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Johnson SMG speargun parts needed

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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Mike_Islandhopper

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Nov 7, 2021
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A buddy just bought a 1972 Johnson SMG Mark II double shot speargun and wondering if anyone knows where I can get ammo, I think purple and green cartridges as well as parts, maybe some tips. I am in Port St Lucie, FL.
 
Those spearguns are illegal in my country unfortunately, however I’d try the companies in your country which sells supplies for tranquilliser projectors. US made pneudart still use various power 22 blanks in some of their projectors & these should be very similar if not the same as what was supplied with that speargun. Ramset blanks could work if you were desperate but may not have the same quality control as the charges for dart guns.
 
Reactions: Mike_Islandhopper
No ammo, but seems to be available thru large box construction stores. I bought as a wall hanger but no reason to believe it is not fully functional. Nothing missing, cracked, chipped, or broken. $350 which includes shipping in the 48 states. PayPal ready. Located in Indiana. Can’t get pictures to load. Please pm and I will be glad to send. Thanks for looking.

https://www.mybalancenow.buzz/
 
The main problem with providing appropriate ammo is the plastic sleeve that holds the ramset rimfire cartridge and the tail end of the spear and which also provides an air space for the cartridge to fire into. Cartridges firing directly into water don't develop enough power, the explosive generated gas needs that expansion gap. This schematic shows the SMG ammo and the gun’s revolving breech.

This photo shows SMG ammo and the plastic cases. Each shot destroyed the cases, you threw them away and chambered a new one.

The problem with the SMG was you could only carry so much ammo and the rounds were easy to drop if you had a case of fumble fingers. On the multi-barrel guns you had to revolve the breech for the next shot after recocking the firing bolt. It all seems a good idea until you use one in the heat of battle.
 
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Hi, can you email me at malv1265 at g mail ... Mike
 

Thank you very much for the information, super helpful. Any idea how I can find or substitute the plastic sleeve that holds the ramset rimfire cartridge? Or am I out of luck? Mike
 
The lack of plastic "Sub-Ammo" sleeves has sidelined those SMG guns for decades, the guns first appeared in the late sixties and had about a decade or so of use before they became orphans. Tapmatic Corporation sold the tooling and parts to a New Zealand company that produced some guns probably from the stock of parts that they acquired as part of the sale. I assume part of the sale was the tooling for the sleeves which are more than just a simple tube. They are sealed at either end and also hold the spear in the gun. If someone wants to get these guns back into action the best approach would be to find that tooling and have more sleeves manufactured. Failing that you need one for a sample to replicate, they do exist, but are held for "museum" purposes. However being banned now in most countries and forbidden for use in obtaining spearfishing records as muscle power is considered the only legitimate means for spear propulsion such an endeavour would not be a commercial proposition.

This is why SMG guns appear to have had little use when sold on places like eBay, their owners ran out of ammo or were soon to do so and decided to sell off the gun before it became totally useless except for a wall hanger.
 
Thank you once again for the detailed information! My friend loves these SMG spearguns and fond memories from 40 yrs ago. I know he would want to play around with getting these guns back into action despite the limitations you mentioned. If by chance this too interests you I'm happy to get on a call and explore this. Curious, how do you know so much about SMG's?
Cheers,
Mike (Florida)
 
I wrote to Tapmatic Corporation years ago and received their brochures when the guns were released, they were printed in red and black. For months the guns had been promoted in Skin Diver Magazine as "SMG day is coming". At that time .22 calibre rifles were not controlled here, nor were shotguns, you could buy and own them without a gun licence. Also spearguns were not regulated in any way and underwater weaponry was basically unlimited. It did not take long to realize that the ammo was going to be a limitation, plus there was no way the guns could be made to be floaters, so I did not pursue importing one. However some guns were imported and I got to see one in a sports store, it was a bit smaller than I thought it would be. I also had made my own Ramset powered spear pistol and found that it was too easy to drop the ammo, so I destroyed it when the regulations changed. Just as well that I never bought a SMG!

