you may recall I printed a G19 frame in polymaker PA6-CF recently - I have been really excited by this material as the feel of the frame is really nice and it is supposed to be super strong etc,

6 rounds and the frame starts to show some problems around the locking block.  meanwhile the prior frame made from polymax PC continues to deliver without issue with approx 20 rounds down-range.  I was really hopefull for the PA6-CF but it seems it would need reinforcing to work.  and such reinforcing may be possible.  See below - locking block shoulder has deformed up meanwhile the locking block itself has rotated such that the front end has moved upwards

CF makes it stiffer but not stronger.

I might try the FMDA frame as it has extra material at the locking block especially above the top surface on a PY2A

Actually a couple of things in the FMDA (gray) vs PY2A (orange) - FMDA extends the locking block shoulder above the top, creating more material to stop the exact type of movement I saw, and also Uses the rear (top) locking block pin where the PY2A puts all the pressure on the lug, the FMDA extends it into the frame material as well through the pin.  Since i dont have FMDA parts kits in hand, I am going to add the FMDA features to my PY2A frame and retry in PA6 CF and see if we can make this work.

Did you bake the PA-6CF after printing?

yep.. did the annealing and then the water absorbing per the directions from Polymaker.  

Why didn't you choose a glass filled nylon?

Polymaker claims the CF has higher strength and impact resistance.

Anything with fiber is only strong in tension. Short fibers are not generally as strong as long fibers.

@bionicmonkey What were your print settings for the Nylon?  I've got a spool of PA6-GF but have yet to get it to print worth a damn.

So far, Priline PC(blend)-CF is my favorite filament for structural pieces

Hot end ; 290
Bed ; 35
Enclosed (mostly because its cold now and dont want sudden drafts)
Retraction 3mm @40 mm/s (i usually go 1mm at 35 but this PA is goopy)
Glue stick on glass bed - i get too much adhesion but live with it.
50mm/s speed
Hardened steel nozzle.  

One thing - when this roll was new it printed amazing beautiful prints.  Amazing.  I have my roll in a dry box while printing and while stored but even so its been a couple of weeks and now it prints like crap with blobs and stringing and i think the overall it suffered some absorbsion of water.

I also found my nozzle got gooped up with exterior crap after a while so it was worth replacing the nozzle for any major print.  

Thanks!  I'll give that a go once I replace my power supply

I did a bit of re-printing today and things did not go so well - def. water got into the roll and the result was really bad - lots of bubbly texture, the appearance of overextrusion, and inconsistent layer widths exaggerating layer lines.  also lots of strings/blobs.

When I first printed I did something uncharacteristic - I set the settings, and just dropped in a relatively big print right off the bat without any farting around with calibration cubes or test prints - nope, just boom, straight to a receiver.  this turned out to be a REALLY IMPORTANT GOOD THING.  that roll came off the line sealed and dry and was only going to be that way for so long, so get down to it.  I should have baked the roll after that, but didnt, and so the other lesson would be; break that seal when you are ready to use that stuff, or bake it before using because it is much more hygroscopic than anything i have ever worked with by like 10x.