel extention incorrectly and cause a failure to feed.

Were it not for the ramps, Stag would be one of the best (for the money) options in a 6.8 upper, and the only left handed option. Of course, if you get one, yours may run just fine and would make a great rifle. If it doesn't, M4 ramps are an easy DIY job or can be done cheaply at most any gunsmith.

To directly answer your question, no, nothing needs to be done to the lower.

 

[suzukisam]

Adding feed ramps to a receiver takes about 15 seconds, the problem is whether the barrel extension has them or not.. I have had several feed ramp barrels and just added the ramps to a non feedramp receiver

 

[Rod4277]

Thanks!

Thanks to all of you that replied.

Have a great day!

......... Rod

 

[Rod4277]

I took the plung today!

Okay I made my mind up today and ordered a complete Stag Arms upper model 5HL today that's the south paw version of the 6.8 mm SPC. I already have a model 3HL 5.56 NATO paired up with a custom built lower and I'm very happy with it. I feel that STAG is the best choice for left-hand shooters.

 

[brian923]

Your gonna love the 6.8. Ive worked up a couple handloads that are sub MOA at 100 yards. The only factory ammo i shot is the remington 115 otm's and they shoot great as well. Let us know how yiou do, and maybe a pic??

 

[1stmarine]

No. The same lower for all AR15 calibers. You only need an upper with new bolt and in this case new magazines.
Some require a new buffer spring and weights to adjust the timing.
If you want to reuse the same bolt, magazines, etc... there are other calibers that are also very good.
Cheers.

 

[Rod4277]

Picture

Thanks Brian! I do xome handloading myself and would be interested, I'm attaching a picture taken with the Stag Arms 3HL and will take some more when I receice the 5.8 SPC model 5HL.

 

[68wj]

Thanks Brian! I do xome handloading myself and would be interested, I'm attaching a picture taken with the Stag Arms 3HL and will take some more when I receice the 5.8 SPC model 5HL.

Enjoy! Great that you handload too as you can really wring out the performance. Most factory loads will be on the slow side as they are made for the old chamber (will still function fine in your correct chamber though). SSA and Wilson Combat both make SPCII specific ammo, but as I am sure you already know, handloading will allow you to really dial into your new rifles potential.