A few years ago and well after regulations outlawed all explosive and expellable gas underwater weapons I wrote to Valerie Johnson to find out what had happened with the SMG guns with the view to preserving some of their history. That is when I learned that the SMG product line and everything that went with it had been sold off to New Zealand, but he could not recall the company. He told me that they had a lot of fun with the guns but after 10 years decided to discontinue making them. Tarpoon Diving was one outlet that kept supporting the guns in later years and was a frequent advertiser in Skin Diver with a small block advert.

R.V. Crockett Ltd was the name of the NZ Company.
 
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Another aspect of the SMG is there is no tail stop on the spear. The line slide is tethered by a cable to an attachment position behind the spear tip, so with the gun cocked and ready to shoot you have a cable twisted in a loop at the front end of the gun. Multi-barrel SMG guns shoot free spears out of the other barrels, one often being used for the SMG sleekline powerhead.
 
SUB-AMMO (Instructions)

SUB-AMMO SLEEVES are for use with .22 wadded blanks, Nos. 3 through 6, of the type used in powder actuated tools (manufactured by Ramset Speed Fasteners Company, Remington Arms etc.)

LOAD-YOUR-OWN SUB-AMMO (only)

The blanks are loaded into the cup of the S.M.G. washer and then into the plastic Sub-Ammo sleeves.

For a permanent, waterproof seal apply a liberal coating of clear epoxy or plastic adhesive to the cartridge just prior to insertion. This bonds the cartridge to the plastic sleeve and prevents the possibility of leakage under pressure on deep dives.

SUB-AMMO GREEN for small fish, reef or cave shooting; SUB-AMMO YELLOW for medium fish at moderate range; SUB-AMMO RED for medium fish up to maximum range. Do not use with fibreglass spear. SUB-AMMO PURPLE for large fish at greatest ranges. Do not use with fibreglass spear.

To protect spear head do not use near rocks.
 
Would it be ok for me to email you directly outside this forum? Too bad Australia has become so restrictive. Maybe some of the contacts you referenced would somehow help me figure out how to manufacture the ammo. Also, I am open to explore investing to re-manufacture the SMG gun or something similar since I assume patents have expired. May be worth a phone conversation as well. My email is maLv1265 at g mail dot co m. My name is Mike.
 
Really not much more that I can tell you. Some of the people I contacted in the past are no longer with us, so I cannot be much help there. There is certainly some Sub-Ammo held in private collections and if you look at Spearboard or Scubaboard you will likely find someone who has a sample you could check out.

The US patent info on the cartridge is displayed below. Patent number US3618244A dated 9 November 1971. The patent was applied for earlier and then replaced with a new one, but the date goes back to 26 January 1968. Once you have your patent pending you can start selling your item, you don't have to wait for it to be issued as everything goes back to your priority date.

To replicate the sleeves you need to know the plastic, it may have been polyethylene, ABS or polypropylene, and the various dimensions. A used cartridge and a new one would tell you what you need to know. Plastic mouldings shrink when they cool so that needs to be considered when designing a die to produce the sleeves. It may be worth checking if the tooling exists in New Zealand as it may not have been scrapped, pretty sure R.V. Crockett Ltd is now gone, but some NZ dive shops (long established ones) may have some leads. Tarpoon Diving in Florida may also have some info, this may be them, https://www.tarpoonlagoon.com/, although I don’t remember the exact name.
 
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The SMG relies on the lubricating and cooling effects of water on the barrel, spear and other moving components, so don't be tempted to shoot one on land. This and other warnings are listed on a big red sticker on the gun and are not there for nothing.

CAUTION
1. THIS IS AN UNDERWATER WEAPON.
Treat with respect.
Effective free shaft range exceeds 50 feet.
2. NEVER FIRE GUN IN AIR or snap trigger when gun unloaded.
3. LEAVE BREECH OPEN or barrels rotated to loading position when not in use.
4. DO NOT LEAVE AMMO OR SPEARS IN BARRELS WHEN NOT IN USE.
Rinse in fresh water after exposure to corrosion.
 
