The Firestrike is, even when it isn't padded, a quiet weapon. Especially when you consider the fact that there's a feature which makes even an unpadded Firestrike very quiet.
Hold the trigger and pull back the primer as normal. Once it's pulled back fully, release the trigger. This makes no sound at all, and has no cost. At all.
There's seriously no reason why you shouldn't do this.
Firing (Way #1)
Firstly, prime your gun (if you haven't done so already). Hold the primer back lightly and shoot. The harder you pull, the quieter the gun will be - but the less power your shot will have. This shouldn't be a problem if you modify your ammunition, though - adding small, light springs to the bottom of your darts sacrifices a tiny bit of accuraccy for power. The more times the spring loops around the dart, the more accurraccy and less power it will have.
I'll go over it in more detail someday.
Don't count on it though.
[EDIT: Power is reduced for some blasters. Test this before you start fighting in a real game with your modded ammunition.]
Firing (Way #2)
DO NOT prime your shot. Instead, hold the trigger and pull back your primer. Do not pull it all the way back and release the trigger, though.
When you want to fire, release the primer and the trigger at the same time. No matter how hard you tug the primer, no matter the distance between the primer handle and the gun, the sound will be the same, although the sound will be less than the first one at the amount of power this way fires the dart at.
By the way, I just chose the Firestrike because it is the stealthiest blaster using a primer that I know of. Most blasters utilizing a primer will work with this method. Keyword is 'most' here.
EDIT: Of course, you can't prime silently or fire the second way with slam fire. I only just got my first slam-firing blaster today (Disruptor), and when it relies on priming with the trigger held down, it's pretty useless.
Sorry, Solid Rambo.
And for you zambie mainers out there; how would you deal with the hunters being hunted - but the hunters not knowing where the danger is coming from?