SpudFiles

roboman wrote:Amazing work, Jack! I've always wanted to see someone make a large caliber BBMG-ish gun!

Well, this is still smaller than Brian's efforts here and here.

I'm through with testing this breech for now, next step is to concentrate on tidying up the valve-tank setup, making it a bit more "permanent" now that I've proven it works well. After that I'm free to add on any breech/barrel combination, let the high pressure experimentation begin

You linked to the same gun twice..

I think, because this " research" model goes on where I quit...the barrel must have thought it was on one of my guns and thus it BTB-ed itself...

Seriously though...

I'm very curious where this will lead and what type of bolt set-up you will end up with..

When my bankaccount lets me I'll be back in the game of full auto myself..( Austrian accent)
But I'll try the forced blowback on a blocker bolt with a modded QEV and snapvalve..

I kinda figured you would use the bottom curve as a hook to hang it from your belt...never knew you were so gangsta...
Better order that homey sight too!

Please don't go for the angled stengun appearence...

And you should have linked to the first marble MG
http://www.spudfiles.com/forums/viewtopic.php?t=3313&

oh..the early days..

Brian the brain wrote:You linked to the same gun twice..

Damn, I meant to link to your first one.

I think, because this " research" model goes on where I quit...the barrel must have thought it was on one of my guns and thus it BTB-ed itself...

Seriously though...

Hehe no idea what happened, probably double feed and the second bearing struck the first while still in the barrel.

I'm very curious where this will lead and what type of bolt set-up you will end up with..

I'm quite adamant (after the whole reciprocating piston saga which after all that effort, I lost interest in ) that there should be no moving parts.

When my bankaccount lets me I'll be back in the game of full auto myself..( Austrian accent)

Stop producing low pressure launchers with the wife and the finances will come back

I kinda figured you would use the bottom curve as a hook to hang it from your belt...never knew you were so gangsta...
Better order that homey sight too!

Please don't go for the angled stengun appearence...

Oh Yes, keeping it real

I took apart the handle-bottle connection and rebuilt it, was contemplating using your perpendicular configuration but having the tank in line with the barrel makes it a lot more compact.

Not sure what I'm going to do with it next, maybe just build an ordinary vortex block BBMG in 4.5 or 6mm and see what it can do. After getting impressive results from a BBMG at compressor pressures, I imagine upping the pressure by a factor of 8 will have a devastating effect.

with the wife

or at least not with your own wife

an ordinary vortex block BBMG in 4.5 or 6mm

ohh come one you haven't properly tested this idea yet... I know it's not as cool as the farting machine (even though it has lazzzer sound) but it deserves to be tested thoroughly

Yes...you do that Jack...while I thoroughly test the other wives..

POLAND_SPUD wrote:ohh come one you haven't properly tested this idea yet... I know it's not as cool as the farting machine (even though it has lazzzer sound) but it deserves to be tested thoroughly

When filmed with my mobile everythings gets teh 1az0r 50undz

When I said BBMG I still meant with a detent, just not in this calibre because to be honest the fragility of the slingshot ammunition is quite disappointing.

Yes...you do that Jack...while I thoroughly test the other wives...

Careful with the high pressure testing, remember you can cut through steel with water if its moving fast enough

If it doesn't stretch, it 'll tear...either way is fine with me...


I don't want it back after I shoot it off.


Darn BB's

Brian the brain wrote:If it doesn't stretch, it 'll tear...either way is fine with me...

I don't want it back after I shoot it off.

Back to the subject of this thread, I think I've hit on a way to make a high capacity tube magazine that is still compact and without the hassle of a spring:



One "issue" I can see is that power will increase as the mag empties, because the magazine volume is effectively the chamber it will increase as the BBs are removed. This change in volume will also affect rate of fire as given the same flow from the valve, the pressure will take longer to reach the limit of the detent. The extent to which this will be noticeable is yet to be determined though, methinks a prototype is in order

Won't work well.

If the tube ID matches the BB's closely, you will not get much flow and all the bb's will simply be pushed out.
If it doesn't, there is still a big flow restriction, still possibly pushing out all bb's instead of shooting them. I think the magtube will need to be like ~1,5 times the BB diameter (this also allows more bb's to fit in, double stacked).
The space behind the bb's won't really act as chamber, as the flow restriction is up ahead.

To make it work:
I think you should DEFINITELY add a chamber near the detent, and possibly feed the chamber with a bypass.

psycix wrote:I think you should DEFINITELY add a chamber near the detent, and possibly feed the chamber with a bypass.

This what I was thinking, just before the detent I'll have a section of perforated barrel tube feeding the BBs held within a larger diameter tube as a "chamber", something like this:

jsr;

That looks feasible, just increase diameter like psycix stated.
A tapered shape before the chamber ports.

More ammo and better flow.

I think I'll keep the main tubes at 4.5mm, capacity will be sufficient for my purposes and it will reduce the likelyhood of jams. Steel BBs are 4.4mm so there'll be adequate blow-by to fill the chamber. The chamber section can be a 6mm tube with perforations held within a small section of larger tubing. I'll start making it this evening, hopefully I'm on to a winner

jsr;

An idea I have been toying with, which may have been discussed previously is a helical tube shaped magazine.

Imagine some hydraulic brake line wrapped around a piece of pipe to form it to the shape of a spring. A long length shortened by spiral wrapping.

Just need to find optimum radius of the bend to prevent kinking of the brake line.

A helical magazine would be perfect, it's even used in some firearms like the Calico series or the Bison AK variant (and what do you know, the Chinese are at it too...) not to mention the A-10's massive slugger.

The question is finding the right tubing and having the facilities to bend it, which is the reason I'm going with the inline straight magazine idea.

You don't need tubes to hold the ammo. You can construct all kinds of mag shapes with square shapes too, just round stuff where the ammo goes around a corner.
This might also give you the necessary blowby without putting too much force on the bb's. Remember that they only need to roll to the breech, not get stuffed in there.


You could construct a simple mag out of wood pieces between two plates. Put some epoxy and bolt stuff down to hold it together and seal.