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Viu 18:05:42 Thu Jun 3 2010 |
Does anyone have any design suggestions? I'm thinking of modeling it after a Schmeisser MP-18/MP-28 but of course changing the magazine position and so on. I'm thinking of designing a similar mechanism to the Drozd but we'll see as I get further along in the design. The biggest question I have is, what is the best magazine design for pellets? I'd like to create a magazine that is high capacity yet isn't large. Any input would be appreciated, I may consider selling these if I get enough interest. Edit: I forgot to mention, I want to avoid a motorized feeder magazine like the Drozd blackbird has. anything from a hopper to a spring fed magazine would be ideal; if you have any ideas such as that, let me know. |
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Tbkahuna 21:39:16 Thu Jun 3 2010 |
You may end up needing to do some experimentation! .177 pellet skirts are very soft and deform easily. You might want to try a "belt" type feed like the Beretta CX4 Storm. You need something that will keep the pellet from crushing under the force of a feed system. A drum would work too. You can also see if a feed/magazine system like the Crosman 400 or 600 would work for your needs. I eventually want to do one in that style myself. You will have to pick the pellets that will work with a system like that, but they do work. On my Caselman, I redesigned it to shoot round balls because they are so much easier to handle, feed, and load. Orientation doesn't matter. It is .32 caliber, though. TBK |
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Viu 05:16:45 Fri Jun 4 2010 |
Thanks for the reply. I'm no stranger to experimentation. Do you mean the real Beretta CX4 Storm or a BB equivalent? I don't necessarily need to have mags, I just want a high cap storage for them that doesn't rattle around or look stupid. If this proves to be too much hassle, then I may consider just switching to regular BBs after seeing what the Drozd can do with them at 1,200 FPS. I guess what I'm trying to do is build a Drozd close since I'm so pleased with how it works, I just hate the MP7-ish machine pistol form factor and the feed system. Also this has crossed my mind but I'm not sure if it matters, but has anyone rifled their barrels when using BBs or pellets? I know in a real rifle or handgun the bullet engages the lands and follows the groves, spinning as it leaves the barrel. But since a pellet isn't going nearly as fast, nor is it heating up, I would think it wouldn't have the same effect. Am I wrong on this? I don't know how to rifle a barrel, but I'm sure the machinist could do it if I asked, the difference is really money and if rifling doesn't make a difference then I'll skip it. |
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Tbkahuna 11:43:11 Fri Jun 4 2010 |
I meant the pellet version of the CX4. It uses a belt to move pellets around a magazine body. I like the Drozd form factor, but I also like a LOT of others. I am building a new valve for the Drozd, but I originally designed it for a Thompson with the idea that it can be used for an MP5, AR, AK, HK or almost any other gun. I am going to work on the valve for the Thompson at the same time as the new Drozd valve. Yes, the barrels are typically rifled. The rifling normally isn't as deep and the twist rate varies. You can buy airgun barrels already rifled. I use or don't use rifled barrels depending on the application and expected range. I don't think anyone is getting 1200 fps out of the Drozd, though...yet... 1200 rpm, yes. Around 1000 fps, yes. Still really good. If you get something started you will get additional feedback. TBK |
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Viu 17:49:05 Fri Jun 4 2010 |
Ah, ok. Well I am looking for an accurate rifle, not the most accurate like something of sniper rifle quality, but decent so I think I will rifle the barrel. Is the greenhill equation still valid when it comes to rifling barrels for pellets? Because if so, I already have the barrel twist ratio figured out. hmm well I'd like to get as much as possible, and since I'm not strictly building a Drozd copy, there is room for modification. |
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Viu 00:54:48 Sun Jun 6 2010 |
The forend is 4 inches long and the barrel is attached via threads. The acronym stands for Small Caliber Fully Automatic Rifle, or SCFAR for short.    So how does this look so far? Last image I forgot to mention, this is not the whole end of the forend, just the top portion. |
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Tbkahuna 05:07:40 Sun Jun 6 2010 |
TBK |
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Viu 05:30:08 Sun Jun 6 2010 |
Soon I will start constructing the "receiver" housing and begin designing the internals. |
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Viu 22:18:32 Sun Jun 6 2010 |
As I said in my last post I redesigned the forend which has now become a forend/upper receiver. I'll post pics when the design is finished. Then I can move onto creating the internals. |
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Viu 17:54:36 Wed Jun 9 2010 |
Anyone have any ideas? I can't think of any way besides making the magazine longer, to have a high capacity magazine using a belt feed system. |
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Tbkahuna 02:17:47 Thu Jun 10 2010 |
What is your target round count? You could run a belt out of a small ammo can on the side of the gun. The mechanism would have to feed the belt in and let it fall out (or into another can). Keep after it! TBK |
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Viu 02:44:38 Thu Jun 10 2010 |
