Himszy

First of all I would like to say that I have no experience in Warship combat, so comments both postive and negative are welcome.

My Situation:
I am building a submarine, and wish to build a BB gun for it. Now normally when people stick BB guns into subs they have problems with space etc. My sub will be a 1:27.5 (don't ask how I came up with that) Russian Akula II.

This makes the length of my sub 4m long or 12 foot. Obviously with a sub that size weapon choices are endless(well apart from a nuke). Anyway, in short I will be making a BB Gun and missile section and would welcome any advice people would be willing to offer. Work will begin on it early next year.

At the moment I'm wondering about the size of the tube I will use for the barrel of the gun, as I will need something large enough to allow for a 90(ish) degree bend and yet small enough to propel the BB some distance.

The design currently is on a piece of paper soemwhere.....I'll try to scan it in for you later tonight. But how wide does this tube have to be?

I'm sure I'll have lots more questions and you might have some for me......

So comments queries and questions all welcome

Thanks

Michael

black beard

have you acctually started building this model, yet what modeling experience do you have with submarines tell us a bit more about these plans.

Himszy

At the moment I am refitting a HFM Deep Dive with a new Water Tight Chamber and converting a Trumpeter Kilo class.

Once they're at the way I'll be starting on the Akula. Forgot to mention that it won't be used for combat, instead for a project I'm doing involving robots and sensors (the sub is fully automated and will have a form of sonar)

Anthing else you want to know, just ask!

Michael

Captain Nemo12

Michael,

Do you have any details of your Kilo? WTC installations? Or are you just starting out?

Himszy

I've only just got it out the box. WTC will be:
2" acrylic tube with acrylic endcaps, sealed via an axial compressioned o-ring.

Michael

Taxidriver

Its a pity to build a scale Akula (especially one that big) and then stick a gun on it! Why dont build a smaller WWII sub which had a gun? Something like the M1? It had a huge gun for shore bombardment.

Himszy

Before this thread goes any further of topic, does anyone have an answer for my question?

For a BB gun that fires 6mm BBs, what size barrel do I need, bearing in mind it will be bent around 90 degrees?

Then I will answer taxidriver's question.

Mchael

Captain Nemo12

Taxidriver,

There is no need to convince Michael to build a smaller sub! This is not the first time he has heard that comment! (Right Michael?)

Michael,

You should just get a barrel that the BB will fit in, with a slightly larger inner diameter and thin enough so that you could bend it around nicely.

Himszy

Lol, Yup I have heard that before, just a couple of times

Thanks Captain Nemo, I guess the only way to find the exact size is through trial and error.....

Taxidriver, as this project has progressed, more things have been added to it, oringinally there wasn't going to be a BB gun, however as I have alreadly started on the hull, I feel that I should conitinue down that road.

The BB Gun is housed inside the hull in a water tight section when the submarine dives, and it has be designed so it uses existing hull markings, so won't really spoil the appearance.

Michael

Wreno

Not being flip, but it depends on the diameter of your ammunition. BB is a term generally used for .177 ammunition. 6mm, or airsoft, is, of course, 6mm. 3/16" ID tubing works fine for BB's (a bit loose), and 1/4" ID works fine for 6mm. The barrels are availible, with the 90 degree bends in them, for under $10 apiece from the Model Armory and some other sources of Big Gun Model Warship Combat. The ones from Model Armory are snug fitting for 1/4" and 3/16" ammunition, and are made from heavy wall stainless steel tubing. In our sport, 1/4" is generally used for both 1/4" and 7/32" calibers, and 3/16" for both 3/16" and BB calibers.

I just bent a barrel for a test jig from stainless brakeline tubing - seems to work well with 6mm shot in its prototype form. Barrel bending is not simple - there is an art, and it requires special tools and supplies. There are several articles on how to do it, though.

You don't say how you plan to fire the projectile through the barrel. Beware that some localities/countries have laws that can cause you some grief (they would consider it a gun, pretty much regardless of how it is propelled). If that is not an issue, you might want to look in to the already built BB caliber guns made by www.battlersconnection.com.

Hope this was helpful. Good luck, have fun, but be safe.

Wreno

Himszy

Thanks, it was helpful.

I have another question, I do realise that no-one will have an exact answer, but from your experience: How far do you reckon a 6MM Plastic Airsoft BB can be fired by 100psi of compressed air? I'm thinking that it won't be vary far, and so wonder if my design should be changed so the BB can be fired in a straight line maximising distance fired.

Michael

Wreno

Michael,

The lightweight airsoft ammo, good luck on significant range. If you are using airsoft mechanisms, you need more than just luck. Straight of bent barrel makes little difference with a proper pressure gun (it is usually still accelerating around the curve). 65-100 PSI is pretty common in both Small Gun and Big Gun combat. A 1/4" Arizona style gun would work fine for a 6mm, but not for paintballs. For paintballs, you need a closed breech design. You might want to look at some of the Big Gun sites (like www.ntxbg.org) as a starting place for information, there are lots of them out there. You also might want to look at the BigGunsModelWarship group on Yahoo - pretty active.

If you are using your gun mainly for show, not true battling, you can probably use regular 3/8" OD copper plumbing tubing for the barrel - not a good choice for actual combat as it is more susceptible to dents etc., and wil wear out after 10,000 rounds or so. But, cheap, easy to work with.

Wreno

-Inverted-

I'd reccomend using those small 12 gram c02 cylinders, should give the bb nice propulsion.

Wreno

Hmmmm.... 12 gram cartridges....
And you propose to regulate the pressure from a 12 gram cartridge (which has a native pressure of 800 PSI or more) how?
Pierce the end how?
Maintain the pressure over time how?

Also 12 gram cartridges are disposable, one time use.
Is that good for his intended use economically, or would a simple, already available, refillable, one-oz (or smaller) tank with incorporated valve be a better choice?

Don't get me wrong, just trying to figure out why this in particular is your recommendation.

-Inverted-

I dont know, Its talking about BB gun's and Maruzen and Marushin make airsoft guns that run on 12 gram c02 cartridges. If it can shoot a bb out of an airsoft gun it should work with his gun although the pressure would be quite high. You could also use propane or maybe even airbrush propulsion cans. Im not posting on a technical aspect, just listing some ideas for propulsion.

Himszy

Thanks, however I will have compressors onboard (car tire type) and storage tanks, so it seems waste not to use them.

Michael

Wreno

As for the 12 gram cartridges - absent taking a gun already designed for one, and installing it as is (if you can), you might find it technically more difficult than you think in this application. I would note that this is pretty much what the RC Tank guys do with off-the-shelf paintball guns. Keep in mind Michael's application and the size/weight/etc. issues he has to face.

Michael,

Since you are already using a compressed air system, especially with the newer battery chemistry densities, I think you are correct to use your existing compressed air for propellant as well. You might want to look into what is known as the "Arizona" gun. Plain dumb simple, no moving parts other than the poppet valve and actuator. You can eliminate the poppet valve, replacing it with an exhaust valve like the Clippart JEV, and you are good to go (when you drop pressure on the input, it fires. To safe the system, you bleed pressure from the accumulator side.

Wreno