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11mm vs. 13mm? (Dry Muzzle, Same Outer Barrel Size)

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

Diving Gecko

shooter & shooter
Jun 24, 2008
1,698
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First, I want to mention that to my experience, there can be no easy loading and a powerful shot. That goes for band guns and pneumatics. Its is just something one has to get used to.
Second, loading effort is calculated like so: 20 atm pressure is about 20.6 kilos per square centimeter. Lets say it is your gun pressure. That, multiplied to the area of the piston, results the loading effort.
So, 20,66*0.949=19,6kilos for 11mm barrel and 20,66*1,326=27.39kilos for 13mm barrel.
So the advantage for 13mm is great power at low pressure, and the gun is generaly not strained. So, add a dry barrel to that, and, wow!

I agree with the math, but I tend to disagree with the real world usage - at least for "advanced spearos".
Allow me to explain as I have had this discussion both here and elsewhere but in short, I think most of us - after a while - load our guns at the pressure that we feel we can comfortably load for a long session of spearing. E.g. my 11mm One Air is loaded to about 29bar whereas my 13mm Seac sits about 10 bar lower. Maybe some beginners just leave the gun as it comes from the factory irrespective of barrel size, I don't know. But to me, it doesn't really make sense to compare guns with different piston diameters while keeping the same pressure.

With a bit more experience since I first started this thread and with the help and input of other spearos here, my conclusion is that there is no real world difference between a 13mm and an 11mm gun if they are both dry muzzled and pressurized to the max loading effort the user can handle.
One thing I do know by now, is that spear thickness and length of the gun plays a big role for me in how much I can pressurize a gun and still be able to comfortably load it.

I have seen some builders/tinkerers say that a 12mm piston is "the best", but I have yet to get an answer to why they feel that is. Maybe they reckon it the best compromise between piston weight, o-ring friction and compression ratio but I don't actually know. Again, in the real world, there is probably very little difference between 11-14mm barrel guns if they are all dry muzzled and all pumped up to have equal loading efforts.
 
marcelo cunha

marcelo cunha

Member
Feb 24, 2017
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I have two pneumatic, seac Asso and salvimar vuoto (90 and 85). I like both very much. One thing that scares me is the loading effort of the salvimar dry barrel. my salvimar is 85 cm but in reality it is 92 cm. I can arm in full mode because I'm used to it and I have a lot of strength. The effort is insane !! I imagine the rifle 120 or 130 cm. Or a person without so much footprint. I load the seac Asso at 18 bar without loader sometimes .
 
Stamatis

Stamatis

Active Member
Aug 29, 2017
122
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I agree with the math, but I tend to disagree with the real world usage - at least for "advanced spearos".
Allow me to explain as I have had this discussion both here and elsewhere but in short, I think most of us - after a while - load our guns at the pressure that we feel we can comfortably load for a long session of spearing. E.g. my 11mm One Air is loaded to about 29bar whereas my 13mm Seac sits about 10 bar lower. Maybe some beginners just leave the gun as it comes from the factory irrespective of barrel size, I don't know. But to me, it doesn't really make sense to compare guns with different piston diameters while keeping the same pressure.

With a bit more experience since I first started this thread and with the help and input of other spearos here, my conclusion is that there is no real world difference between a 13mm and an 11mm gun if they are both dry muzzled and pressurized to the max loading effort the user can handle.
One thing I do know by now, is that spear thickness and length of the gun plays a big role for me in how much I can pressurize a gun and still be able to comfortably load it.

I have seen some builders/tinkerers say that a 12mm piston is "the best", but I have yet to get an answer to why they feel that is. Maybe they reckon it the best compromise between piston weight, o-ring friction and compression ratio but I don't actually know. Again, in the real world, there is probably very little difference between 11-14mm barrel guns if they are all dry muzzled and all pumped up to have equal loading efforts.
Some people I know pump their 11mm guns way more than 30atm, which is the highest allowed (mostly Mares users). Some up to 40atm. Their guns are ok as long as they sevice them yearly. For a 13mm gun there is no need to do that. That is where the difference lies for me. Reliability, operating cost (we do have a depression still here)!
If you do the math, your guns need the same loading effort, so yes of course, if you can load it, you can hunt!
Did I thank you for helping me choose my gun??? thank you!
 
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Diving Gecko

Diving Gecko

shooter & shooter
Jun 24, 2008
1,698
459
188
Some people I know pump their 11mm guns way more than 30atm, which is the highest allowed (mostly Mares users). Some up to 40atm. Their guns are ok as long as they sevice them yearly. For a 13mm gun there is no need to do that. That is where the difference lies for me. Reliability, operating cost (we do have a depression still here)!
If you do the math, your guns need the same loading effort, so yes of course, if you can load it, you can hunt!
Did I thank you for helping me choose my gun??? thank you!

You bring up great points on reliability and operating costs. Also, if only spear on vacations or trips away from home it is not much fun busting a piston or wrecking other parts from possibly running at very high pressures - it might very well ruin your spearing for the rest of that trip.
 
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Stamatis

Stamatis

Active Member
Aug 29, 2017
122
34
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I have two pneumatic, seac Asso and salvimar vuoto (90 and 85). I like both very much. One thing that scares me is the loading effort of the salvimar dry barrel. my salvimar is 85 cm but in reality it is 92 cm. I can arm in full mode because I'm used to it and I have a lot of strength. The effort is insane !! I imagine the rifle 120 or 130 cm. Or a person without so much footprint. I load the seac Asso at 18 bar without loader sometimes .
Hey Marcelo! You make me feel like Hercules because my predathor is at about 22 atm, and it's the 100 (108)! I am not THAT strong man!
 
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marcelo cunha

marcelo cunha

Member
Feb 24, 2017
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Hey Marcelo! You make me feel like Hercules because my predathor is at about 22 atm, and it's the 100 (108)! I am not THAT strong man!
so my gun came with some flaw! 20 bar in the manometer !
 
Jegwan

Jegwan

Well-Known Member
Oct 1, 2012
353
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83
Thanks Jegwan
I have an older Mares MediSten 70 Competiton (seemingly now re-released as the Jet) which would have the 3mm pin and seal.
So would the Sten 11 1.5mm pin and seal fit the older Sten? The new Jet still has the 3mm pin and seal.

I'm not sure about that... Never tried it
Jégwan
 
Stamatis

Stamatis

Active Member
Aug 29, 2017
122
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take a look in my first vídeo with my Asso and predathor . Beginner vídeo !!!!!

Very good Marcello

take a look in my first vídeo with my Asso and predathor . Beginner vídeo !!!!!

Very good Marcelo! I have never seen those fishes before, they dont' live in the mediterranean! And the sea bottom is green?
What is that great beach called? Lovely place!
 
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marcelo cunha

marcelo cunha

Member
Feb 24, 2017
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Very good Marcello

Very good Marcelo! I have never seen those fishes before, they dont' live in the mediterranean! And the sea bottom is green?
What is that great beach called? Lovely place!
Thanks !!! this place is simply one of the sides of copacabana! in this simple place I make incredible fisheries. I can practically see people at the bus stop. I could put videos but the forum is more focused on another type of discussion. I enter the sea by the corner of the beach and swim 400 meters to the point. this small fishes are very valuable , between 6 and 9 usd kg. the bottom is really different from the mediterranean but has a lot of octopus as well.
 
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