3/4" Copper Full/Semi-auto
Posted: Mon Dec 22, 2008 10:56 am
This is my second attempt at an automatic design, the first was cylinder-actuated (its posted here somewhere) and was basically a failure due to a glacial ROF. This design uses a blow-forward bolt instead. Lets start things off with a firing video, five shots at about 70 psi into an old trashcan filled with old sheet to absorb impacts. Once the covering paper is destroyed its kinda hard to see the follow-up shots. This video is with the semi-auto/blowgun attachment in place:
[youtube][/youtube]
The gun has 60" of 3/4" type L chamber and 51" of 3/4" type M barrel. The firing valve is a McMaster 3/" QEV. The gun can be filled through either a Quick-Disconnect setup or a shrader valve for use with CO2 canisters or bike pumps (the former for rapid fire, the latter so I can test it without using up gas). The QEV can be piloted either by a blowgun or a 70 psi pop-off valve, allowing semi or full auto firing characteristics. The rate of fire at full auto is about 1.5 rps, slower with semi because the blowgun drops the pressure lower after firing, requiring longer refill time. The magazine is made of wood and can hold about 15 rounds. The ammo in the video is simply dowel sections wrapped in duct tape, but also usable in this gun are steel-tipped darts (not suitable for firing in my basement into a target 3 feet away!). Why not go outside, you ask?
Some pics:
(almost) the entire gun
Looking down the barrel. The magazine is offset to one side to allow a clear(ish) line of sight and for better support.
The blow forward bolt housing and feed tray (shown without magazine obviously)
Bolt open
Bolt closed
From top: a ruler for scale, a 3/4" steel-tip dart, a shell from the original shell-ejecting design (couldn't make it happen, unfortunately), the blow-forward bolt housing, and the bolt itself.
And finally a video of a couple dry fires to show the bolt operating (yes it can shoot faster):
[youtube][/youtube]
[youtube][/youtube]
The gun has 60" of 3/4" type L chamber and 51" of 3/4" type M barrel. The firing valve is a McMaster 3/" QEV. The gun can be filled through either a Quick-Disconnect setup or a shrader valve for use with CO2 canisters or bike pumps (the former for rapid fire, the latter so I can test it without using up gas). The QEV can be piloted either by a blowgun or a 70 psi pop-off valve, allowing semi or full auto firing characteristics. The rate of fire at full auto is about 1.5 rps, slower with semi because the blowgun drops the pressure lower after firing, requiring longer refill time. The magazine is made of wood and can hold about 15 rounds. The ammo in the video is simply dowel sections wrapped in duct tape, but also usable in this gun are steel-tipped darts (not suitable for firing in my basement into a target 3 feet away!). Why not go outside, you ask?
Some pics:
(almost) the entire gun
Looking down the barrel. The magazine is offset to one side to allow a clear(ish) line of sight and for better support.
The blow forward bolt housing and feed tray (shown without magazine obviously)
Bolt open
Bolt closed
From top: a ruler for scale, a 3/4" steel-tip dart, a shell from the original shell-ejecting design (couldn't make it happen, unfortunately), the blow-forward bolt housing, and the bolt itself.
And finally a video of a couple dry fires to show the bolt operating (yes it can shoot faster):
[youtube][/youtube]