Gear for climbing St Helens is all non-technical. I guess hiking poles and knowing how to use a rope are about as high tech as it gets.
Rope is for emergency only. Poles help with ascending / descending the loose sand (Scree).
Most important gear, and why so many failed that day, is Gortex or other breathable waterproof pant/coat. I use a Mt Hardware Exposure II parka. I don't like wet/cold, and at 45 I'm smart enough to prepare.
It takes 6-8 round trip with about 4.5 up for people in decent shape. I've seen fat-asses do it. It just takes determination; especially when your heart is beating out the top of your head at 7500' (Summit is in sight at this point and is at 8100').
Everything you need to know is here
Climbing Mt St HelensI take the 10 essentials in a medium size day pack (Google 10-esentials), 2 quarts of water..more it's hot and sunny. Extra food. Extra polypropylene clothes. Cell phone, GPS (needed it this trip with the fog on the way down).
Hope this helps. And oh, no gun. I thought about my SW Air Weight but was unsure of WA laws in this type of forest...I had a big knife though...