What does the letter after damage mean?

By Rhubarb, in Deathwatch Rules Questions

What does the letter after the damage rating of the weapons in Table 5-5 mean? Say for example the Bolt Pistol reads 2d10+5 X or the Meltagun is 2d10 + 8 E. The weapon special qualities list seems to indicate that the X for the Bolt Pistol could stand for Blast, Felling or Devastating?

I'm certain this is a really noob question, but I just can't seem to find an explanation anywhere in the armoury chapter, and I'd like to be running this game tomorrow!

I believe that indicates the damage type. I for Impact, E for Energy, R for Rending, X for Explosive.

Thanks! I was confused since that isn't explained until 100 pages later in the Combat rules.