• Welcome to the DeeperBlue.com Forums, the largest online community dedicated to Freediving, Scuba Diving and Spearfishing. To gain full access to the DeeperBlue.com Forums you must register for a free account. As a registered member you will be able to:

    • Join over 44,280+ fellow diving enthusiasts from around the world on this forum
    • Participate in and browse from over 516,210+ posts.
    • Communicate privately with other divers from around the world.
    • Post your own photos or view from 7,441+ user submitted images.
    • All this and much more...

    You can gain access to all this absolutely free when you register for an account, so sign up today!

Frankengun update ....

Thread Status: Hello , There was no answer in this thread for more than 60 days.
It can take a long time to get an up-to-date response or contact with relevant users.


Desk Driver
Dec 6, 2001
A quick update ... well, quickish anyway.

I've been working quite a bit on Frankengun ... Actually built 3 prototypes. The first one I built was the one I wrote of in the other thread ... my 65cm cave-gun, stretched to 75 cm, I rebuilt the whole barrel out of square tubing (easier to work with when you're in a hurry) and made it a rollergun. I also added a sliding muzzle to it - the top guide for the spear (in that case I experimented with bolts between 10mm and 12mm, and between 15cm and 30cm long - the orig 80cm wasn't good enough)

Result? I learnt one or two things about rollers - they're a mission to make just right. They also have to be very straight to work properly. You can lube them with silicon spray, but it doesn't help much. Bearings seize up after water testing - thus no bearings (and there I was thinking I was smart for a change) You also can't make the rollers of metal - they wear too much on the axles.

The sliding muzzle worked very well for my purposes - it is basically a 25mm metal muzzle piece on the front of the gun, with a 20mm pvc conduit running through it. It's threaded at both ends, and a stopper washer screwed on. This stopper is just around the outside of the pvc, it serves to stop the pvc from falling out. When the gun is loaded, the bolt rests on the trigger sear and inside the pvc. When fired, the pvc moves up to the muzzle, slamming into it (and breaking a couple of times as well), but it serves the purpose of guiding the short shaft down the long barrel.

This gun had one huge kick in it - a single 50cm 20mm RA rubber was used, run back about halfway down the underside of the barrel. Drawbacks on this gun was the kick (it kicked more than my 160cm RA - and did a hell of a job destabilizing the shaft), it wasn't extremely accurate like I'd like. But hell, I drove it 10cm into a brick wall. Took me 30 minutes to grind it out (and fix and paint the wall)

Some of the ideas will be carried on to the final Frankengun though - the rollers will definitely feature.

Second gun was a bit of a funny one ... not really a Frankengun per se, but might be one day. It's still not complete, there's SO MANY things to do to it ....

It's also based on the 65cm gun (nice to be able to swap out handle and muzzle - as long as you don't modify them too much) What I did was scrounged around for something stronger to use as a barrel than the normal tubing used - I was planning on putting some serious power onto the gun this time round. Never happened. I kept a 25cm 20mm RA rubber on it. Works pretty well. So, what I found was one of those corner-poles of an office cubicle - those things with 8 grooves on the sides so you can slide in paneling or glass for cubicles ... And .... BRAINFART !!!

Why not build a 'revolver' type gun? So I did. Sorta. I made three spears from 8mm mild steel (I didn't have the time or the spring steel to make proper spears) with wings on the back - one that stands out about 2cm, the others about 1cm each - making 4 wings on the back. This helped guide the shaft through the water - worked like a dream. The barrel was mounted on a 8mm steel rod as well, but not fixed - it can twirl around on it as it pleases. The back end of the rod is welded to a plate, which in turn is welded to a piece of 24mm tube to fit into the handle.

The front of the barrel-rod is threaded (to make things easier for myself) and bolted to another plate. This plate was quite a bit bigger than the back one, as it had to handle a couple of things. It currently has a stub on for mounting the original muzzle, with rubber in place. It also has a locking plate and spring on it - this is just a little see-saw arangement to lock the barrel in place once the right spear is lined up. BTW, all the spears has to fit inside the barrel, and can't be longer than it, because of this plate. It kinda makes sense too ....

This gun was only fired a couple of times, it was more of a toy idea than a real gun in any case. It worked fine, will need some fine tuning to work properly - the locking mech can be improved (it should be coupled with a safety mechanism so that you can't turn the barrel if it's loaded) and the barrel needs some kevlar or delrin washers on the ends. The spears would also need some working on - the cut up the muzzle the first time I shot it, because I assumed (making an A$$ of U and ME) that it would fit. Surprise - it didn't. I've now got a fairly 'open' muzzle on my favourite cave-gun.

The third gun .... now this is where it get's really cool. I've been playing with so many ideas and concepts that I came up with something quite brilliant. I didn't want to damage my RA (too much in any case) and didn't want to do any permanent damage to it. So I set out to build a removable add-on / bolt-on type enhancement to this gun.

What I ended up with, is two pieces of muzzle adapters - the one side bolts inside the original barrel and the other over either the handle or the muzzle. The back part is short - only 2cm stick out when it's in place. The front one is around 10cm long. And quite interesting to boot. It's got rollers - I've put 7mm spring steel axles onto and throught his extension piece, and currently I've got some PVC roller on there - I'm looking for something bad-assed though, like Delrin. Can't seem to lay my hands on any. The two rollers have 'protectors' bolted on as well - these are modified U bolts to keep the rubber from slipping off.

Between the two extension pieces runs a 10mm square rod - solid steel. Onto this I've welded a couple of backwards pointing U bolts - to hook the other end of the rubber. It's threaded on both ends (left and right thread) to make transportation easier.

Result? A bolt-on kit to convert a RA Railgun to a rollergun. Takes about 10 minutes to convert. Nad it whups some serious ass ... I mean, this thing (with the by-now-oh-so-familiar 20mm RA rubbers stretched to 70cm) seriously ROCKS !! I haven't had the heart to shoot it at a brick wall, but I've shot it the original 7mm 1.6m spear straight through a 20mm pine board. I mean, never mind going in and sticking, there was a hole through the board, and the spear was on the other side of the board - the mono got ripped right off the spear when it hit the board.

So ..... to all of the questions out there ... yeah, I'm still working on it. Yeah, I'm gonna sell it. Probably in the next 6 to 12 months. Yeah, it's being patented, so no pictures as of yet.

What have you guys been up to?

I'm getting a bunch of photo's developed on Friday

I hope they can scan them in as well. If not, it'll be another week or so .... grins ....
DeeperBlue.com - The Worlds Largest Community Dedicated To Freediving, Scuba Diving and Spearfishing


ISSN 1469-865X | Copyright © 1996 - 2024 deeperblue.net limited.

DeeperBlue.com is the World's Largest Community dedicated to Freediving, Scuba Diving, Ocean Advocacy and Diving Travel.

We've been dedicated to bringing you the freshest news, features and discussions from around the underwater world since 1996.