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The two barrel SMG had an optional rectangular float unit with rounded ends that was fitted between the barrels to reduce the nose heaviness of the gun to a certain extent. Although multiple barrels seem a great idea they add to the weight in the gun at the front end, especially with all the spears loaded. That is one reason for the double grip handles and the appeal of the gun for scuba spearfishing as the gun was not going to float away after the shot. Nailing someone beyond the range of visibility meant that pulling the trigger in less than perfect visibility was always something that had to be considered and this is probably why the fore grip mounted reel was termed the "safety reel", it having a 50 foot line capacity.
 
Would love to buy a sleeve from someone and 3-d print them. My dad years ago cast one in Stainless Steel but can't seem to find it... he never tried it and might have a problem with the captive air, he's 82. Send me an email at mfriedman1969@yahoo.com
 
Hi Guys, Interesting thread on the SMG spearguns. Hopefully you see my reply on this old post. I have a few of these, and they are really quite neat to use. However I must say there is quite a lot to using them, and worth going over a gun before using it. You can quite easily damage a gun I've found when the breach clearance is incorrect. So to use one it really pays to be an engineering sort.. I'd be interested to speak to those that used them back in the day.

The .22 ammunition you can still pick this up. It needs to be the wadded/paper end charges. The crimped ends are not good to use, there is too much resistance and can mushroom the charge back into the breach jamming the gun. The washers can sometimes be reused, sometimes not, but an item that a patient sort would machine on their lathe. The sleeves I did look at re making however the die cost was very high. Would certainly revisit if anyone else actually wanted these to offset the cost? It would be possible to keep these going but making the sleeve is the hard part purely from the die cost perspective.

Regarding the last comment on the stainless ones. These have to be done quite carefully. I experimented with stainless ones. However there is a lot to making them work, I could write a bit of an essay here, but in short they are just hard to make work in comparison to the plastic ones. Clearance is key considering the charge in the end / where the pin strikes(and no washer to remove that one component), and fit in the barrel. They tend to leak when fired, losing energy (seeping backward to the chamber), and also expand at the end jamming the sleeve in the barrel. Sealing the end could be done in various ways, a sealed paper works however had to be cured/dried in advance which would limit how many sleeves you had for a day out, or sticking the end in some wax, however this also creates issues like the end flaring and so forth / unnecesary resistance. Really the plastic disposable sleeves are the way to go. They seem to seal in the barrel when fired and the charge blasts through the fine plastic layer easily.
 
The SMG sleeves need to be plastic to help seal off the ammo and provide some compliance as they are inserted and also when the expended cartridge is fished out of the breech. The spear tail has to also jam in the nose of the ammo sleeve in order to keep the spear in the gun, so that is why plastic was used, probably polypropylene.

One advantage of using the plastic sleeves was the SMG was not classified as a firearm in the USA because it could not chamber regular ammo and that exploited a loophole in the regulations which allowed it some freedom of action. That technicality did not wash elsewhere and the SMG was considered a firearm right from the beginning, but with .22 weapons considered peashooters they went into the basically harmless category of firearms. However that rapidly changed once mass shootings occurred even though .22 weapons were not involved and the curtain then came down on firearm ownership. Shotguns earned the same fate, with pump action in particular being caught up in compulsory gun buy-backs which effectively disarmed the Australian population.
 
Just to clarify, on possibly my poorly explained last point (haha). The sealing comments I made with the stainless sleeve was 1) you need to seal the end where the spare goes so no water goes in, (also holding the spare in place)and 2. Sealing the sleeve in the barrel. As if it’s not a perfect fit, the energy from the blast tracks backwards towards the chanber, not giving the spear much momentum. Hence plastic works well as when fired the sleeves seems to slightly expand and seal in the barrel allowing maximum energy to drive the spare. The stainless sleeve tends to mushroom at the end as mentioned earlier. Anyway, just some “reading” information for the enthusiasts. Feel free to get in contact if have any specific queries
 
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