Looking to create a full auto pellet gun
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Viu
18:05:42 Thu
Jun 3 2010
Looking to create a full auto pellet gun
I have access to various CNC machines (mills, lathes, you name it) and I am adept at CAD software. I'm looking to create a fully automatic rifle or SMG that shoots .177 pellets and maybe also .117 BBs.

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.

Tbkahuna
21:39:16 Thu
Jun 3 2010
Re: Looking to create a full auto pellet gun
Viu,

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

Viu
05:16:45 Fri
Jun 4 2010
Re: Looking to create a full auto pellet gun
Tbkahuna,

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.


Tbkahuna
11:43:11 Fri
Jun 4 2010
Re: Looking to create a full auto pellet gun
Viu,

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

Viu
17:49:05 Fri
Jun 4 2010
Re: Looking to create a full auto pellet gun
Hmm, the CX4 belt magazine system looks excellent. I assume it fires a shot, and then some type of screw mechanism advances the belt one position?

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.



Viu
00:54:48 Sun
Jun 6 2010
Re: Looking to create a full auto pellet gun
This isn't much but it's a start I guess. What your looking at is the barrel and what I suppose is some type of forend with a picatinny rail.

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.

Tbkahuna
05:07:40 Sun
Jun 6 2010
Re: Looking to create a full auto pellet gun
That's a good start. Do you plan on using CNC to build your design? That would be great.

TBK

Viu
05:30:08 Sun
Jun 6 2010
Re: Looking to create a full auto pellet gun
Yes, CNC seems like the way to go. However since I posted the pics I've radically changed my design. I noticed the picatinny rail wasn't perfectly centered which would cause problems with accuracy regarding a scope or the sight alignment. The new forend is much smaller, however this is good since I don't plan on holding it like a standard rifle. It will have a bottom mounted picatinny rail as well that will have some sort of vertical or maybe horizontal handle. I also lowered and leveled the top rail to the top of the barrel.

Soon I will start constructing the "receiver" housing and begin designing the internals.





Viu
22:18:32 Sun
Jun 6 2010
Re: Looking to create a full auto pellet gun
well, instead of doing something original, I went out and found an ar15 lower receiver model that I will modify and adapt for my uses. Basically this gives me a premade magwell, pistol grip and buttstock attachment area that will use readily available components. I'm going to have to modify the mag well a bit but so far, this is turning out well.

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.



Viu
17:54:36 Wed
Jun 9 2010
Re: Looking to create a full auto pellet gun
I've kind of reached a block here. I'm not sure if I should design my own belt fed magazine, or if I should just adapt my rifle to use the Beretta CX-4 ones.

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.

Tbkahuna
02:17:47 Thu
Jun 10 2010
Re: Looking to create a full auto pellet gun
Maybe you will come up with some new ideas. They will depend on what you actually want to accomplish. If you only want 50 round capacity you can think differently than if you want 1000 round capacity.

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


Viu
02:44:38 Thu
Jun 10 2010
Re: Looking to create a full auto pellet gun
Well I really want to avoid the machine gun style belt feed system where the belt is ejected once all the rounds are empty. I was thinking maybe some sort of pulley system but I have no idea what I'm doing in that respect and I may just design it to work with CX4 mags which are for the most part, readily available and have a somewhat realistic capacity.

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.

delysid
21:36:15 Thu
Jun 10 2010
Re: Looking to create a full auto pellet gun
vortex feed magazine is a very good option, same as straffer clones, a large reservoir of bb's is pressurized by regulated compressed air or co2 and the bb's just funnel out of a hole in this pressure chamber, feeds 100-plus rounds per second in strafers, thats more than enough to create reliable ammo feed.
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.

Viu
14:42:06 Fri
Jun 11 2010
Re: Looking to create a full auto pellet gun
Yes, however the problem is I'm not using BBs, I'm using Pellets. Therefore a hopper is largely out of the question. I really wish it wasn't so but it is. I think my only choice is a belt fed magazine.

Tbkahuna
17:58:26 Fri
Jun 11 2010
Re: Looking to create a full auto pellet gun
Viu,

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

Viu
19:40:23 Fri
Jun 11 2010
Re: Looking to create a full auto pellet gun
I assume a .177 caliber pellet is skirted, and yes lead balls are out of the question.

Tbkahuna
20:17:02 Fri
Jun 11 2010
Re: Looking to create a full auto pellet gun
Ok. You have your work cut out for you! Post some pictures as you progress. I'll let you know if I think of anything helpful.

TBK

Viu
22:52:01 Fri
Jun 11 2010
Re: Looking to create a full auto pellet gun
Well that may take a while, as I haven't even begun to design the internals. I'm going to research pressures and such to make sure I don't do something stupid and blow out an eye.

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?

Tbkahuna
01:18:56 Sat
Jun 12 2010
Re: Looking to create a full auto pellet gun
Yes, safety first!

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

Viu
01:51:06 Sat
Jun 12 2010
Re: Looking to create a full auto pellet gun
I believe the pin valve, I can tell you what I plan on achieving with this build. I'm looking for selectable fire settings and fps. For example, which ever FPS works best and saves co2 whilst shooting at paper targets or plinking, etc. And a high fps setting for shooting at game or, well something I want dead and really have no regard for the amount of co2 I'm using. The selective fire mode would be for single shot, 3 round burst and full auto. I'm planning on using a system similar to the drozd, except minus the PIC, just using a solenoid to facilitate the bursts.

