Short question topic

A place for general potato gun questions and discussions.
hectmarr
Sergeant
Sergeant
Argentina
Posts: 1053
Joined: Sat May 07, 2016 3:49 pm
Location: Argentina
Has thanked: 262 times
Been thanked: 261 times
Contact:

Tue Aug 25, 2020 11:48 am

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. :oops: 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? :?
User avatar
jrrdw
Moderator
Moderator
United States of America
Posts: 6571
Joined: Wed Nov 16, 2005 5:11 pm
Location: Maryland
Has thanked: 39 times
Been thanked: 22 times
Contact:

Donating Members

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...
hectmarr
Sergeant
Sergeant
Argentina
Posts: 1053
Joined: Sat May 07, 2016 3:49 pm
Location: Argentina
Has thanked: 262 times
Been thanked: 261 times
Contact:

Wed Aug 26, 2020 8:42 am

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.
User avatar
farcticox1
Sergeant
Sergeant
Posts: 1078
Joined: Sun Mar 31, 2013 12:37 pm
Has thanked: 68 times
Been thanked: 94 times

Fri Sep 04, 2020 2:52 pm

I found the same with steel bbs, different barrels made no difference.
hectmarr
Sergeant
Sergeant
Argentina
Posts: 1053
Joined: Sat May 07, 2016 3:49 pm
Location: Argentina
Has thanked: 262 times
Been thanked: 261 times
Contact:

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 ...
User avatar
farcticox1
Sergeant
Sergeant
Posts: 1078
Joined: Sun Mar 31, 2013 12:37 pm
Has thanked: 68 times
Been thanked: 94 times

Thu May 06, 2021 5:05 pm

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 :shock:
hectmarr
Sergeant
Sergeant
Argentina
Posts: 1053
Joined: Sat May 07, 2016 3:49 pm
Location: Argentina
Has thanked: 262 times
Been thanked: 261 times
Contact:

Thu May 06, 2021 5:40 pm

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.
User avatar
jackssmirkingrevenge
Five Star General
Five Star General
Posts: 26179
Joined: Thu Mar 15, 2007 11:28 pm
Has thanked: 543 times
Been thanked: 321 times

Donating Members

Fri May 07, 2021 10:04 am

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.
hectmarr wrote:You have to make many weapons, because this field is long and short life
hectmarr
Sergeant
Sergeant
Argentina
Posts: 1053
Joined: Sat May 07, 2016 3:49 pm
Location: Argentina
Has thanked: 262 times
Been thanked: 261 times
Contact:

Thu Sep 29, 2022 10:57 am

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!
757_46bc13e157a42.jpg
757_46bc130d76eec.jpg
757_46bc1315f01fc.jpg
757_46bc1321a9989.jpg
User avatar
mark.f
Sergeant Major 4
Sergeant Major 4
Eritrea
Posts: 3627
Joined: Sat May 06, 2006 11:18 am
Location: The Big Steezy
Has thanked: 52 times
Been thanked: 53 times
Contact:

Donating Members

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. :P
User avatar
Moonbogg
Staff Sergeant 3
Staff Sergeant 3
United States of America
Posts: 1733
Joined: Mon Oct 13, 2008 10:20 pm
Location: SoCal
Has thanked: 153 times
Been thanked: 100 times

Thu Sep 29, 2022 5:07 pm

I'll just stick with my bike pump.
hectmarr
Sergeant
Sergeant
Argentina
Posts: 1053
Joined: Sat May 07, 2016 3:49 pm
Location: Argentina
Has thanked: 262 times
Been thanked: 261 times
Contact:

Thu Sep 29, 2022 6:01 pm

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. :P
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 :?
User avatar
jackssmirkingrevenge
Five Star General
Five Star General
Posts: 26179
Joined: Thu Mar 15, 2007 11:28 pm
Has thanked: 543 times
Been thanked: 321 times

Donating Members

Tue Oct 04, 2022 10:03 am

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 :lol:
hectmarr wrote:You have to make many weapons, because this field is long and short life
hectmarr
Sergeant
Sergeant
Argentina
Posts: 1053
Joined: Sat May 07, 2016 3:49 pm
Location: Argentina
Has thanked: 262 times
Been thanked: 261 times
Contact:

Thu Oct 13, 2022 11:30 am

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.
User avatar
jackssmirkingrevenge
Five Star General
Five Star General
Posts: 26179
Joined: Thu Mar 15, 2007 11:28 pm
Has thanked: 543 times
Been thanked: 321 times

Donating Members

Thu Oct 20, 2022 8:50 am

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.
hectmarr wrote:You have to make many weapons, because this field is long and short life
Post Reply