However if I decide to go that route, I really hope I don't have to buy a CX4 just to look at the mag well, and reverse engineer the mag well to utilize the magazines. |
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delysid 21:36:15 Thu Jun 10 2010 |
someone else on this forum has worked on this project, dont know how far he got with it as i lost track of postings. i have worked on this feed system for a long time and gave up for less frustrating projects. the prototypes i made were a little bulky in size but held several thousand rounds. consumed a lot of air even regulated down. |
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Viu 14:42:06 Fri Jun 11 2010 |
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Tbkahuna 17:58:26 Fri Jun 11 2010 |
By "pellet" do you want to use a traditional skirted design, a sturdier skirt design like the old Sheridan .20 caliber, or do lead balls count, too? From the bottom of the list up, it will be easier to make a reliable feed. TBK |
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Viu 19:40:23 Fri Jun 11 2010 |
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Tbkahuna 20:17:02 Fri Jun 11 2010 |
TBK |
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Viu 22:52:01 Fri Jun 11 2010 |
However I do have one question, what am I looking for in a co2 valve? I assume it's a valve anyways, the thing that the 88 gram co2 cartridge screws into. And is this the same valve paint ball tanks use? |
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Tbkahuna 01:18:56 Sat Jun 12 2010 |
By CO2 valve are you talking about a pin valve that just opens the tank for use, or a regulator? Paintball tanks have a pin valve for opening the tank when it is screwed in to the gun and the pin is pressed, as well as some have regulators to lower the pressure. Your use would depend on what pressure you wanted to design the gun for and the protection you put in place to prevent a catastrophic failure (like a rupture disk). TBK |
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Viu 01:51:06 Sat Jun 12 2010 |
Other than that I have no idea where to begin regarding co2 plumbing and such. EDIT: Here is where I'm at so far with my design. The biggest problem with my design currently is making something that goes from the back of the lower receiver to the back of the forend that doesn't look ridiculous, yet saves metal when CNCing and looks nice. Since my last picture post I have worked more on the ar15 lower receiver and have been modifying it so it is in accordance with any ATF regulations and fits my needs. As it is now, it would take someone far longer to modify this into a real ar15 receiver than it would if they had just started with a slab of aluminum and CNC'd it themselves. I've had to completely redesign the forend, but with good reason. Since I plan on using this with an ar15 front and rear sight I found the distance between the center of the bore and the top of the picatinny rail so the sights will hopefully be accurately lined up within .000" Unfortunately I found that the 88 gram co2 tank would not fit inside the buffer tube due to the buffer tube being about .2" too small. So rather than compromise usage of ar15 stocks I put the co2 tank in the forend. to keep it accessible I made co2 tank chamber about an inch+ shorter than it needs to be and made a custom cap. I finally figured out how to rifle the barrel, so that is now complete. And due to the longer forend to accommodate the co2 canister the barrel is now threaded 8 inches inside it, leaving only 8 inches exposed which I quite like. I've added four picatinny rails for a nearly unlimited combination of accessories for whatever the job calls for.    Last image |
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Viu 05:46:51 Sat Jun 12 2010 |
 
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Viu 03:35:30 Tue Jun 15 2010 |
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Tbkahuna 13:48:30 Tue Jun 15 2010 |
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Viu 15:16:03 Tue Jun 15 2010 |
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Tbkahuna 17:34:14 Tue Jun 15 2010 |
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Viu 04:55:25 Fri Jun 18 2010 |
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Viu 03:36:48 Sat Jun 19 2010 |
1. How can I conserve CO2? (controlling the amount that is released for say, target practice and one that allows a full shot of co2 for something you want to exterminate) 2. How can I control the rate of fire? I saw the Caselman video and I'm convinced that is definitely the way to go, however I also looked at the plans and there doesn't appear to be a rate of fire selector. 3. How can I stop the rifle from firing once the 30 rounds have been exhausted to save what would otherwise be wasted co2 bursts? Things like advancing the magazine I think will be easy enough to do. I would want to base it off something like the caselman, but I don't have that much room to work with. I've got roughly 6.791+ inches to house any mechanical components. Since I'm still going to be using a .177 caliber BB, there will be less mass to push but at the same time, I should get somewhere in the 1000+ fps range correct? |
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Tbkahuna 23:32:03 Sat Jun 19 2010 |
