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Vacuum Muzzle Options

Gazz

Well-Known Member
Jun 22, 2005
216
26
118
41
Sydney Australia
Hi Guys,

It has been a while since I last posted.
I have been using the Salvimar Vuoto and predathor Vuoto for a while now and enjoy them both.

But my 2 complaints are 1 the metal parts of the piston can corrode if left for a while unused. This can make the piston sticky and scratch the barrel.

I like the salvimar muzzle as it make loading the 3 raps easy but, the gasket in the muzzle fails too often (I have been through 5 in my 2 guns), getting gaskets seems impossible in Australia.

So my question is, are there better pistion options?

What are the best after market muzzle option? looking for reliability (the old tomba was good, but was a free shaft (no slider).
Are there any new developments thee days?

Thanks Gareth
 

popgun pete

Well-Known Member
Jul 30, 2008
3,377
744
153
Australia
How often do you change the oil in your guns? Over time water can contaminate the oil and the metal in those pistons is behind the "O" ring, so any corrosion is on the oily side, unlike the Seac Sub and Cressi factory pistons where metal projected on the wet side of the "O" ring. One way to ward off corrosion is to pour a few drops of oil in the muzzle during storage. As for the vacuum seals they are expendable, but if you slightly grease the shaft before use, the emphasis is on slight, then the seals have an easier life as long as you don’t drop the gun on the sand.
Pistons.jpg

I should add that the piston has to be pushed back to let trapped water out from around the piston nose and flushed out with freshwater before putting the oil in as the “Vuoto” models don't have muzzle relief ports.
 
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popgun pete

Well-Known Member
Jul 30, 2008
3,377
744
153
Australia
Could you post a photo of the pistons so that we can see the pattern of the rust?

This photo shows some assorted pistons, some don't have a metal shoulder for the "O" ring seat and they should not have rust problems on the body periphery, but water is not normally able to penetrate in this area. If a gun stands on its muzzle in storage, which is the correct way to store a pneumatic gun, some oil will sit on the back of the piston. Over a long period any water in the oil will separate out with the oil sitting on top of the water and that water can then act on the metal parts of the piston.
assorted pistons.jpg

Salvimar keep changing their Race Kit piston, here is the image from the 2019 catalog. Note the annular groove for holding grease has finally disappeared, it has been reduced year by year as in my view it only weakened the piston.
Salvimar Race Kit 2019.jpg
salvimar piston.jpg
 
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Zahar

Member
Jun 3, 2014
96
13
23
55
The technique of the piston structure is at a standstill!
First put the cuff, but it removes oil from the barrel when loading! Lengthen the piston and put 2 oring and between them oil! Lengthen the muzzle under the long piston!
Throw the cuff, shorten the muzzle, shorten the piston and leave 1 O-ring on it! Efficiency will increase, the mass of the piston will decrease! How much can you tread on one place?
 

popgun pete

Well-Known Member
Jul 30, 2008
3,377
744
153
Australia
Short single seal pistons can wobble in the inner barrel during muzzle loading and can momentarily allow bursts of pressurized air to escape. This problem was observed with the first "Sten" models, that is why pistons were lengthened with two seals placed some distance apart in the later versions and the number of seals went up to three with a wiper on the front end of the piston. If the piston can be held on the spear tail with the spear held by a firmly locating line slide in the muzzle then this can prevent the piston wobbling such as is used in the Doroganich guns. Another gun that uses a locating line slide is the "Taimen" with the line slide firmly located by the muzzle. The "Pelengas" guns also use a locating line slide being in some ways a copy of the “Taimen” in this respect.

Plastic pistons have some advantages due to light weight and avoiding corrosion of inner barrels, their main drawback is that they are weak, but cheap to make and only need a lightweight plastic shock absorber anvil to stop them.

The reason why plastic pistons were lengthened is they could use the forward section as a sliding contact on the inner barrel wall and then only have one "O" ring.at the rear. Unfortunately if small sand particles get embedded in the leading edge of the piston they will wear your inner barrel out.
doroganich 50 R.jpg

Taimen bungee.JPG
 
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Diving Gecko

shooter & shooter
Jun 24, 2008
1,410
334
138
Shanghai
The easy answer is a standard Mares 13mm piston. No metal between the two seals and they are very sturdy. I have busted fancy STC pistons and had corrosion on Seac pistons which have that metal lip as well. But I have never had problems with the Mares pistons. Supposedly, this is also the go to solution for the Italian tinkerers once they really crank up the pressures in their guns - no matter what brand of gun they favor.

