USAS-12 Type Thingy

[MDK_Marshal]

Right. I've gone and done something stupid. I've got myself a plan for a gun that I'm just gona have to make.

 

Quite a while ago, I was thinking of making a shotgun from scratch - never panned out, though. But, I realised that if I used a standard loading system, all I had to do was make an extended hop rubber and Make the loading action cycle more than once while the spring was being compressed.

 

So.

 

If I was to, say, do some fun stuff with an M4... like, put two extra nubs on the sector gear to load 3 BB's at once, Make myself an extended hop chamber (cut a slit in top of the barrel and add an o-ring), and modify for semi auto only... We have ourselves a shotgun, ladies and gentlemen!

 

I reckon the most rounds you could load in one cycle would be 3 - the sector gear just isn't big enough to add many more nubs.

 

I'm also considering the possibility of getting a G3 lower and mating it to the aforementioned M4, so it takes G3 mags - reason being that they look like they could actually hold 12 gauge shells!

 

It's just a pipe dream at the moment, But I reckon it could work... Is there anybody with enough money to source the bits and enough craziness to try it before I can?

[ED-SKaR]

if you put more than one BB in the barrel at the same time, the BB at the front flys much futher than the BB at the back, giving an unrealistic shotgun spread.

 

 

 

Other than that, your "multi-nub" idea sounds very feasable, and would probably work wonders, now give it full auto and you do get a USAS-12 or SPAS-15, or siaga....or....or (lol)

[MDK_Marshal]

Hmm.. Well, I'll be using 0.12's with this kind of set up, and probably in CQB, so, meh to a realistic spread! I'd be wary of having it in full auto myself... Simply because loading three rounds at a time could make for some interesting mis-feeds if something goes wrong, or if the whole thing just cycles too fast!

[dliberty]

seems reasonable but i have a few points, first iv never been able to put .12 gram bbs in my gun, they always jam and iv heard your not suposed to use them in aegs at all. and second it seems like when the first bb of the set goes in it will block the other two from coming in as theres nothing to push it slightly forward except the bbs underneath it and theres no gurantee that will happen. this project may end with some nasty jams.

[MDK_Marshal]

First off - marui 0.12's. Decent quality BB's, Just lightweight. Problem of bad ammo solved.

 

Second - The loading action is as follows:

 

Air Nozzle goes back

BB appears in between air nozzle and hop rubber

Air nozzle pushes BB into hop chamber

Air nozzle goes back

BB appears between air nozzle and hop chamber

Air Nozzle Pushes BB into hop chamber, moving the BB already in there forwards

Air nozzle goes back

BB appears

Air nozzle pushes Final BB into hop chamber, forcing the other two forwards

Gun fires all 3 BB's

Go to top and start again!

 

 

So, uh, They should all feed fine... Just the same as normal operation, but the tapet cycles three times.

[Stealthbomber]

You haven't thought your feeding system through.

 

Fitting three nubs to the sector gear won't make the nozzle cycle 3 times. It'll just hold it open longer in a single cycle.

 

The key thing is the hop-up chamber. Modify this so it'll accept 3 BBs and you'll probably find that you barely need to modify the sector gear at all. ICS MP5s feed 2 BBs just fine if you back the hop-up off.

 

If you really want the ability to cycle the nozzle 3 times before the gun fires you need to come up with an entirely new gearbox design that has another gear running off the sector gear with a 3:1 ratio.

 

If you drill and tap the sector gear and fit more nubs then I'd suggest fitting the new nubs close to the existing one, just to hold the tappet plate back for an extended period. There's certainly no point in spacing them out around the sector gear.

 

Alternatively, consider either buying, or making, one of those camel-shaped tappet timing thingies. LINK

[ED-SKaR]

no! turning the hop off is a silly way of doing it because its just too erratic.

 

If the nubs are far enough apart then the nozzle will return to the forward position before the second nub engages, thus loading multiple rounds.

[bullzebub]

3 nubs and a slight mod to the tappert plate will do the trick(you want the tappert to be more aggressive and open faster)... it has been done you know :-)

[MDK_Marshal]

Ed And bullzebub have the idea I'm after - If there's enough room, I'd have the nubs spaced out far enough to let the tappet cycle properly - But, I probably would need To mod the tappet to allow it to work correctly.

 

However, I May well have to accept the fact that It won't cycle properly. Only one way to find out! And I have a spare sector gear arriving soon.. all I need is a tapet plate to modify and I can make a test gun!

