I'm a felon, so maybe muzzleloader (although black powder burns too slow, so there's a high chance of missing something). Suicide experts at ED needed.
As EDF's unofficial resident armorer, I can assure you black powder does not "burn slow."
Black powder is catagorized as an explosive. It combusts.
Modern gunpower is designed to burn in a controlled fashion and classified as a propellant.
To the naked eye and pedo-retards like you the rate of burn is indistinguishable. However, the forces in play are very different.
Black powder pressures come to a massive rapid peak and then as quickly recede as the projectile travels down the barrel due to the "expansion of the combustion chamber," and most importantly all of the powder that has been ignited has been consumed. The amount of force diminishes as the bullet/ball travels down the barrel, and doing so results in a typical maximum projectile speed of just supersonic. Modern firearms use the supersonic speed of the projectile to compensate for far less bullet mass.
Which is why BP firearms typically have heavier bullets and generally of larger caliber.
I'll save you from the terminal ballistics and the calculations involved, because you wouldn't understand. However, our resident engineer
@Maysam could happily explain why the reduction of fixed explosive force happens in an expanding volume. (LOL don't say I don't love ya -have fun :3 )
Propellant ignights and the pressure is designed to uniform as the bullet travels down the barrel. The powder travels down the barrel and ignites to maintain constant pressure.
Your jellyfish brain is misconstruing is the hebrewood portrayal of black powder firearms; that upon pulling the trigger, there is this absurd 1-3 second delay between the trigger is pulled and the firing of the rifle/pistol. I assure you it's almost instantaneous, just like a modern firearm, so you don't have to worry about getting cold feet for righteously removing yourself, yet another pedophile, from the face of the Earth.
However, the end result is messy and takes tow major things you don't have -- balls, and commitment.
In your case, since you are obviously a coward (ie targeting children for sexual gratification) you would want something as painless and easy as possible. The best solution would be a heroin overdose. People I've known who were H addicted and have overdosed, said it was a warm feeling and they just drifted off into a deep sleep. The foaming of the mouth and convulsions, and all the other hebrewood bullshit, while that does happen in many cases, the OD'er is completely unconscious at that time, and they said they were completely unaware of it.
Any gas other than oxygen would work. All you have to do is create a situation where you are getting less than 21% oxygen, and a feeling of drowsyness will occur and ultimately render you unconscious. While unconscious, it the situation is prolonged, brain damage can occur resulting in coma or death. The popular misconception of you having no worry since you have very little intelligence is completely incorrect. Your intelligence doesn't stave off biological demands or prolong biological function - more Hebrewood myths.
However, it doesn't have to be an expensive gas like argon. It can just be your foul exhale - C02. O2 at 19% can easily render you unconscious. But to guarantee death an O2 percentage would have to be sub 10%.
If you choose to gas yourself to death, the best and most available and inexpensive would be C0, carbon monoxide. I won't get into the chemistry and biology of why red blood cells cannot easily shed this molecule. However, using this gas as your method of cleansing yourself from the world, it would require far less CO to deprive you of O2. The effects of inhaling C0 are cumulative and permanent for the duration of the blood cell's life - a maximum of 7 days.
Please livefeed of the process you choose, so we may create the proper internet shrine to your greatest life achievement.