vapour, once created, is only potent for so long... In my experience, the quicker you get the smoke into your lungs, the better. That being said, filling the chamber is NOT in your best interest, it's better to just create a constant stream straight into your lungs.
Also, some brown marks will typically show up, but looking at the pictures you showed, I would say there is just a BIT too much markings. Try heating it a bit less... You want to heat it just enough to keep it liquid. That being said, it doesn't look too bad.
The fact that pipes made for meth typically dont have a chamber, or a very small chamber would also lead me to believe meth is best inhaled directly, and your hits arent meant to be built up like with marijuana
. One reason I'm pretty sure big hits are built up in the chamber with marijuana in the first place is to let the smoke cool down a bit before inhaling. With meth, the smoke/vapour isn't hot, or noticeable so therefore there is no need to cool it down.
At the end of the day, as long as your not keeping the smoke in the chamber for a ridiculous amount of time, it's not going to make a big difference.
And one more thing... Light bulbs can be pretty effective,you should really try find a pipe. Perhaps there really aren't any available in your area, but sometimes you'd be surprised. Most places that sell them don't keep them out on display, you have to ask the cashier - at least in Canada anyway... But their out there you just gotta know where to look. Ask your dealer maybe?
Its just that, the material used to make actual pipes is a much better insulator than a lightbulb, and therefore your meth will melt a lot quicker, and crack
back much sooner with a pipe. Plus it's just better all around. Resin builds up down the stem nice and quickly too in a glass pipe as opposed to the straw or pen casing or w/e it is that you use as a stem.
Well, good luck! Happy tweaking.