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Right now PPA-CF seems to be the sweet spot for price vs. performance vs. printability.
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Annealing results in more uniform crystalization which generally reduces impact strength. If your salt annealed parts showed higher impact strength, that's an indication that the annealing was actually unsuccessful.
It would help if you define what you mean by "higher caliber". The French AA-52 was a lever delayed 7.62x51 and the Soviet Garanin was a lever delayed 7.62x54R. The French MAC-58 was a lever delayed 50 BMG! And of course the H&K G3 in 7.62x51 was a roller-delayed blowback system.
If you do the math you'll see delayed blowback is every bit as viable as gas systems for pretty much any caliber. Gas systems are more prevalent now simply because they're cheaper to produce, have higher tolerance for harsh environments, and tend to have longer service life, but neither of those are really priorities for privately manufactured firearms for civilian use.
Just my $0.02, but I don't think polymer FDM technology will ever be suitable for gas system components. So if you go down that path, you're looking at sophisticated DIY metal parts that it will put the design out of reach of most people. ECM may be viable for some of these parts, but there's a pretty big skill gap between cutting a barrel tube to length (where actual length doesn't matter at all to the process), and cutting bar stock to the rough sizes and shapes needed to fit ECM jigs. Take a look at the Rogue/Rebel 9mm bolt instructions for an example of a steel assembly that's pretty close to the limit of DIY-ability.
IMHO, the key to handling more powerful cartridges is figuring out how to do a delayed blowback system that is easy to DIY. I'd suggest doing some research into lever-delayed systems (Forgotten Weapons has a good intro here: https://youtu.be/utv6LK6CxJI ) and thinking about how existing DIY bolt designs might be adapted to utilize that. I don't know if it's practical to get all the way to full-power rifle cartridges with a lever-delay system, but it definitely has potential for intermediate cartridges like 5.56x45 or 7.62x39.
Lots of possible causes for z-banding. This article does a pretty good job of breaking them down: https://all3dp.com/2/z-banding-z-wobble-fix/
At 5% moisture content (about as high as you'll get unless the part is literally submerged), Polymaker PA6-CF still has 50% more tensile strength and 165% more impact strength than their PLA Pro. Layer adhesion is weaker (63%) and stiffness is slightly lower (85%). Most designs that will work in PLA+/PLA Pro will work fine in moisture conditioned PA6-CF.
Coatings like Cerakote can slow moisture absorption, but when you consider the cost and effort, you're far better off just printing in something like PPA-CF.
No. Tensile strength of 7051 aluminum is still roughly 5X that of PPA-CF and even the much weaker 6061-T6 is still 3X stronger. Stoner would have had to over-design the lower by 3 - 5X (despite having weight reduction as a major goal) for an all-polymer MIL-SPEC lower to be viable (even with injection molding).
Nicely done! I've been recommending the Hitchhiker to newcomers for a while now. Arguably safer than the Harlot as a 1st build just by virtue of having your digits farther away from the explodey bits.
How is the recoil on the 5.7 MAC uppers? I built a DB9, but hated the 9mm MAC 11 action (way too harsh). I've since converted it to 22LR which I love, but I've been really curious about the 5.7.
For NFA items I've been using the MAF heat set serial number tags (https://maf-arms.com/product/heat-set-serial-number-tag/). I add the recess as a negative part in the slicer (there's a link to my STL file on MAF's product page). Then I drop the plate in with a drop of super-glue and use a soldering iron to melt over the posts to further lock it in.
If your FFL is just doing the engraving of a serial number you picked/registered, the MAF plates are cheaper/easier. Unfortunately, if your FFL is assigning a serial as part of a 4473 transfer, they probably won't give you the serial in advance. The heat-set approach may still be viable, but you'll have to source your own blank plate(s).
Advice:
- Test and calibration prints are the difference between good and great prints. I probably printed 50 little test objects in the process of learning/tuning support settings alone. The Ellis Print Tuning Guide is a good (albeit a little advanced) resource: https://ellis3dp.com/Print-Tuning-Guide/ . I say "advanced" because not everything in there is applicable to all printers so you'll have to put a little effort into learning what to use and what to ignore.
