Russian "Arma" pneumatic speargun

[popgun pete]

Here is another rear handle pneumatic speargun under development in Russia, the "Arma". In some ways it is similar to the "Pelangas" in appearance with a full length tank tube (32 mm OD) and the plastic handle being mounted on the exterior of the tank rather than forming part of a plastic moulding that serves as the rear pressure bulkhead. The stainless steel inner barrel is 11 mm ID and the gun is intended to shoot either 7.0 mm or 7.5 mm diameter spears.

As with the "Pelengas" the rear metal bulkhead is a turned and machined element that is pinned rather than screwed onto the inner barrel tube, but there any similarity ends. Unlike the "Pelengas" with its "Italian rocker" sear lever pivoting on a transverse pin mounted in the wall of the inner barrel tube, the "Arma" gun uses a reversed sear lever that pivots on a transverse pin located below the inner barrel tube by making use of an asymmetrical inwards extension to the rear bulkhead (a composite photo from the site is attached that shows this layout). Thus the sear tooth is located at the rear of the sear lever and the trigger transmission pin pushed upwards by the usual external trigger lifts the front end of the sear lever rather than its rear end. With this arrangement the mushroom tail on the cocked piston tries to push the sear tooth forwards, but the sear lever cannot turn as the mushroom tail has an extension that also engages a small hole in a rear fitting or bushing inside the inner barrel tube (somewhat reminiscent of the "RPS-3"). The sear lever may also bind on some other hidden feature inside the pivot pin mounting in order to prevent it from turning in that direction, but there are no details.

The advantage of this reversed sear lever layout is that nearly the full length of the inner barrel tube is used for piston travel, the sear lever no longer sits inside the inner barrel tube with only the sear tooth projecting up inside the barrel instead. The disadvantage, if there is one, is that firing the gun rolls the sear tooth rearwards and the tooth geometry on the rear tooth face needs to be such that it does not push the piston backwards against the air pressure trying to urge the piston forwards. That can be achieved by a curved rear face that matches the tooth's travel arc as it revolves downwards on the pivot pin, but only if no component of force is then created that will push the sear tooth downwards as a result of the propulsive force acting on the piston. Usually rocker or "see-saw" sear levers act as hooks, this one acts as a blocking element until you pull the trigger.

This seems to be a novel arrangement for a rear handle pneumatic speargun destined for mass production, hence I thought that forum members would be interested in reading about it.

As is now becoming the fashion in new pneumatic speargun designs the line release is mounted on the side of the gun above the trigger position, but here it is user reversible so that it can operate either on the left hand side or the right hand side of the gun, the line hook on the nose cone being positioned accordingly by rotating the nose cone on the gun with all air pressure released and the muzzle slackened off by a few turns.

The rest of the gun is as would be expected, however it is interesting to see a plastic front-ended, short metal body piston teemed with a metal shock absorber anvil in the muzzle, in my view a much more durable arrangement provided that the impacting faces match.

You can read more about the "Arma" pneumatic gun here: http://apox.ru/forum/topic/12967-pnevmaticheskoe-ruzhe-adept-arma
(All photos are reproduced from this web-site)

 

[tromic]

I like this simple, nice design! Because of having revers trigger also has excellent shooting performance.

http://podvoh.net/forum/avtorskie-ruzhya/149941-avtorskoe-ruzhe-arma-ot-romana-adept6.html#366361

 

[popgun pete]

I made some inquiries about the “Arma” speargun on www.apox.ru and have been helped by “Mechanix” (who is a member here and a knowledgeable contributor on that site) to be able to find “Adept6” (Roman) who was responsible for the “Arma” gun’s design. Roman is an analytical thinker and has much technical information on spearguns at his fingertips in order to provide valuable insights and it is largely thanks to him that the “Pelengas” was finally discussed in a measured manner that allowed me to generate my own thread here on that gun with the aid of his photos from the www.apox.ru web-site.

Unfortunately the financial backer behind the “Arma” project has lost interest in it being a worthwhile investment, at least for the foreseeable future, hence the gun is now in limbo. However all the component parts exist, and so must the engineering drawings and prototype tooling and that means it could be picked up again at some future date. A long stroke gun due to the reversed sear lever it seems to be a better proposition that the (assumed) set back sear lever design used in the LG “Revolution”, but of the latter we need to know more before saying anything definitive. The “Arma” rear bulkhead which supports the sear lever pivot pin (a task normally undertaken by the inner barrel tube) will need to be light for the “Arma” speargun to be a floater, but everything else about the gun seems to be just right and the styling is not unlike the “Pelengas” from the rear view.

 

[popgun pete]

A quick sketch of the "Arma" gun interior demonstrates the relatively unobstructed inner barrel compared with that of say a Mares "Cyrano". In the former only the sear tooth intrudes up into the inner barrel, whereas in the Mares "Cyrano" the entire rocking sear lever sits in the inner barrel as that is where the sear lever pivot pin is located. The increased working course of the "Arma" piston is very apparent in this comparison, it would be about the maximum after allowing space for the inlet valve behind the sear lever position.

 

[popgun pete]

I finally discovered the "Arma"speargun thread where it was first described by Adept6 (Roman) who has created many exciting and innovative spearguns, including this one. This gun is designed in the Ukraine where guns such as the "Pelengas" and the extremely powerful "Aquatech" hydropneumatic spearguns originate from. Correction, it seems Roman is in Belarus and not the Ukraine as I stated in the previous sentence.
https://www.akvalang.com/forum/topic/11824-pnevmat-adept-arma/page-1

 

[Diving Gecko]

Finally a reverse trigger pneumatic...!
I have been thinking about this exact thing for years now. Perhaps I saw this one posted in the past or I thought about it once I started caring more about the best bandguns but anyways, it warms my heart. I even have sketches of exactly the same thing somewhere plus more complicated version of it which would raise the handle. It's such a simple way to gain more "band length" and honestly, I think every new gun launched in the past 5-8 years should have had it. Say, the Evo, Saetta - actually, any gun with a traditional trigger mech. I think the LG Revolution, which was designed from the ground up, doesn't even have it?
As mentioned, I have an idea to take this design a little further, but it may not really work in practice - but it's one of the things I hope to try out in the year to come. I like the simplicity of these triggers more than the valve triggers.

That's a really pretty handle, too. Roman certainly makes/designs nice looking guns. Honestly, I have not really looked much at the Russian guns, but Pete is opening my eyes to them. There is definitely some interesting tech in many of them.

 

[popgun pete]

The reason why the Italian pneumatic guns never tried a different trigger arrangement is that their guns are usually long and the percentage travel gain is therefore small unless a gun is relatively short. In Russia and Ukraine underwater conditions in rivers and lakes are often gloomy with vegetation, algal blooms and swirling silt particles, so their guns tend to be short. A long gun in Russia is generally about one meter or less, say 80 cm, so lengthening the working course of the piston has always been a goal for their designers. However the advantage of the “Arma” gun layout is there is nothing sitting in the inner barrel as the sear lever is pivoted from below the inner barrel, not sitting inside it which affects the airflow. Ironically the only relatively recent change in trigger mechanisms for Italian pneumatic guns was the Airbalete/One Air/Omer XII which reduced the working course of the piston for those guns due to the detachable grip handle hanging off the rear end of the guns.