[Stealthbomber]

Ed And bullzebub have the idea I'm after - If there's enough room, I'd have the nubs spaced out far enough to let the tappet cycle properly - But, I probably would need To mod the tappet to allow it to work correctly.

<{POST_SNAPBACK}>

You guys just don't get it do you?

 

You CANNOT make the tappet plate move backward and forward 3 seperate times in one single rotation of the sector gear simply by installing 3 nubs on the sector gear.

 

You might achieve this by savagely reprofiling the tappet plate but that would probably result in 3 incredibly quick movements, none of which would allow a BB to feed.

 

Think about it. You have 180° to play with. Not 360°. Currently, 1 cycle of the nozzle takes about 120°.

There is NO FREAKING WAY you can design a sector gear and tappet plate that can cycle in 45° of rotation AND still hold the nozzle open long enough to feed reliably.

 

If you think otherwise then please post drawings along with your next post to avoid wasting everybodies time.

[MDK_Marshal]

once again my project is shown the harsh face of reason.

 

Ah well.

 

I guess that just gives me more of a reason to buy a Mad Max shotty

[Stealthbomber]

TBH, I reckon it's still a good idea.

 

Allow me to tell you how it works in my little head:-

 

The BB pops up out of mag and sits in front of hop-up housing, trapped by the sealing face of the hop-up sleeve. The nozzle then moves forward and pushes the BB into the hop-up chamber and then, almost immediately, the piston twangs forward and the gun fires.

 

The problem is that, to chamber 3 BBs at once (properly), you'd have to make the space in the hop-up 12mm longer so there's be room for 3 BBs.

You'd also have to have to alter the nozzle so it moves almost an inch further than it currently does.

Probably not gonna happen.

 

The reason ICS MP5s double-feed is cos the seal at the front of the hop-up sleeve isn't very tight and a BB can squeeze past it without the help of the nozzle. The first BB is stopped by the hop-up and a 2nd BB moves up behind it. The 2nd BB is then loaded by the nozzle and both are fired.

 

What you'd need to do, to make this work, would be to adapt the hop-up assembly, as you say, so that 3 BBs can go in and be held back by something like an O-ring.

You'd then need to trim the seal at the rear of the hop up sleeve so that BBs could move up and into the hop-up chamber without the help of the nozzle.

You'd fit another nub to the sector gear (or fit the camel-thing) to extend the time the nozzle is open a bit longer.

 

So then you'd have 3 BBs moving into the hop-up by themselves, the nozzle moving forward and probably not making an idea seal and the gun firing.

Given that it's a shotty, the lack of perfect seal wouldn't be a big deal. You could actually fit a stronger spring to compensate for any air leak in the hop-up.

 

Actually, one thing that just stuck me, that could be pretty dangerous, is that I've noticed that BBs often shatter when they're double-fed.

Feeding three BBs down the same barrel could cause a lot of shattered BBs and sharp fragments getting launched out of the gun.

TBH, I reckon this might actually be the biggest problem with this idea. Sorry.

[bullzebub]

You guys just don't get it do you? 

 

You CANNOT make the tappet plate move backward and forward 3 seperate times in one single rotation of the sector gear simply by installing 3 nubs on the sector gear.

 

You might achieve this by savagely reprofiling the tappet plate but that would probably result in 3 incredibly quick movements, none of which would allow a BB to feed.

 

Think about it. You have 180° to play with. Not 360°. Currently, 1 cycle of the nozzle takes about 120°.

There is NO FREAKING WAY you can design a sector gear and tappet plate that can cycle in 45° of rotation AND still hold the nozzle open long enough to feed reliably.

 

If you think otherwise then please post drawings along with your next post to avoid wasting everybodies time.

<{POST_SNAPBACK}>

 

strange... since it has been done? after all .. the nozzle doesnt have to seal on the 2 first BBs.

in fact it just have to push the BB 1-2 mm forward if you have a strong magazine spring.

 

and actually you do have more than 180 degrees to work with. the only important thing is that the nozzle is in the front position when the piston starts to move forward.

 

http://www.red-alliance.net/phpBB2/viewtop...t=2963&start=30

[Stealthbomber]

http://www.red-alliance.net/phpBB2/viewtop...t=2963&start=30

<{POST_SNAPBACK}>

Oh yeah!

 

Deedee has always been a reliable source of good information.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

BWAHAHAHAHAHAHAHAHAHA!!!!!!!