Ar 15 6.8 buffer/spring

[303 hunter]

When changing from 5.56 to 6.8 uppers,do you have to change to a heavier buffer or spring? I traded for a 6.8 upper with floorit76. This is my first 6.8. Let me know what to expect for this and any other issues you can think of. Thanks in advance. 303

 

[mokin]

You do not have to change buffers or springs. Depending on the gas system length you may want to. Some writers recommend this. I have a 16" barrel with a carbine length gas system and the rifle works fine even though it is probably a little over-gassed.There definitely seems to be a stronger recoil pulse and it is significantly louder than the 5.56. Other issues I have found is that ammunition costs twice as much but seems more satisfying to shoot.

After reading articles and internet forums for days while researching what parts to buy for my build I decided that for a range toy or huntung rifle, basically not a rifle capable of fully automatic fire, the "special parts" weren't really neccessary.

Go check out 6.8 forum and ar15.com for more information.

 

[68wj]

There is little way to know without shooting it. The 6.8 operates off the same pressures that the 5.56 operates from (more powder, but more bore diameter), but each barrel can have different characteristics. You are most likely fine with what you have.

Some 5.56 shooter swear by different springs and buffers too, so this is really no different.

 

[madcratebuilder]

I would start with your existing buffer/spring. The 6.8 barrels gas port is sized to give similar pressures to the bolt carrier. If you feel it's over gassed then try a heavier buffer. I wouldn't waste money on a aftermarket spring unless you have a very unusual build.

 

[Gtscotty]

Ive been thinking about this as well, I just got done putting together a 6.8 SPC II with an 18" barrel. I intend to run full power loads through this rifle, and as of right now it has a standard weight carbine buffer and spring. I guess I'll just have to see when I finally make it to the range.

I've seen charts showing under-gased/ over-gased in terms of where the ejected shell lands in relation to the rifle and shooter. Is this the only/best way to tell if a rifle is over or under gased?

 

[WVHunter1s1k]

14-16+" yeah, existing buffer/spring is fine with a mid-gas. You get into shorter barrels. It get's tricky from what I have read.



Oh, mags! 6.8 needs different mags.
ASCs/Stoners are fine up to 2.295 COAL. Except, with the 140gr SSA Berger ammo.
PRIs & C Product Defense(Reportedly) will handle it (2.3 COAL).
Barrett and D&H still use 2.6 COAL. Which is fine for standard ammo.

 

[madcratebuilder]

Ive been thinking about this as well, I just got done putting together a 6.8 SPC II with an 18" barrel. I intend to run full power loads through this rifle, and as of right now it has a standard weight carbine buffer and spring. I guess I'll just have to see when I finally make it to the range.

I've seen charts showing under-gased/ over-gased in terms of where the ejected shell lands in relation to the rifle and shooter. Is this the only/best way to tell if a rifle is over or under gased?

The ejection pattern chart is a guide only. If you feed ammo OK, bolt hold open works correctly, ejection pattern would be secondary. If it's not broke, don't fix it.