Buffer Question

[NHM90]

I bought a pinned M4 style stock from a friend of mine. He kept the buffer and spring for another stock that he had. I now need to buy a buffer and spring to finish my build, but I don't know if I need a CAR length or A2 length buffer and spring? My RRA upper arrived today and the lower parts kit will be here soon, so this is the final piece in the puzzle.

(This will be my first AR build, so I am unfamiliar with a few aspects...and my friend is now away at basic.)

Thanks.

[oclvtrek]

You'll want an A2 buffer spring since your buffer tube is full length and not a carbine tube. If you look at the back of the buttstock and see the end of the tube you'll see it runs the entire length. of the buttstock.

[Dano523]

Define pinned.

There are Car stocks that start off as telescoping stocks, that some one has installed a pin, then there are fixed stocks that the receiver extension extends all the way back to the end of the butt stock (butt stock, fully extended).

If you back of the receiver extension (tube) is flush with the back of the butt stock, then you need a full-length buffer and spring. If there is a void (open hole) between the back of the butt stock, and the receiver extension (like the tube is short) then you need a Car buffer.

Also, if this butt stock started its life out as a telescoping stock, then pinned, it's not approved as a fix design by the BATF, and should be removed and replaced with an approved fixed style unit.