- Start with a reputable brand of PLA+ or PLA Pro. Skip the "artistic" filaments, and don't bother with the engineering materials (nylons, etc.) until you have working builds in PLA+/Pro. I have plenty of experience with other materials and I still use PLA+ for the first time I print any design. Once I have 1000 rounds through something and I'm sure I want to keep it long-term, I might reprint in something more advanced. But I've thrown away several kg of parts over the last couple years because the print quality didn't meet my standards, the design had problems, there were aspects I wanted to change/customize, or it just wasn't that enjoyable to shoot. It hurts to trash $60+/kg parts.
- Learn some modeling. Blender for customizing STL files, your choice of CAD programs for design or major modifications. It's really not that hard to learn (just different) and there are lots of good tutorials and even interactive teaching sessions. Customizing, not just building, is how you truly take advantage of the "open source" aspect of FOSSCAD.
There's no such thing :) PAHT is a marketing department invention, not an actual polymer. It's usually either PA12 or PPA, but you need to check with the manufacturer to find out what you're really getting.
If you're annealing at the correct temperature, there's no need to pack PPA-CF in salt. The annealing temperature is well below the un-annealed heat deflection temperature so you shouldn't experience any warping or distortion.
In 2025 there is almost no reason to manually adjust all the speeds in your print profile. If you want to slow things down, go to your filament settings and under "Volumetric speed limitation" there's a field for "Max volumetric speed". If you reduce that, it will automatically "cap" your max speed. Each filament will have it's own setting for "Max volumetric speed" so if some can print faster you won't have to go muck around with all your print profile settings each time you switch filaments.
To compute the number based on the max speed you want to run, use this calculator: https://advanced3dprinting.com/pages/flow-rate-calculator. You can also run a volumetric flow calibration test (under the "calibration" menu) to figure out the highest flow your hotend can handle with a specific filament. Reduce that number by 20% for margin and you'll have a speed limit that will give strong prints without slowing things down more than necessary.
It's all in the data sheets. PA6-CF has significantly better impact strength - especially when it's had a chance to absorb some moisture. That goes hand in hand with PPA being significantly stiffer.
PPA-CF has a little better tensile strength and layer adhesion, but they're both good enough (assuming you can print hot enough) that the difference doesn't matter much. Last but not least, PPA-CF has a little higher heat deflection temperature.
My advice is set aside the steel rod and get the 40cr or 42cr hydraulic tubing listed in the ECM Tutorial document (16mm OD, 8.0 - 8.6mm ID). Then follow the tutorial. Yes, it's more expensive than stainless steel rod. That's because it's actually designed to contain the kind of pressure a 9mm cartridge will produce. The 40cr and 42cr steel is significantly stronger and harder than your stainless steel rod (which is probably 304 or 316 alloy).
I can't emphasize this enough -- taking shortcuts when making a 9mm barrel puts you at high risk of serious injury or even death. If you can't do it right due to cost or material availability, don't do it.
The NAG is a pretty advanced build. I've seen very few people get a successful build and most of them have a lot of experience.
Lot's of people recommend Glock clones, but to me they're really not the ideal starter project ...
- Relatively expensive. A quality slide and barrel and OEM parts kits cost as much or more than just buying a good used Glock.
- Obviously not an option in places that restrict the sale of gun parts.
- Too easy to slap all the parts together with zero understanding of how the thing actually works.
- You don't learn much. You're printing one part and buying everything else.
My advice is start with the Decker 380 (https://guncadindex.com/detail/RELEASE-Decker-3.0.1:d). So cool to be able to post links! Low cost, easy to print (you can actually print every part without any supports), easy to understand, and quite innovative. You can buy a barrel (no need to ECM) but that's the only gun part you need -- everything else is hardware store material. The design is quite safe, and doesn't demand a lot of manufacturing skill or experience or any special tools.
It's also fun to shoot (the release even includes an optional designed-in Recoil Assisted Reset trigger) and a real attention grabber. I had a new development version at the range Friday for testing and the ROs were literally lining up to take pictures of it :)
Gen 3 frames (virtually everything that takes FMDA rails) are fully backwards compatible with Gen 1 and Gen 2 parts.