As for a different muzzle, Tomba has slider versions, too. I haven't tried them, but make sure it's ok to load them with the muzzle submerged.

Personally, I am using UBL from Dima which are immensely strong and the pistons quite optimized in terms of length and weight. But they do use the same gaskets but since I can easily get them in Europe, I don't mind the hassle of having to travel with a few spares.
Thing is, Dima moved to Belize and has only recently been renunited with his machines. So, I don't know how fast he could make parts and/or ship them.
 

popgun pete

Well-Known Member
Jul 30, 2008
3,377
744
153
Australia
Unfortunately Mares have this "ring barked" piston in the later "Cyrano 1.3", hence the "Sten" piston is a better proposition. Just check the match of the piston nose to the shape of the anvil as an even contact over a wide annular band gives the best results. Those little pips on the piston nose are intended to ensure a centralised hit, but I think their effect is minimal except when working the piston up and down prior to any loading as everything is happening much more slowly. Plus the mushroom tails need to be a good match in terms of shank and mushroom head diameters. I guess that it would hoping for too much if manufacturers standardized their pistons and muzzles.
Cyrano 1.3 piston.jpg
 

Diving Gecko

shooter & shooter
Jun 24, 2008
1,410
334
138
Shanghai
Apologies, forgot the existence of the Cyrano piston. I was indeed referring to the Sten piston.


Sent from my iPhone using Tapatalk
 

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.
PIROMETER SEABEAR PISTON.jpg
 
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tromic

Well-Known Member
Aug 13, 2007
1,615
180
153
Croatia
Pete what is the largest tilt angle of the slider in muzzle from the central axle?
And what is the ID of the slider for 7 mm shaft?

54374
 
OP
OP
Gazz

Gazz

Well-Known Member
Jun 22, 2005
216
26
118
41
Sydney Australia
Thanks for the prompt knowledgeable replies.

Pete, i am aware of the storage is greasing advice but i am afraid sometimes the guns are quickly washed put in a corner and forgotten about..
I will post pics of the pistons tomorrow. Where are you buying your pistons from Pete?

I will check out the UBL from Dima.

Tromic do you still make muzzle kits?
 

tromic

Well-Known Member
Aug 13, 2007
1,615
180
153
Croatia
Hi Gazz,
My son Marko still makes them but with titanium slider.
Yesterday we came back from summer holiday. He told me that he had the O-ring on the shaft that he was using a year before too, with Tomba. There was no visible damage on it.
[email protected]
 

Nico66

Member
Jun 6, 2017
47
22
23
32
Fr
Hi,
for your seal issue, you can try the pelengas seals. They are better than the salvimar.

And it is better to use a 7mm shaft: 8mm will degrade quickly the gaskets!
 

popgun pete

Well-Known Member
Jul 30, 2008
3,377
744
153
Australia
Pete what is the largest tilt angle of the slider in muzzle from the central axle?
And what is the ID of the slider for 7 mm shaft?

View attachment 54374
I checked back and I answered this same question here https://forums.deeperblue.com/threads/taimen-russian-pneumovacuum-speargun.82933/page-14#post-966685. I will measure the diameters once I find my digital callipers, right now I have my carbon fiber callipers, which are useless, and have put my metal set in some other place on another job.
 

popgun pete

Well-Known Member
Jul 30, 2008
3,377
744
153
Australia
Thanks for the prompt knowledgeable replies.

Pete, i am aware of the storage is greasing advice but i am afraid sometimes the guns are quickly washed put in a corner and forgotten about..
I will post pics of the pistons tomorrow. Where are you buying your pistons from Pete?

I will check out the UBL from Dima.

Tromic do you still make muzzle kits?
With vacuum muzzle you need to carry out this procedure which was devised for the “Taimen” as it gets rid of the last saltwater in the barrel. Many "Taimen" and “Pelengas” guns only get used in freshwater, so there it is not necessary, although river water and lake water may not be entirely pure for that matter. You only need a cup of freshwater to do it.
Taimen inner barrel cleaning 2A RUS new bush.gif
Taimen inner barrel cleaning 2A new bush.gif

I buy new pistons from Divestock in Estonia.
 
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popgun pete

Well-Known Member
Jul 30, 2008
3,377
744
153
Australia
Hi Gazz,
My son Marko still makes them but with titanium slider.
Yesterday we came back from summer holiday. He told me that he had the O-ring on the shaft that he was using a year before too, with Tomba. There was no visible damage on it.
[email protected]
As mentioned earlier it may be worthwhile Marko making some titanium pistons and anvil sets and sliders. They would have to be better than the plastic units used now which only stem from a period where cost reductions were being pursued in the seventies and metal pistons and anvils were discontinued. All my best guns have metal pistons and anvils built before the silly decision to convert to plastic and with higher gun prices it should be possible. Ring barked plastic pistons have a potential to be snap action, i.e. they snap in two pieces, or sometimes more, if you have been leaning on the hand pump.
 
