Like my first homemade rifle, this one is composed of almost all PVC. The receivers are again1/1/4 PVC. The barrel is 1/2 PVC and the bolt is 1, 200psi PVC. 1/2 couplers were used as spacers. Balsa was used to a small extent to create the flat surface necessary. Mainly for the magazine and the mag well. For higher stress flat pieces like the trigger crank, PVC endcaps were used.
Some various configurations:
loser (faux suppressor)
Barrel Length: 12
Plunger Travel: 6
Overall Length: 34
Caliber: Nerf Micros
Operation: Fast-Action Magazine Fed
Magazine Capacity: 5
ROF: ~50 RPM Accuratly
Range: 70-80 ft
The upper receiver cotains the barrel, bolt, and plunger assemblies. It is constructed of 1/1/4 PVC. The magwell was built by fabricating custom pieces out of 1/1/4 T joints. The mag well was fabricated as a separate unit and then bonded to the upper receiver. The feed and ejection ports were then cut and the feed ramp was formed by grinding a ramp into the forward portion of the magwell and upper receiver. The feed ramp is what guides the shell as it is pushed out of the magazine up into the chamber. Slots for the charging handle and action spring rod were cut lastly.
Barrel and Chamber:
The barrel is the simplest part of the rifle, it is just 1/2 PVC. The camber is the rear portion of the barrel that the shell sets in. The chamber needed to be a tight fit around the shell. 1 PVC is close around 1/2" couplers but there is still a substantial gap. In order to create a tighter fit I cut a 1/4" sliver out of a section of 1 PVC and closed the gap to create a piece of PVC with a <1 inner diameter. The shell is now a near perfect fit in this portion of PVC.
The bolt is quite simply a straight piece of 1 200psi PVC. The bolt face is a coupler with a section of ½ PVC set in it and is placed in the 1 PVC about1/2 from the end. The bolt face has 2 concentric O-rings on it to create a positive seal against the rear of the shell. A short piece of carbon rod stick out of the right side of the bolt to act as a charging handle. It passes just below the air passage in the bolt face. The action spring rod passes vertically through the center of the bolt. This spring closes the bolt after the plunger is locked to the rear. It is a high displacement fairly linear stiffness spring that is strong to strip a round off the magazine but not a burden to pull back in addition to the main spring.
The extractor is what engages the rim of the shell and pulls it out of the chamber for ejection. It is made out of a section of 1 PVC and the hook portion is composed of layered ½ coupler sections. It fits in a cut-out portion of the bolt so that the edge of the extractor is about Ό above the bolt face (the size of the rim on the shells). The extractor is fastened with one wrapping of electrical tape around the bolt. This allows the extractor to flex out over the rim of the shell and also allows for easy changing if it were to break. Extractor breakage is a pretty common problem in real firearms. I anticipate it being a problem as well in this rifle.
Action Spring Image
I had a few ideas going for an ejector. Originally I had planned to use a passive ejector as in handguns. This meaning there is a piece that is fixed to the frame that would contact the rear of the shell opposite the extractor as the bolt moves rearward to kick the spent shell out. With the need for a plunger tube directly behind the bolt I could not use this type of ejector as it would require cutting a groove in the bolt. I opted for a dynamic (sprung) ejector as in use in most automatic rifles. The ejector is a short piece of 0.2 carbon rod placed opposite the extractor on the bolt face. A whole was drilled on the edge of the boltface about 1/1/2 deep and just wider than the carbon rod. A click pen spring was used for the ejector spring. A groove was cut in the side of the ejector rod and a retaining pin was inserted crossways to hold the ejector in. The ejector is flush with the front rim of the bolt and is depressed by the shell as it is chambered. The shells are heavy so they do not eject far from the rifle, but they do reliably clear it. I may try a strong er spring to see if I can get a more powerful ejection. But I don`t have any problems with it at this point so it if it ain`t broke don`t fix it
The top portion of the rifle serves to cover the action spring and also serve as a platform for both iron sights and optics. A picatinny rail was fabricated out of layered PVC and bonded to the receiver cover. This rail allows the attachment of any optic. The receiver cover is attached with 4 screws.
Receiver Cover Image
The plunger is a piece of 1/2 PVC 7 long. It rides inside the 1 PVC of the bolt and maintains a seal with 2 Orings. A 1/2 cap plugs off the end. A 1/2 coupler sheathed in 1 PVC is at the rear of the plunger. This is where the main spring attaches. A larger washer was cut and fit on the front of this portion of the plunger. This is where the trigger catches the plunger when drawn back. The washer is present to prevent gouging that would take place if it were only PVC.
The lower receiver is everything from the magwell and back below the upper receiver. It consists of the pistol grip, buttstock, and trigger mechanism. The pistol grip was fabricated from 1 PVC. The trigger sear was forced to be placed very far to the rear of the gun because of the retracting plunger tube (bolt). I had to come up with a mechanism to pull the plunger catch down as the trigger was pulled.
Lower Receiver Image
Lower Receiver Image
I had a few ideas going for a trigger. The one I ended up with uses a crank to convert the horizontal motion into vertical motion. The plunger catch is 1/16 music wire and works very well. The crank sits just ahead of the catch rod and is fastened to the lower receiver. A pushrod connects the trigger to the crank. All pivot joints were inserted with brass to reduce wear and friction that would occur with PVC joints. The trigger is very crisp and smooth. See the video. The rear of the plunger tube is beveled and depresses the catch rod as it is moved rearward.
Fire Control Group Image
Fire Control Group Image
-- Action Cycling
(same as posted before)
-- Trigger Mechansim
-- Loading a Magazine
--Closeup of the breach and action
--Closeup of the mag and action chambering a round slowly
--Closeup of the action making a full cycle slowly
-- Shooting a Full Magazine
-- Shooting Again
(This illustrates the ROF of the rifle. I pause between each shot to reacquire the target. Max ROF would be higher.)
Ranges seem to be around 70-80 feet. Comperable to a good croosbow I guess but with much better ROF and cool factor. Nothing phenomenal but not bad either. I have an Extra power spring on order which should boost range some. The seal the dart makes in the barrel effects the range. The dart seal needs to be very good but not too tight. A dart that does not make a good seal will not leave the barrel. The plunger and barrel are sized together so if air leaks past the dart the plunger will stop before the dart leaves the muzzle.
The rifle feels great when you hold it. It has a good weight and is well balanced. The pull on the stock is just right. I was worried it was going to be too long because it was kind of governed by the bolt, plunger, and main spring. The trigger is positioned just right and the magazine catch is just ahead of the trigger which can be operated by the trigger finger without removing your right hand. The sights mounted on the receiver cover are positioned at the right height to get a good cheek weld on the stock. I am ecstatic with how it turned out. It turned out MUCH better than I had even originally want it to.
I am still working on updating the plans to the current configurations. I will psot those as soon as I finish em up
I have about 300 pictures at most every phase of construction and more videos. If anyone wishes to see more on a specific portion I can post more. I am sure you all will have questions so ask away ..
Edited by boltsniper, 09 April 2005 - 11:51 PM.