There have been several posts in the past devoted to string spacing, but here's one of mine that you may find helpful...
http://steelguitarforum.com/Forum2/HTML/002684.html

I'm sure if you do a forum search you'll find more than you'll ever want to read on the subject, but basically, you'll find as much variation between guitars on string spacing as there are different tunings! If you find that frustrating, you're not alone my friend. For what it's worth, here's my two cents:

Tranditionally, non-pedal guitars had a wider string spacing to accommodate slant bar work. Then pedal guitars hit the scene, and pedals and knee levers took the slant out of slanting (although you'll still find pedal players who slant the bar...typically those who started out on non-pedal). Also at this time, more strings were added to the guitar neck, which naturally caused the space in between those strings to narrow.

I prefer atleast a minimum of 3/8 (or 6/16) of an inch spacing between each string at the bridge. Anything tighter and my picks get caught up in the strings.

As for the nut, usually anywhere from 5/16 to 6/16 is standard. If your guitar is more toward the 6/16 (or 3/8) end, you'll probably find adjacent string slants at the lower frets easier to obtain and keep in tune. I don't mind the 5/16 spacing at the nut, except for this kind of situation, with E as string 1, and C# as string 2:

string 1: 5 4 3 2
string 2: 5 4 3 1

The bar has to be at a very severe angle to get that slant even close to being in tune. Usually a little vibrato helps.

What can be really frustrating, is that a few of my guitars have a slightly different spacing between each string! I can see where previous owners grooved their own little slits (slots?) for the strings to sit in, and must not have used a ruler to get it accurate. I've also seen it not uncommon for guitar makers to have a little bit wider space between the 3rd and 4th string (on a 6 string) for some reason...I guess it's due to how the tuners are placed.

Anyway, for all intents and purposes, you can't go wrong with 3/8, IMHO.

[This message was edited by Jeff Strouse on 10 August 2002 at 04:22 PM.]