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


Viu
05:46:51 Sat
Jun 12 2010
Re: Looking to create a full auto pellet gun
Don't you just love teaser pics :smile:




Viu
03:35:30 Tue
Jun 15 2010
Re: Looking to create a full auto pellet gun
Rifle Body Finished.



Tbkahuna
13:48:30 Tue
Jun 15 2010
Re: Looking to create a full auto pellet gun
What happened to the pictures?

Viu
15:16:03 Tue
Jun 15 2010
Re: Looking to create a full auto pellet gun
Don't know, they all display fine for me, which ones are you talking about?

Tbkahuna
17:34:14 Tue
Jun 15 2010
Re: Looking to create a full auto pellet gun
I am working out of a different location today. It must be a new security feature here at the office.

Viu
04:55:25 Fri
Jun 18 2010
Re: Looking to create a full auto pellet gun
Scratch what I said earlier, I'm about 87% finished. I'm 100% finished with the basic design but I still need to add holes and features for the parts.






Viu
03:36:48 Sat
Jun 19 2010
Re: Looking to create a full auto pellet gun
Well now that I've thought about it, I'm thinking maybe a mechanical system might be the way to go. But I have a few questions regarding this.

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?



Tbkahuna
23:32:03 Sat
Jun 19 2010
Re: Looking to create a full auto pellet gun
Viu,

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

Tbkahuna
23:33:48 Sat
Jun 19 2010
Re: Looking to create a full auto pellet gun
Here is my post about .25 caliber steel from the Caselman:

http://bb.bbboy.net/straferbbmachinegunownersgroup-viewthread?forum=5&thread=64



Viu
01:35:15 Sun
Jun 20 2010
Re: Looking to create a full auto pellet gun
Hmm well thanks for the info. I had read that larger caliber bullets when speaking about air rifles, are slower and therefore less lethal. But I've seen the caselman video on youtube and I'm pretty sure now that they are just as lethal as a smaller caliber.

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.

Tbkahuna
03:29:50 Sun
Jun 20 2010
Re: Looking to create a full auto pellet gun
Viu,

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

Viu
04:30:35 Sun
Jun 20 2010
Re: Looking to create a full auto pellet gun
Well then I suppose it's not all bad. Let me start over by asking how does the caselman magazine work? I've looked at it and the only thing I can say about it is it's spring powered but I'm guessing it's a spring that isn't that powerful?

Tbkahuna
04:58:13 Sun
Jun 20 2010
Re: Looking to create a full auto pellet gun
Yes, it is spring driven. Are you talking about the original Caselman mags, or my redesigned version? I tried to simplify it for shooting round ammo.

I wound my own springs. You can make the spring as strong or as weak as you need.

TBK

Viu
05:07:46 Sun
Jun 20 2010
Re: Looking to create a full auto pellet gun
I'm speaking of the original caselman mags, if I use a weaker spring that should reduce the amount of pressure on the pellets and effectively stop them from deforming, correct?

Tbkahuna
05:25:59 Sun
Jun 20 2010
Re: Looking to create a full auto pellet gun
Doubtful. It doesn't take much force to deform a skirted lead pellet.

The spring has to overcome all the weight and friction.

Viu
22:44:11 Sun
Jun 20 2010
Re: Looking to create a full auto pellet gun
Hmm well then I'm all out of ideas. Your modified magazine takes BBs so that doesn't really apply to my design..I'm at a dead end...

Tbkahuna
01:23:43 Mon
Jun 21 2010
Re: Looking to create a full auto pellet gun
Keep at it. You may come up with a great idea that will work! I stuck to round ball ammo because I wanted to spend more time building and shooting than testing magazines.

Viu
22:10:34 Thu
Jun 24 2010
Re: Looking to create a full auto pellet gun
Hmm well I may have found a magazine solution.

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.

Tbkahuna
05:50:23 Fri
Jun 25 2010
Re: Looking to create a full auto pellet gun
Viu,

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.




7echo
23:52:06 Wed
Jul 14 2010
Re: Looking to create a full auto pellet gun
Your project reminds me of the Newmatics PM-16 air rifle


PM-16 video [528 clicks]



Tbkahuna
07:29:13 Sun
Jul 25 2010
Re: Looking to create a full auto pellet gun
I had high hopes for the PM-16. I had talked to Doc and he was going to build me a gun. However, I completely lost touch with him. I think he may have gotten really busy with a big contract and put this aside. I am still hopeful that he will make some of them available.

It uses a cylinder and ratchet to feed ammo as I remember. It has recoil effect, too.

TBK

jaythedogg
20:43:33 Sun
Aug 15 2010
Re: Looking to create a full auto pellet gun
Quote: Tbkahuna at 07:29:13 Sun Jul 25 2010

I had high hopes for the PM-16. I had talked to Doc and he was going to build me a gun. However, I completely lost touch with him. I think he may have gotten really busy with a big contract and put this aside. I am still hopeful that he will make some of them available.

It uses a cylinder and ratchet to feed ammo as I remember. It has recoil effect, too.

TBK


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.

Tbkahuna
00:58:13 Mon
Aug 16 2010
Re: Looking to create a full auto pellet gun
Well that's not good. Maybe someone will build another one someday.

Did it not work as well as advertised?

tgwms
04:04:56 Sun
Aug 29 2010
Re: Looking to create a full auto pellet gun
http://www.fullyautomaticairgun.com/newsletter100827.html

it's working and will be refined for short run production.

jct842
00:06:42 Sun
Oct 3 2010
Re: Looking to create a full auto pellet gun
re-reading this thread I have a couple observations:

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



Looking to create a full auto pellet gun
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