How many HPA Shots from a 68cf tank (1200 psi .177 QB78)?

[777funk]

I don't know of a source of HPA air near me. So if I have to make regular trips to get it filled it wouldn't make sense to get a tank. Any idea on approximately how many shots per tank? I also have a Co2 tank so I'd probably use the air for hunting only.

I'm also looking at 48cf tanks since they're less expensive:
http://www.ebay.com/itm/Guerrilla-Air-3000-PSI-HPA-N2-Paintball-Tank-with-Myth-M3-Reg-48CI-Black-/161472379325?hash=item259880f9bd

[Motorhead]

Crunch your numbers here: http://www.calc.sikes.us/2/

[777funk]

Thanks. Looks like a great calculator.
Not sure I understand these variables:

CC of your gun's tank:

Fill the gun to this PSI:

Fill the gun when it gets down to this PSI:


Which are probably needed to come up with the number of shots.

[RatRacer]

What gun do you have?

[Motorhead]

Thanks. Looks like a great calculator.
Not sure I understand these variables:

CC of your gun's tank: Required  How much air does guns storage have ?

Fill the gun to this PSI: Required What is the Fill Too pressure of gun ?

Fill the gun when it gets down to this PSI: Required Pressure where gun to operate w/o a major velocity drop refilled at ?


Which are probably needed to come up with the number of shots.
Need all this data to come up # of shots per fill

[777funk]

I understand that but isn't it just directly connected to the tank/regulator by hose?

I'm new to HPA so forgive me if that's an ignorant question.


If there is a reservoir in the QB78, how would I find the volume? Secondarily, how will I know when it fills itself?

[RatRacer]

I understand that but isn't it just directly connected to the tank/regulator by hose?

I'm new to HPA so forgive me if that's an ignorant question.


If there is a reservoir in the QB78, how would I find the volume? Secondarily, how will I know when it fills itself?

If it's a stock QB78, then it's a ~42cc reservoir. Your fill setup will/should have a gauge in line for reading psi for safe operation.

[777funk]

Thanks. Yes there would be a regulator at the 68cf tank. I'm still a little confused about the gun's reservoir and the "Fill the gun when it gets down to this psi" field in that calculator, shouldn't it just be connected directly (i.e. the gun runs directly from the regulated tank)?

[Motorhead]

Thanks. Yes there would be a regulator at the 68cf tank. I'm still a little confused about the gun's reservoir and the "Fill the gun when it gets down to this psi" field in that calculator, shouldn't it just be connected directly (i.e. the gun runs directly from the regulated tank)?

In such a case, the guns tank is just a BIG PLENUM and shooting it under the regulators set point is not going to happen.
So, Math becomes volume of bottle and pressure it fills too, Regulator set point pressure 

[777funk]

I'm getting more confused by the second... lol.   

But I'm guessing that the math becomes pretty simple at just this... the volume of air that the QB78 accepts for each shot when the bolt is pushed forward = x. This will depend on the pressure since air is compressed.

But finding that volume x ... any ideas there.


After that it would be tank volume = y divided by x. I'd figure on loosing 10%-20% to air leakage when unplugging the hoses and system slop.

[BigTinBoat]

First off you need to see how efficient your gun is. The more efficient the more shots. Also the more power the less shots.

If you take a low base line of 1 FPE/cuin using 8.44g pellets at about 750FPS then you should see about 600 shots. I think this is about how fast a stock 78 will push them at 1200psi.

Once you get all of your variables figured out you can use the below calculator.

http://www.calc.sikes.us/1/index.php

[William]

I'm getting more confused by the second... lol.   

But I'm guessing that the math becomes pretty simple at just this... the volume of air that the QB78 accepts for each shot when the bolt is pushed forward = x. This will depend on the pressure since air is compressed.

But finding that volume x ... any ideas there.


After that it would be tank volume = y divided by x. I'd figure on loosing 10%-20% to air leakage when unplugging the hoses and system slop.

Ok here goes since nobody wants to explain ...

The Gun has a air tank on it (or Tube), you fill it with a certain volume of air up to the recommended max pressure it can safely hold.

Lets use my Disco for an example....

1. The air tube holds this much in Volume ( 126 cc).
2. Max fill pressure is (2000 PSI).
3. Shooting gun down to (1000 PSI ) the refill to 2000 PSI
4. How many shots do you get between 2000 PSI down to 1000 PSI. (20)
5. Pellet weight (14.3)

PSI before first shot =Max air pressure

2000

Enter an integer from 1000 to 5000
PSI after last shot

1000

Enter an integer from 200 to 5000 which is less than the first PSI
Gun tank volume in cc

126

Enter an integer from 1 to 20000
Pellet weight

14.3

Enter an integer or decimal number from 2.1 to 1000
Total number of shots

20

Enter an integer from 1 to 500
Average FPS for all the shots

800

Enter an integer from 100 to 1500 - See more at: http://www.calc.sikes.us/1/index.php#sthash.IYSBUNqB.dpuf

The above tells you how efficient the gun is on air usage.

Now if you have a 68 CF tank, here is how you figure how many fills you get from the tank to the gun, considering it is not tethered to it from a hose.

