Parametric Brass Catcher for AR-15 and AR-10 with Mason Jar Thread

PLA and PETG have a rough time with hot brass and port pressure, so I designed this catcher around carbon fiber nylon. It hangs from your top Picatinny rail, sits over the ejection port and funnels brass down into a screw-on bin. The bottom is a standard wide-mouth mason jar thread, so the bin is only the first option. Screw on the bag collar, a metal wide-mouth jar, or anything you design to the same thread. Quick start - Find your caliber below. It tells you the hood set and the bin.

- Print the Rail Fit Test and Thread Fit Test in PLA Pro. Try them on your rail and on a real jar.

- Print the hood, clamp and bin in PLA Pro and check the fit on your cleared rifle. Do not fire it.

- Happy with the fit? Print the real set in Fiberon PA612-CF15 and anneal it.

- Work through "Test it before you trust it" below.

Calibers - AR-15 hood, 60 round bins: 5.45x39, 5.56 / .223, .224 Valkyrie, .300 Blackout, 6mm ARC, 6.5 Grendel, 6.8 SPC, 7.62x39, .350 Legend

- AR-15 hood, 40 round bins: .450 Bushmaster, .458 SOCOM, .50 Beowulf

- AR-10 hood, 40 round bins: .308 / 7.62x51, 6.5 Creedmoor, 6mm Creedmoor, .243 Win, .260 Rem, 7mm-08, .338 Federal

- Long Action hood, 30 round bins: .30-06, .270 Win, 7mm Rem Mag, .300 Win Mag

The Long Action set is a starting point for long-action gas guns only, so measure your rifle first. It isn't for bolt guns, because the hood would block the bolt handle. Every bin is 93 mm across with the same thread, so any bin fits any hood. Will it fit your rifle? - You need a true Picatinny top rail from about 69 to 123 mm forward of the port center. A rail section bolted on top changes the height, so measure it.

- The rifle numbers in the file are estimates. I couldn't find a published drawing, so they came from forum figures and geometry. The hood has margin, but your real numbers are better.

- Enter your measurements in the Customizer under "Rifle fit" if something doesn't clear.

- The hood slides up to 5 mm fore or aft in its slots to center the port.

The thread - The hood socket is the lid side of a wide-mouth mason jar (86-450 finish), and attachments are the jar side.

- Numbers: 86 mm thread outside diameter, 82 mm neck, 6.35 mm pitch. Sources disagree and I haven't measured a jar, so try the Thread Fit Test on a real jar before you print a hood.

- Fine to screw on: the printed bin, the bag collar, a metal wide-mouth jar or cup, or anything printed in nylon to those numbers.

- Never glass. It would sit on a recoiling rifle with hot brass dropping into it. Thin plastic jars will soften or melt.

- There's no snap lock, because that would stop other attachments fitting. Turn the bin until the rim seats and check it after your first magazine.

Cooling and sifting - The bin floor is a hex mesh with 3.5 mm holes, so dust and loose powder fall out while brass stays in.

- Nine 5 mm open slits run from the floor to the shoulder so brass cools and nothing packs in at the edge.

- That dust isn't clean, because fired primers leave lead residue. Dump the bin outdoors or over a bin, and wash your hands after.

Materials - Real parts: Polymaker Fiberon PA612-CF15. Its heat deflection is 175 C at 0.45 MPa and 114 C at 1.8 MPa.

- Fit checks only: Polymaker PLA Pro. Do not fire PLA or PETG parts. PLA Pro's heat deflection is 58 C, and hot brass and a warm handguard go past that.

- My worst-case estimate for a full bin is 115 to 125 C. On long strings, dump a hot bin instead of topping it up.

- The hood doesn't seal, so it can't hold pressure. The mouth stands at least 16 mm off the receiver, and ten slots vent out and forward, not back at your face. Take extra care testing if you run a suppressor.

Printing the real parts - Nozzle: 250 to 300 C, hardened, 0.4 mm or larger

- Bed: 40 to 50 C, never above 50

- Chamber: room temperature, door open

- Part fan: off

- Layer height: 0.20 mm