The only fire selector on the Caselman is semi- or full- auto. You pull the trigger a little bit for semi, and further for full auto. There isn't a rate, as in 600 rpm then select 1000 rpm. I got various rates of fire by changing the moving mass and the springs. You can stop the firing when it is out of ammo by making a magazine follower (or a space in the mag if you go with the "belt" type mags) that gets in the way (or out) when out of ammo. You may also design it so that it won't recock if it doesn't have a projectile in the barrel to keep the pressure up enough to recock it. That would work much better with ammo that seals the barrel, like lead, so the difference between ammo in, and ammo out, is more dramatic. Lighter ammo will go faster to a point. Smaller diameter means less efficient transfer of energy. (think big pipeline vs garden hose) If you are asking about the velocity of a .177 steel BB from a Caselman, I can tell you that a much heavier .25 caliber steel ball will go about 1000 fps. TBK |
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Tbkahuna 23:33:48 Sat Jun 19 2010 |
http://bb.bbboy.net/straferbbmachinegunownersgroup-viewthread?forum=5&thread=64 |
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Viu 01:35:15 Sun Jun 20 2010 |
I've been thinking of going with a larger caliber pellet for a while now, however once I do that I can no longer use the premade Umarex CX4 magazines. I'm not sure I want to go with the belt fed system anymore anyways, however I saw the caselman magazine and thought it looked kind of ridiculous. .22 seems like the best option for me but if I'm not mistaken the issue of deforming pellets in a spring fed mag is still a reality. |
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Tbkahuna 03:29:50 Sun Jun 20 2010 |
I got 1175 fps with a .177 bb out of an 18" barrel. That is smoking fast!! You can have a velocity quite a bit less and still have a great gun. TBK |
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Viu 04:30:35 Sun Jun 20 2010 |
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Tbkahuna 04:58:13 Sun Jun 20 2010 |
I wound my own springs. You can make the spring as strong or as weak as you need. TBK |
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Viu 05:07:46 Sun Jun 20 2010 |
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Tbkahuna 05:25:59 Sun Jun 20 2010 |
The spring has to overcome all the weight and friction. |
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Viu 22:44:11 Sun Jun 20 2010 |
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Tbkahuna 01:23:43 Mon Jun 21 2010 |
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Viu 22:10:34 Thu Jun 24 2010 |
First let me start off by saying now I have completely shifted gears into a whole different kind of pellet rifle. Instead of building an m16 style lower receiver rifle that uses a caselman type system, I've decided to basically create an m16 that fires .22 pellets using co2, but uses the same bolt, same trigger assembly, auto sear, barrel style and pretty much everything else you can think of. The possible solution to this problem would be a .22 conversion ar15 magazine. I think I'd have to mount each pellet in a .22 shell minus any powder or primer. Thus ending any problem with squishing pellets. |
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Tbkahuna 05:50:23 Fri Jun 25 2010 |
Two things come to mind: 1. Be careful in making anything that could be considered a firearm. You don't want something that could easily fire real ammo. 2. Instead of the cartridge, you might want to look at what RAP4 does. They use a cylinder drilled out for the ammo. Do a search on google and you will see the concept. |
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7echo 23:52:06 Wed Jul 14 2010 |
PM-16 video [487 clicks] |
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Tbkahuna 07:29:13 Sun Jul 25 2010 |
It uses a cylinder and ratchet to feed ammo as I remember. It has recoil effect, too. TBK |
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jaythedogg 20:43:33 Sun Aug 15 2010 |
The PM16 is dead. I was doing PR work for NewMatics & they shut down, George Parks was acting CEO & Jim Bendel was their production manager. Chuck Lee did sales as well as minor PR for military & police. They owe me a PM16 & cash, but I will never see it. Doc has disappeared once again & just as an FYI, there was only one working PM16 ever produced, it's in the videos. You can find Mark Schavone's patents using Google's patent search & see how the PM16 worked.... Well, was supposed to have worked. Very big let down for all. |
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Tbkahuna 00:58:13 Mon Aug 16 2010 |
Did it not work as well as advertised? |
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tgwms 04:04:56 Sun Aug 29 2010 |
it's working and will be refined for short run production. |
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jct842 00:06:42 Sun Oct 3 2010 |
viu seens to be fixed on using an 88gm tank. If it was me I would scrap that idea totally. the cost to experiment with an 88 is way too much, once it is in and you have fired one shot you can't take it out with out loosing all the gas. O-Rings and a tube of what ever size you like makes a nice reservoir, and you fill from either a paint ball or a large 20lb tank. a paint ball tank can be used if you want removable, also can make home made removable tanks using tube and O-Rings. If you just have to use pellets and not balls consider large drums which can solve the deforming in stacked magazines. the trash can .20 is a good choice but for the price. a full auto is going to consume them quickly. If it was me I would look to finding a size of buckshot that you are happy with the consistency and fit to a barrel. again the cost of shooting will be much better than pellets. the casslman .31 ball seems ideal. one other fly in the ointment with CO2 and don't get me wrong I love working with CO2, is the fact that it gets cold with rapid use and thus lowering the pressure. I will be following this as I want to have a larger cal air machine gun too. John |