SpudFiles

Testing a small hybrid with a 3/16 ", 4.76 mm steel bb, I have the problem of having absolutely no precision when firing the weapon. It works at 9X and the firing barrel is perfectly straight and polished, just like in all my other weapons made the same way. I have not measured the speed but weighing 0.4 grams, it must be very fast. I cannot hit a soup can at more than 3 meters ... and I cannot calibrate the scope open, because the deviation is random, sometimes up, sometimes down or either side ... The barrel is 280 mm long.. Any idea why?

Since you make all the same way, try a barrel from a consistent shooter that you have, so on so forth the process of elimination...

jrrdw wrote: ↑

Wed Aug 26, 2020 4:00 am

Since you make all the same way, try a barrel from a consistent shooter that you have, so on so forth the process of elimination...

I'm going to change the barrel. For some reason, I suspect that the bb`s acquires an energetic rotation movement and that produces the deviation, due to the magnus effect, it is only a suspicion. Thanks for your reply.

I found the same with steel bbs, different barrels made no difference.

A safety valve for pneumatic installation that says 1.8K, how many bar or psi is it? It is a rupture disc of a pressure regulator and I do not understand when it is 1.8K ...

hectmarr wrote: ↑

Thu May 06, 2021 4:49 pm

A safety valve for pneumatic installation that says 1.8K, how many bar or psi is it? It is a rupture disc of a pressure regulator and I do not understand when it is 1.8K ...

kilopascal ? Kpa. 1 Kpa = 0.01 Bar, 0.145 Psi. But 1.8K would be so low

I already understand it. "K" is for multiplying by 1,000.
In this specific case, 1.8K means 1.8 psi x 1000, it is 1800 psi, about 124 bar. Thanks for your answer.

hectmarr wrote: ↑

Thu May 06, 2021 5:40 pm

In this specific case, 1.8K means 1.8 psi x 1000, it is 1800 psi, about 124 bar. Thanks for your answer.

I confirm that is the case, a 1800 psi burst disk is typically one you will find on the exit side of a 850 psi regulator on a paintball bottle. A 3000 psi bottle will typically have a 5K disk, and a CO2 bottle will have a 3K disk.

Looking at info on HPA canisters on the web, I came across this... Apparently I lubricate the threads of the carbon fiber paintball canister with petroleum-derived OIL and not silicone...terrible!

Same thing can happen easier with oxygen tanks, but I probably don't have to sit down and do the chemistry to see how much of a few grams of petroleum grease can do in a sealed oxygen rich environment, even if it is an HPA tank.

I'll just stick with my bike pump.

mark.f wrote: ↑

Thu Sep 29, 2022 5:02 pm

Same thing can happen easier with oxygen tanks, but I probably don't have to sit down and do the chemistry to see how much of a few grams of petroleum grease can do in a sealed oxygen rich environment, even if it is an HPA tank.

No, numbers are not required. With the photos, for me, it is more than enough.
And as for what you think, friend Moonbogg, sometimes I think the same

Moonbogg wrote: ↑

Thu Sep 29, 2022 5:07 pm

I'll just stick with my bike pump.

If you combine high pressure with flammable solvents that will just make the explosion take longer

What do you think... can it take a lot of speed out of a cup-type pellet, have moisture in the barrel at the time of the shot? It is a 24" .22 caliber barrel with 12 microrifling.
It's not water, but if I pass a cotton ball through the inside of the barrel, it comes out quite wet. I have noticed variations in the exit velocity of the pellet after firing several times, it decreases. It is a hybrid weapon that burns butane and compressed air.

hectmarr wrote: ↑

Thu Oct 13, 2022 11:30 am

It's not water, but if I pass a cotton ball through the inside of the barrel, it comes out quite wet.

Putting some water in a sound suppressor to enhance the effect is a well-known trick for firearms, the fluid helps to cool the hot gasses and thus lowers the pressure. I would not be surprised if it is a factor here too, heat is certainly important and even HGDT makes a difference between "insulated" and "adiabatic" chambers when calculating power.