I was removing my receiver end plate for the first time and didn't do it quite right.  The detent spring for the pivot pin got caught between the receiver and the end plate when I was twisting the buffer tube and I mangled the end part of the spring.  I had to break that portion off - it was only the first 4 or 5 of those tiny little coils.  The end result is that the pivot pin still stays in, but I can tell it doesn't have the tension that it once had.

Is there any urgent need for me to replace this spring?  (I.e., before I take it out shooting)?

Urgent, no but it should be replaced.



Just throw one on the next order. Maybe buying a extro LPK might be a good idea.





If you dont plan on fixing it, you always can add a piece of wire/coat hanger to the back end to make up the space



or better yet tap the hole 4-40 and add a set screw since you already have the spring cut, a la quarterbore mod

Sounds like you are halfway here:

http://www.ar15.com/forums/t_3_118/395777_Simple_fix_for_the_rear_takedown_detent_spring_blues____.html

You can use a spring from a BIC lighter.
Until you get a replacement

I used a spring from an old zippo lighter I had, works great, just the right size.

This