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Vacuum Muzzle Options

popgun pete

Well-Known Member
Jul 30, 2008
3,377
744
153
Australia
If a piston is to be used only in a vacuum barrel gun then it does not need the usual gap between the piston nose and the first piston seal as there are no relief ports to bridge across. The shock absorber anvil can then be positioned at only a small gap from the end of the inner barrel tube using a new muzzle with no relief port section and with the forward length of the muzzle devoted to a longer shock absorber if the muzzle is to be the same length as it was before. The working course of the piston will be shorter by the length of the relief port section which will be only about one centimetre.

The "Taimen" does this as it is a pneumo-vacuum gun and not a wet barrel gun conversion, in fact the shock absorber anvil is inside the inner barrel tube and the piston nose never gets to the end of the inner barrel. The anvil and shock absorber are in a sense reversed and "inside out".
 
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tromic

Well-Known Member
Aug 13, 2007
1,615
180
153
Croatia
I made one Delrin_titanium piston few years ago for my Mirage. There is a picture somewhere on this forum.. The mashroom tail had some scratches after I took it out for inspection. Probably that must be some special kind of titanium, heat treated for that purpose ..?
In my first Tomba designs there was no any tilt of the shaft inside the slider or the muzzle posible. Everything was perfectly centered with no loose connections. That perfection made the loading by hands sometimes difficult even frustrating if the shaft were bending during the loading. The solution was to make new Tomba desing: Tomba700X having for a few degrees (2-2.5) tiltable inner part of the Tomba muzzle. I suppose the slider itself in Taimen`s muzzle is also tiltable for some degree.
 

popgun pete

Well-Known Member
Jul 30, 2008
3,377
744
153
Australia
I made one Delrin_titanium piston few years ago for my Mirage. There is a picture somewhere on this forum.. The mashroom tail had some scratches after I took it out for inspection. Probably that must be some special kind of titanium, heat treated for that purpose ..?
In my first Tomba designs there was no any tilt of the shaft inside the slider or the muzzle posible. Everything was perfectly centered with no loose connections. That perfection made the loading by hands sometimes difficult even frustrating if the shaft were bending during the loading. The solution was to make new Tomba desing: Tomba700X having for a few degrees (2-2.5) tiltable inner part of the Tomba muzzle. I suppose the slider itself in Taimen`s muzzle is also tiltable for some degree.
The slider fits snugly into the line slide holder, it is a press fit and held by the "O" ring inside the holder. If you pull off-axis hard enough during muzzle loading then you might bend it and the spear and the instructions specifically tell you not to do so. The chief concern is bending the shaft and putting a permanent bow in it and then you will have problems. There are different alloys and grades of titanium, you need to use the right type for a piston.
loading page.jpg
http://www.supraalloys.com/titanium-grades.php
 
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popgun pete

Well-Known Member
Jul 30, 2008
3,377
744
153
Australia
Thanks Pete!
Taimen is not for careless users...
A "Taimen" is a relatively expensive gun in Russia compared to people's disposable incomes, therefore their owners tend to look after them. Many divers can only afford the traditional forward latching guns such as the RPP models which have all the trigger mechanism located on the outside of the gun body. There are many variations on this theme including friction spear holding mechanism (FZM) guns such as the "Wasp" (photo attached). This type of gun also includes the pistonless guns such as the Vlanik, Evolution and Mavka. The titanium "Taimen" is beyond many who would like the gun, but cannot justify such an amount of expenditure, however the standard model does the same job and importantly floats after the shot.
 
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popgun pete

Well-Known Member
Jul 30, 2008
3,377
744
153
Australia
Maybe there is a business opportunity for a standard titanium piston with a titanium anvil sold as a set that fits all the brands with the same inner barrel diameter. The Omer guns would be the odd ones out as they use an angled face mushroom tail with an unstable sear lever that is blocked by a slide operated by the trigger. The Russian "Seabear" had a titanium piston when it was prepared for selling to the West, but has a front mounted polyurethane shock absorber that was not much good. Better to replicate the current piston shape, however the "ring barked" profile could be used as titanium is way stronger than plastic. The only concern would be if conic friction was a cause of softer titanium wearing at the front of the spear tail socket in the piston nose, the steel pistons being more resistant as they wore spear tails down rather than vice versa. With titanium pistons available plastic pistons could be thrown in the trash where perhaps they should always have been if you want to lean hard on your hand pump handle!

Although I never finished the diagram here is the "Seabear" piston.
View attachment 54370
Finally annotated the piston sketch after working out where all the measurements went. The pointed tail on the spear is cupped by a matching recess in the front end of the piston and they are held together by a polyurethane bush which both parts are jammed into. When the piston hits the muzzle the polyurethane bush acts as a shock absorber and the spear tail pulls free of the polyurethane bush. Note this is not a scale drawing.

PIROMETER SEABEAR PISTON MAK2.jpg

Seabear polyurethane bush.jpg

Seabear polyurethane bush photo.jpg
 
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Diving Gecko

shooter & shooter
Jun 24, 2008
1,410
334
138
Shanghai
Not really sure this deserves its own thread, but Salvi seems to have facelifted the Vuoto muzzles for 2019:

 
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popgun pete

Well-Known Member
Jul 30, 2008
3,377
744
153
Australia
Just comparing the 13 mm versions you can see that the later version is longer.
Salvimar new and older vacuum muzzles.jpg

Maybe they are going to revisit their line slides with more depth in the new muzzle to plug into.
 
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Diving Gecko

shooter & shooter
Jun 24, 2008
1,410
334
138
Shanghai
Just comparing the 13 mm versions you can see that the later version is longer.
View attachment 54641
Maybe they are going to revisit their line slides with more depth in the new muzzle to plug into.
Could be. And perhaps they took a look at their tolerances and the gap between the shock absorber and the inner walls of the rear part of the muzzle. Thing is, I - and at least one other spearo I know of - have busted o-rings on the shock absorber when running +25 bar pressure. This is a problem as the broken o-rings can jam the shock absorber stuck and once that happens, the next thing to break is the piston.
This design is a clone of Dima's UBL muzzles but I have had Dima's up to 35 bar and never ever had a problem with his shock absorbers.

Dima's muzzle also uses the slider to center the shaft in the muzzle and does a good job at that. The Vuoto, from memory, uses the metal washer sitting behind the plastic slider to do the same job - perhaps less precise but probably the easier solution when you are not sure what sliders people will be using.
 
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