Cav-ARMs lower hunting rifle build--Anyone speaks AR15-ese?

[doofus47]

I love a new DIY rifle project. So I picked up a Cav-Arms lower and have a lower kit and how-to DVD on the way from Brnnnnlls. That part will take care of itself sooner or later. It's my first build, I"m not going to rush it.

But I saw this on the CA lower instruction sheet:
takes carbine buffer and carbine buffer spring.

Whoa! I was hoping to put an 18 or 20 inch barrel on this and use it for a lightweight hunting rifle in 6.8 or 6.5.
Am I stuck using only 16" barrels? Not that there is anything wrong with that, but that wasn't my goal. Is my rifle pre-scuttled b/c I bought the wrong lower?

No such thing as Too-much-info. Feel free to chime in with any AR15 hunting rifle stories if they seem related.

(Please don't start a 6.8/6.5 debate; I like them both for different reasons and I will probably own both uppers at some point.)

 

[thesheepdog]

....Demigod.....Bartholomew....y'all handle this one.

I dont' have much experience with "which" buffer tube allows for "which" barrel.

 

[bedlamite]

You can put a 20" barrel on it, the carbine spring is stiffer than the rifle spring and will work fine with a rifle length gas system. However, with a Cav Arms lower I'd keep the rest of the gun as light as possible, which means a 16" lightweight profile barrel. Longer barrels can help a 6.5 but are not really necessary with a 6.8. I've even considered getting a stamp and a 12" barrel for mine.

 

[jmorris]

No, you can use any barrel length you just need the carbine buffer and carbine buffer spring. I did have to modify the trigger groups when I put together my cav lowers. They also feel awkward with 20” barrels because they are so front heavy. Despite being plastic they hold up well I have ran one of mine quite a bit with a 458 socom upper and it’s still tight.

 

[demigod]

You'll have to experiment with what buffer works best for your specific barrel/gas port... I'd probably start with an H or an H2.

I shot a class with Russell from CavArms. He used to run 20 inch rifle uppers on his guns, so it shouldn't be a problem.

 

[Zak Smith]

As others have said, there is no interrelationship between receiver extension tube type vs. upper configuration. As long as you are using a rifle receiver extension tube, rifle spring, and rifle buffer - or a carbine receiver extension tube, carbine spring, and carbine buffer, you are fine. Just don't mix lower parts types because you will probably damage the lower or other parts if you fire it.

Here's my 17" RLGS 3-Gun upper on my Cav lower as setup for Trooper Class.

 

[Technosavant]

Rifle vs. carbine receiver extensions/buffer tubes (two names, same part), springs, and buffers refer to the length of the extension/tube, NOT the barrel. Carbine buffer tubes are shorter, meaning the buffer needs to be heavier and the spring a bit stronger.

It's just a matter of buying a different part for that spot; as said, it has nothing to do with the upper you choose. Generally I'd recommend a heavier buffer as your gas system gets shorter, but even that isn't really a huge deal.

 

[sonrider657]

You can run a 20" barrel if you want but a lightweight 16" barrel will balance much better and exploit the advantage of the lightweight Cav Arms MkII Lower.

Here is my custom build that is only 5 lb. 1 oz. (without magazine).

 

[doofus47]

Thanks for the help, guys. I feel much better now.
The AR codetalker language has me doing a lot of googling.
Obviously, it's my first AR build.
The only way to get to know your rifle from bottom to top is to start at the bottom....

 

[demigod]

Yeah... sorry about the "code talk"... you'll be speaking it fluently in very short order.