been working with ar's for some time. works most of the time they work.  here's a new one put a rifle together. got a good deal on an a1 stock tube buffer the whole works. put it all together and the bolt does'nt travel all the way back it bottoms in the buffer tube. my question is this. is there difference betwen an a1 and an a2 setup. or do you think  the problem is with the spring. stuck a car buffer in and it went all the way back. thanks and excuse the spelling.

If I'm not mistaken the A1 stocks are 5/8" shorter than the A2.

Check to see if there's an obstruction in the tube.

Is the buffer retaining pin getting in the way?