Pneumatic gun with power regulator vs no power regulator

It does make a difference, but not a big one, as air flows from the tank into the inner barrel through the lower slot in the inner barrel which is mainly filled by the sear lever and another hole on top of the barrel which itself is not that large. Plus the sear lever occupies the barrel, so there are flow restrictions even in non-regulator block guns. The plastic grip handle interior also covers much of the rear of the inner barrel.

Releasing valve guns don't have a sear lever sitting inside the inner barrel, so they have better airflow properties.

In the days when pneumatic spearguns all had metal pistons and shock absorber bodies the guns could be made more powerful by improving airflow inside the gun, but I think plastic pistons and shock absorbers put an end to that as they are susceptible to cracking. With the lower mass plastic piston’s introduction the muzzle relief holes were made much larger as the muzzle body suffered lower impacts than with the metal pistons. If the muzzle relief holes were made too big then the metal connecting webs to the muzzle tip may have failed in the past with metal pistons crashing into them. I had older guns start to unscrew the muzzle nose as the pistons hammered them, fortunately you could see the gap and retightened them before the end was blown out of the muzzle. Hence today pneumatic guns are designed to be somewhat self-limiting due to those weaker pistons.

Physics decided everything for Us long ago! The speed of the harpoon is 33m per second! Speed of sound = Velocity of air movement = 330 meters per second! A hole even half the section of the barrel does not affect the piston speed if there is no excess oil in the barrel of the rifle! Learn Physics Friends! All valve guns are based on this!

Zahar said:

Physics decided everything for Us long ago! The speed of the harpoon is 33m per second! Speed of sound = Velocity of air movement = 330 meters per second! A hole even half the section of the barrel does not affect the piston speed if there is no excess oil in the barrel of the rifle! Learn Physics Friends! All valve guns are based on this!

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Please quote exactly where you got this from or elaborate somehow.
I have been looking for an answer to this exact question for a very long time and your answer does not align with the anecdotal evidence from the many people who pull out the power regulator and swear they see quite a bit of improvement.

I have long wanted to find a fluid dynamicist and pick his/her brain on this matter as to them, it's probably a fairly easy question to answer but I have yet to bump into one.

Now, if the question is whether you would want a gun with or without PR (Power Regulator) I would say it depends on your hunting grounds and technique. If you are shooting a big gun in blue water, then no need for a PR and I would personally pull it out. But the last few weeks I have shot a friend's Predathor 100 on the reef and even with the PR bulkhead doing a bit of throttling it's still powerful enough for the fish I can run into here. But having the PR is such a nice feature and the kind that you may not think you need before you have it.
E.g. two days ago, I shot seven fish on the reef, four of them was on full power as they didn't come super close but one of them came right up to me and even though there was water behind the fish, I shot it on low power to have the easy reloading when I surfaced. I also shot two red Googleeye fish in some deep caves. These fish are fairly small but very tasty so I sometimes take them if nothing bigger is around. But they like to stand right next to the wall but with the low power feature I had no problem shooting them up close and still not risk bending the shaft or getting it stuck. With a rubber gun, unless I had air left to unhook one rubber, I wouldn't have shot those two fish.
So, in short, for a reef gun, I would say go with the power regulator

Please quote exactly where you got this from or elaborate somehow.
I have been looking for an answer to this exact question for a very long time and your answer does not really align with the anecdotal evidence from the many people who pull out the power regulator and swear they see quite a bit of improvement.


Practically I got the conclusions from my valve gun * Pike perch *! Theoretical arguments - from the difference between the speeds of sound and the harpoon and the presence of the inertial mass of the harpoon + water + piston!

Differences may be more apparent at lower start pressures as basically it depends on how long the gas takes to refill the back end of the gun. Low power shots start the piston moving at the gun's cocked pressure and the pressure falls away until it reaches a lower value than the gun's start pressure. Full power shots start at the gun's cocked pressure and the piston moves until it stops at the gun's start pressure. Pneumatic guns that have a series of revolving holes to vary gun power have a very small hole to produce a large power reduction.

Zahar said:

Physics decided everything for Us long ago! [...]
A hole even half the section of the barrel does not affect the piston speed if there is no excess oil in the barrel of the rifle! [...]

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This is exactly the rule of thumb I was hoping an engineer in fluid dynamics would be able to give me. I would have explained/shown the layout of a classic Italian airgun and asked something like:
"How much speed/energy would the piston loose with different sizes of air transfer holes (power regulator)?"
Maybe I would ask for losses at air transfer bore areas of 25%, 50%, 75% of the piston size or if he/she ran it through a simulation software it could probably output many more values fairly easily.
In lieu of this, I have been waiting to get back home and find the time to test this. The plan was to 3D-print a handful of bulkheads with different sizes of bores and then shoot penetration tests and possibly measure the speed, too of each iteration. But it's quite a lot of work as the gun would need to be taken apart for each change of bulkhead.

Now, the bore size is 7mm in traditional Italian airguns (bushing design, not Scubapro/Salvimar gasket version*) which in cross area is just 29% of the piston size and as I mentioned many other spearos say that when they pull their power regulator blocks out, they see an improvement. This suggests that a bore of 29% is still limiting the airflow quite a bit. But how much energy loss we are talking, I don't know.

*As for the Salvimar guns (old Scubapro design) they use a plate with a gasket that seals four oblong holes. If I had to guess, I would say the total cross area would be larger than on the 7mm bushings but I will measure it the next time, I take a Predathor apart.

Zahar said:

Please quote exactly where you got this from or elaborate somehow.
I have been looking for an answer to this exact question for a very long time and your answer does not really align with the anecdotal evidence from the many people who pull out the power regulator and swear they see quite a bit of improvement.


Practically I got the conclusions from my valve gun * Pike perch *! Theoretical arguments - from the difference between the speeds of sound and the harpoon and the presence of the inertial mass of the harpoon + water + piston! View attachment 56443View attachment 56444

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This one?

popgun pete said:

This one?
View attachment 56446

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This is the first version without a combat strength controller!

Some years ago I read an article discussing flow restrictions in pneumatic guns. It indicated that flow restriction via hole diameters was less critical with gas than it was with water, such as in hydropneumatic guns where the spear is propelled out of the gun by a moving column of water. It was on a Russian site, but I cannot remember which one. To obtain power reductions by throttling you only need look at the revolving throttle in the Neptune pneumatic gun from Tula to see how small the holes have to be to produce appreciable reductions of power in the shots. The photo below shows the plastic throttle, it has four positions, safe (no hole) and three holes of varying sizes, but here we can only see two of them. The third hole will probably be a pin hole.

The table for the gun shows the effect of the power reducer in the lower rhs.