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tromic

Well-Known Member
Aug 13, 2007
1,615
180
153
Croatia
I checked back and I answered this same question here https://forums.deeperblue.com/threads/taimen-russian-pneumovacuum-speargun.82933/page-14#post-966685. I will measure the diameters once I find my digital callipers, right now I have my carbon fiber callipers, which are useless, and have put my metal set in some other place on another job.
Yes, I forgot that answer. But the tilt degree (2 deg..?) of the slider in muzzle, without shaft is still unanswered.. ID of the slider is not very important, do not waste your time to measure it.
 

tromic

Well-Known Member
Aug 13, 2007
1,615
180
153
Croatia
As mentioned earlier it may be worthwhile Marko making some titanium pistons and anvil sets and sliders. They would have to be better than the plastic units used now which only stem from a period where cost reductions were being pursued in the seventies and metal pistons and anvils were discontinued. All my best guns have metal pistons and anvils built before the silly decision to convert to plastic and with higher gun prices it should be possible. Ring barked pistons have a potential to be snap action, i.e. they snap in two pieces, or sometimes more, if you have been leaning on the hand pump.
Pete, what would be your suggestion about titanium anvil and piston design? Have you any sketch? I do not believe Marko would make that, but who know... I suppose there would be necessary at least two O-rings on the piston to avoid contact of the piston body with the barrel - not to scratch the barrel?
Next the mushroom tail of the piston must be hardened.. Is it possible with titanium? Or to make titanium steel combination? It would be heavier than the plastic piston and more loud on impact with the anvil... Maybe the muzzle should be stronger - heavier too. A lot of problems to solve...
 

popgun pete

Well-Known Member
Jul 30, 2008
3,377
744
153
Australia
The "Seabear" piston is titanium from front to rear and I have used that gun at maximum pressure without damage to the piston (it took both hands to load it!). As for the piston shape I would copy the Mares piston with two "O" rings on a long piston or one "O" ring near the front and a cup seal at the rear. The cup seal flares out with pressure and maintains a seal even if the inner barrel is not perfectly round. Some annular rings could be put in it to minimize weight and fill with grease. The major manufacturers would have done it but for the high price of titanium, although the "Taimen" has a titanium piston. You would need to buy round bar of 13 mm or slightly less of titanium for the pistons and a thicker round bar for the anvils. However to save money I think the anvil could be made of stainless steel as titanium is said to polarize in the presence of other metals and not cause galvanic corrosion.
Taimen piston 2.JPG
spear alignment in muzzle.jpg

The above sketch shows how the spear is prevented from tilting by the socket fit of the line slide in the muzzle and the front cup on the piston. As originally designed the shock absorber was the piston's polyurethane nose (shown in orange) and the annular base of the vacuum cuff, but at my suggestion a polyurethane bush absorber was integrated into the two-piece hub design when the vacuum cuff was isolated from the shock absorber anvil (shown in yellow). Over the years I have had a few design changes built into the current "Taimen", including the new muzzle seen on the titanium version of the gun and eventually to be used on the alloy version.

In order to avoid scratches the titanium would need to be polished on a buffing wheel to remove sharp edges except for the mushroom tail. Another refinement would be to mount a plastic ring at the front as used at one time by Mares and also by Scubapro for the "Magnum". The upmarket "Magnum" never used plastic parts in its high impact areas, they were only changed to plastic for the slightly inferior "Vintair" many years later. At the time of its release the "Magnum" was ne plus ultra in the pneumatic speargun world and priced to match! The plastic rings or bands are cracked to put them on the piston body and have a single longitudinal hairline fracture once closed up and in place on the piston body. The "Magnum" piston is stainless steel and they kept it short to reduce the weight, in titanium which is half the weight you could go a bit longer.
Scubapro Magnum piston.JPG

I have killed lots of fish with my "Magnum 95" and it is my most used pneumatic gun because it has a good handle. In the seaweed jungle, which is like swimming through a floating haystack at times, I use my "Taimen" as you are pushing through strands of vegetation which conceal many other ambush predators looking for smaller fish while I am looking for them. The only downside of spearing in the seaweed jungle is there are at times stingrays in there bigger than me!
 
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