The SL-9 V2.8

about

The SL-9 by Hoffman Tactical

The SL-9 is a 3D printable AR-9 lower receiver. The lower uses a double-stack 9mm Glock mag and features a last-round bolt hold open (LRBHO).

Based on the V4.8 SL-15 lower, the entire back end of the SL-9 lower rear of the bolt catch is in fact the same as it’s AR-15 counterpart. The forward end of the lower has been heavily modified to accommodate the Glock magazine and the bolt-hold open mechanism. However, the swivel pin plates are the same as on the SL-15, allowing for the same printed cheek plates and, optionally, metal swivel pin plates.

AR-9’s use a fixed ejector, usually made from a steel plate bolted or pinned into the lower. This metal part is not standardized and would add cost and limit access if it were made custom. The The solution was to use a printed ejector. Much testing has shown these to hold up well when printed on the proper filament. Even when printed in PLA Pro, the ejectors hold up very well. The ejector is retained by the upper, eliminating the use of fasteners.

The mag catch is similar to the ejector in that there are no standardized AR-9 mag catches as There are AR-15 catches. The solution is the same: the mag catch is printed. A standard AR-15 mag catch spring is used with the printed ejector to simplify sourcing.

A LRBHO is a challenge to 3D print due to the need for high stiffness and small parts. The solution was to use a hexagonal metal shaft to transfer the torque from the magazine follower at the front to the bolt catch in the rear. A combination of a sliding element and swinging lever were used in the front to eliminate layer adhesion issues. The last feature was to place the rear lever below the main body of the catch, rather than under the standard lifting nub. This greatly reduces friction and has resulted in zero failures to hold open during testing. The metal shaft is easy to obtain from a cheap hex key or aluminum extrusions.

The rest of the lower part is very similar to the SL-15. A rib on the left side works in combination with the buffer band to produce a strong buffer tower. The pistol grip is integrated to improve the strength and ergonomics of the lower.

files

File Extension
SL-9 V2.8.zip zip

versions

Version: 1.0.0 latest

initial upload

about

The SL-9 by Hoffman Tactical

The SL-9 is a 3D printable AR-9 lower receiver. The lower uses a double-stack 9mm Glock mag and features a last-round bolt hold open (LRBHO).

Based on the V4.8 SL-15 lower, the entire back end of the SL-9 lower rear of the bolt catch is in fact the same as it’s AR-15 counterpart. The forward end of the lower has been heavily modified to accommodate the Glock magazine and the bolt-hold open mechanism. However, the swivel pin plates are the same as on the SL-15, allowing for the same printed cheek plates and, optionally, metal swivel pin plates.

AR-9’s use a fixed ejector, usually made from a steel plate bolted or pinned into the lower. This metal part is not standardized and would add cost and limit access if it were made custom. The The solution was to use a printed ejector. Much testing has shown these to hold up well when printed on the proper filament. Even when printed in PLA Pro, the ejectors hold up very well. The ejector is retained by the upper, eliminating the use of fasteners.

The mag catch is similar to the ejector in that there are no standardized AR-9 mag catches as There are AR-15 catches. The solution is the same: the mag catch is printed. A standard AR-15 mag catch spring is used with the printed ejector to simplify sourcing.

A LRBHO is a challenge to 3D print due to the need for high stiffness and small parts. The solution was to use a hexagonal metal shaft to transfer the torque from the magazine follower at the front to the bolt catch in the rear. A combination of a sliding element and swinging lever were used in the front to eliminate layer adhesion issues. The last feature was to place the rear lever below the main body of the catch, rather than under the standard lifting nub. This greatly reduces friction and has resulted in zero failures to hold open during testing. The metal shaft is easy to obtain from a cheap hex key or aluminum extrusions.

The rest of the lower part is very similar to the SL-15. A rib on the left side works in combination with the buffer band to produce a strong buffer tower. The pistol grip is integrated to improve the strength and ergonomics of the lower.

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Metrics

Views

422

Downloads

42

Project Info

release date

May 26, 2024

artifact type

Printable project

library category

Printable Firearms

fabrication method

Printable Lower / Frame

release country

United States

language

English

license

No license

Firearm Info

type

Pistol-Caliber Carbine

platform

AR-9

caliber

9x19mm

part

Lower Receiver

files

File Extension
SL-9 V2.8.zip zip

versions

Version: 1.0.0 latest

initial upload

The files shown on this site are only available to U.S. Persons, as defined at 22 C.F.R. 120.15. The files are also not available to persons outside the United States or to residents of and persons in the State of New Jersey, with the exception of Federal Firearms Licensees.

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