AR-15 buffer length?

[Keane]

Hi all-
I am in the process of building my first AR. I started with the Cav-Arms Mk-2 lower.

I just got an upper in (a cheap gunbroker 16" upper, no idea of the brand), which came with a bolt and charging handle.

However, When I assemble it, the bolt doesn't go back all the way! It only moves about 3 inches or so, not enough to even clear the chamber.

When I pulled the upper and lower apart, I found that the buffer doesn't seem to go deep enough into the stock. What length is this buffer supposed to be? The one I have, is nearly 6" long, and even without the spring, doesn't seem to go back all the way.

I got the buffer from the previous owner of the lower, but I don't know if you can buy these in different lengths.

Am I doing something wrong?

Edit: After doing some additional research, it turns out the person I bought the lower from, included the wrong buffer/spring. Thanks for your time...

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[NoAim]

Hi all-
I am in the process of building my first AR. I started with the Cav-Arms Mk-2 lower.

I just got an upper in (a cheap gunbroker 16" upper, no idea of the brand), which came with a bolt and charging handle.

However, When I assemble it, the bolt doesn't go back all the way! It only moves about 3 inches or so, not enough to even clear the chamber.

When I pulled the upper and lower apart, I found that the buffer doesn't seem to go deep enough into the stock. What length is this buffer supposed to be? The one I have, is nearly 6" long, and even without the spring, doesn't seem to go back all the way.

I got the buffer from the previous owner of the lower, but I don't know if you can buy these in different lengths.

Am I doing something wrong?

Edit: After doing some additional research, it turns out the person I bought the lower from, included the wrong buffer/spring. Thanks for your time...

That's correct. Even though it's an A1 length stock, it uses a carbine buffer.