My guns are a bit weak. I am lvl 12 still in the early middle (?) and my best guns are a slow hunting rifle, a weak service rifle and a 10 mm msg. I am trying to use AP-rounds rather then hollow-points but I still get the dreaded "red shield" every so often.
Stealth crits are not an option, I dont have the skillpoints to spare, and I save the stealth-boys for critical moments.
Would the "hand loader perk" help?
Do I HAVE to in vest in stealth?
Should I be-line in say explosives?

Gun was king i FO 3. Has that changed?

In regards to Hand Loader, I highly recommend it.

It gets you:

* 10mm JHP Hand Load
o x1.65 Damage
o x2 Target Damage Threshold

* .308 JSP Hand Load
o x1.5 Damage

* .357 Magnum JFP Hand Load
o x1.25 Damage
o -3 Target Damage Threshold
o x0.80 Spread

* .45-70 Gov SWC Hand Load
o x1.2 Damage
o -6 Target Damage Threshold
o x3 Gun CND

* .44 SWC Hand Load
o x1.20 Damage
o -6 Target Damage Threshold

* .50 MG Match Hand Load
o x1.15 Damage
o x0.65 Spread

More gun skill -> more damage. You can always get better guns too. Go to Boomers, do their quest, find Assault Carbine and Marksman Carbine...

How do people come to a conclusion that Marksman Carbine or All-American being great? They are semi-automatic, to utilize it's full potential you've got to keep clicking your mouse. Why wouldn't I spend that effort to make the shot count?