Wild guess: friction and a lot of tension.

I suppose it depends on WHAT gun you're talking about, but in terms of the 1911 and others....


If it were to slip off, where would it have to go???

the guide rod is not connected to the barrel..... the muzzle end sits in a channel or tube..... the locking block end becomes captured by the take down lug ..... you feel the spring compressing as you make the alignment.... the lug is inserted or flipped and now the guide rod/recoil spring is captured by the limited slide travel..... does this make sense?

yep..thanks for the explanation.

as pointed out by vamarine..... this varies depending on the gun.... but my description is based on the most common beretta/taurus/sig/cz/tz styles and in no way encompasses all brands, models, styles or variations.....

here is a link to show how the various parts of the 1911 work together, some nice animations here.... notice how the barrel moves by the link.... not a cam or lugs like the new browning based designs

http://www.m1911.org/1911desc.htm

In my Glock the guide rod only rests against the notch in the barrel during assembly. The fact that it isn't perfectly in the half moon notch when I take it back apart means nothing. The notch is only there to position and hold the rod and spring until reassembly. After that it rests against the frame.