Overall Best filament

LTD69

I recently purchased a X2D from Bamboo Labs. Im about to print the V4.8 lower but want to get everyone's take on filament. Ive read that PA6-GF is best as this is basically what Glock uses for its lowers, but Ive also heard thats its not and to go with CF filled instead or even not to use PA6 at all. Money isnt a concern I'm more concerned in what is the best for performance (strength, longevity, ect )

If using PA6-CF would you recommend a .4 nozzle with .16 layers or .6 at either .16 or .20.
I will be using a second filament for supports. I planned on using PLA but due temperature differences ive found out I cant. I thought the second extruder heated to its own temperature but it seems not. That being said would PETG be the best support filament?

Sesame

Congrats on your new X2D, I am in the same boat of wanting to utilize the dual nozzle set up for supports.
I’m currently trying out (all Bambu) PAHT-CF on .6; with ASA for supports. I have plans to try PPA-CF if my current prints don’t meet expectation; but have previously been very happy with PET-CF with ASA supports.

While I would advise against GF in PA6, it is still a great material if you understand the risk of hydration and moisture and are confident in your filament dryers and environment. I have the Bambu AMS HT, and I can get humidity down to 3% and have had amazing layer adhesion with fiber filled filaments.

I personally would recommend carbon fiber. PA6-CF out performs Glass fiber in almost every metric according to internal testing-

https://portal.bblmw.com/filament/filament-guide/250123/filament-guide-en.pdf

For support material- ASA/ABS is the recommended; but I have found PETG to be reliable for support interface or base+interface usage.
I have found better success with ASA supports for finish quality and higher quality details; but I have more difficulty fine tuning support settings for best results.

Layer lines- if you use Bambu- use recommended quality; but I always adjust temp, flow rate, and acceleration to error on the side of a cautious/slower print. .18 or .20 would be best on a .6mm. I highly advise against a .4 nozzle for filled filament; its very risky but it does not guarantee a catastrophic failure.

Tl;dr
If money is no object, run PPA-CF with a AMS HT with a diamond back .6 mm nozzle; but there is no “correct” settings- pa6-gf is fine; but carbon fiber has non-negligible advantages.