(Updated 19-4-2024, added a modified stock)

This is a remix specially made to replace the extendable stock of the PP750 pcp airgun with a buffer tube folding stock. I designed the grip and merged it with Mussy's very well thought out folding design. The tube is mil-spec standard so you can use any commercial or mil-spec stock size you like. I also made it a little less angular and reinforced the walls of the knob. Mussy's folding stock designs are great for 3D printing, because they are strong and they have a good working durable mechanism.
Instead of using a hinge I simply sawed an M4 threaded rod to the proper size. The spring for the knob has a max diameter of 10.2 mm. The spring should not be too long/strong otherwise the knob can break due to the force of the recoil when closing the locking mechanism.

Stock:
Designed by “Mussy” and called “Spank Stock AR-15”. It’s downloadable on Cults3d https://cults3d.com/:404577, but due to the regulations in his country (UK), this design lacks an option to be able to tighten the stock. I asked mussy permission to add this by making a simple hole where you can slide in an M6 Nut through a hole at the top and tighten it using an m6 screw/bolt. Unfortunately, he could not add it on Thingiverse because of a strange server error, so i added the google drive link below for download.

Modified Stock:
https://drive.google.com/file/d/1KLH8WMCpSS8V2URaUesNs2tyJOQFFjIJ/view?usp=drive_link

Tools/hardware you need:

• M4 Rod/Bolt/Hinge (55mm)
• M3 Screw (25mm)
• Spring (diameter 10mm, length between 20 and 30mm)
• 2x M4 Nut
• 2x m4 Rings
• M6 Nut (modified stock)
• M6 Bolt/Screw (modified stock)

Print instructions:

No need to reorient the models on the build plate.

Material = PETG (I did 248 Celsius using a hardened steel nozzle)
Layers height = 0,16
Infill = 70%
Walls/Top/Bottom = Walls 3mm (0,4 line width), Top/Bottom 3.04mm (0,16 layer height)
Infill pattern = tri-hexagonal
Combing = off
Print speed = outer walls 30 mm/s, inner walls 40mm/s, infill 50mm/s
Print acceleration (buffer tube) = 350mm/s (to prevent falling over)

Supports:
Density = 20%

Grip =
Brim, touching build plate, lines or zig zag (connected).
Only the inside need support.

Tube =
Put support blockers on the upper part of the tube, brim, touching build plate, tree Support.

The tube itself does not need to have any supports actually, but you still need to add some to prevent it from falling over during printing. Best is to adjust the tree supports so the branches can reach the stock adjustment holes on the tube to make it more stable.

Knob =
Brim, Everywhere, Normal

Stock=
Brim, supports touching build plate only, Lines connected

Special thanks to “Mussy” for allowing me to create a remix of this design and sharing so many more nice designs for free. YOU RULE.