Tank Fill Calculator and Volume Chart... Link to tank fill chart... http://www.calc.sikes.us/2/index.php


Cubic foot (CF) rating of your air tank (from chart below)

68

Enter an integer or 1-place decimal number from 1.0 to 200
PSI pressure rating of your tank

Choose a value from the dropdown
Actual PSI in your tank

3000

Enter an integer from 500 to 4500 which is less than or equal to the tank PSI rating above
CC of your gun's tank

126

Enter an integer from 5 to 1000
Fill the gun to this PSI

2000

Enter an integer from 500 and 4500 which is less than or equal to the PSI rating chosen from the dropdown
Fill the gun when it gets down to this PSI

1000

Enter an integer from 500 to 4500 which is less than the PSI value above
- See more at: http://www.calc.sikes.us/2/index.php#sthash.x2SFrSjK.dpuf

No. of times you can fill the 126cc gun air tube from a 68 CF air bottle.

73
Tank PSI drop per fill

13.7

+++++++++++++++++++++++++++++++++++++++++++++++

Now that you know how many shots you get from each fill up, which is 73 times. Then you know you get 20 shots per fill up, you multiply the 20 shots times the 73 Fills and you get the total number of shots you can get from a 68 CF tank filled to 3000 PSI. Using a tethered setup and regulated will be more I think depending on how high the regulator pressure is set at.

SO 20x73= 1460 total shots.

You just need to know what size your airgun fill tube is to do the calculations.

Gosh I hope I did ok on the explanations....

Here is another tank fill calculator web page also... http://www.airgunsofarizona.com/Tanks/FillCalc.html

If you have any questions just let me know..

William

[BigTinBoat]

I'm getting more confused by the second... lol.   

But I'm guessing that the math becomes pretty simple at just this... the volume of air that the QB78 accepts for each shot when the bolt is pushed forward = x. This will depend on the pressure since air is compressed.

But finding that volume x ... any ideas there.


After that it would be tank volume = y divided by x. I'd figure on loosing 10%-20% to air leakage when unplugging the hoses and system slop.

Ok here goes since nobody wants to explain ...

The Gun has a air tank on it (or Tube), you fill it with a certain volume of air up to the recommended max pressure it can safely hold.

Lets use my Disco for an example....

1. The air tube holds this much in Volume ( 126 cc).
2. Max fill pressure is (2000 PSI).
3. Shooting gun down to (1000 PSI ) the refill to 2000 PSI
4. How many shots do you get between 2000 PSI down to 1000 PSI. (20)
5. Pellet weight (14.3)

PSI before first shot =Max air pressure

2000

Enter an integer from 1000 to 5000
PSI after last shot

1000

Enter an integer from 200 to 5000 which is less than the first PSI
Gun tank volume in cc

126

Enter an integer from 1 to 20000
Pellet weight

14.3

Enter an integer or decimal number from 2.1 to 1000
Total number of shots

20

Enter an integer from 1 to 500
Average FPS for all the shots

800

Enter an integer from 100 to 1500 - See more at: http://www.calc.sikes.us/1/index.php#sthash.IYSBUNqB.dpuf

The above tells you how efficient the gun is on air usage.

Now if you have a 68 CF tank, here is how you figure how many fills you get from the tank to the gun, considering it is not tethered to it from a hose.

Tank Fill Calculator and Volume Chart... Link to tank fill chart... http://www.calc.sikes.us/2/index.php


Cubic foot (CF) rating of your air tank (from chart below)

68

Enter an integer or 1-place decimal number from 1.0 to 200
PSI pressure rating of your tank

Choose a value from the dropdown
Actual PSI in your tank

3000

Enter an integer from 500 to 4500 which is less than or equal to the tank PSI rating above
CC of your gun's tank

126

Enter an integer from 5 to 1000
Fill the gun to this PSI

2000

Enter an integer from 500 and 4500 which is less than or equal to the PSI rating chosen from the dropdown
Fill the gun when it gets down to this PSI

1000

Enter an integer from 500 to 4500 which is less than the PSI value above
- See more at: http://www.calc.sikes.us/2/index.php#sthash.x2SFrSjK.dpuf

No. of times you can fill the 126cc gun air tube from a 68 CF air bottle.

73
Tank PSI drop per fill

13.7

+++++++++++++++++++++++++++++++++++++++++++++++

Now that you know how many shots you get from each fill up, which is 73 times. Then you know you get 20 shots per fill up, you multiply the 20 shots times the 73 Fills and you get the total number of shots you can get from a 68 CF tank filled to 3000 PSI. Using a tethered setup and regulated will be more I think depending on how high the regulator pressure is set at.

SO 20x73= 1460 total shots.

You just need to know what size your airgun fill tube is to do the calculations.

Gosh I hope I did ok on the explanations....

Here is another tank fill calculator web page also... http://www.airgunsofarizona.com/Tanks/FillCalc.html

If you have any questions just let me know..

William

William,

He doesn't need to know the air tank size of the gun, as he is talking about the total shots of the air in tank, but he does need to know other info that he does not have. If he knows his guns power and efficiency then he can work backwards as I did for him just above your post.

And also he is looking at a 48CI tank not a 68CF tank just a tad difference in those.

[William]

Rob,
I didnt see your post sorry, and the title says>>>   Re: How many HPA Shots from a 68cf tank.

I was not trying to figure what you did which is very helpful.
I was showing him how to enter and explain how to use the Calculators on the web site calculators. I used the Disco as a reference only. As these calculators are for a non-tether PCP Gun.

Thanks Rob for the explanation. Now I believe he has an understanding of what to do on the Calculators and figure it the way you did.
William

[BigTinBoat]

Rob,
I didnt see your post sorry, and the title says>>>   Re: How many HPA Shots from a 68cf tank.

William - no problem - I do know the "new" guys do stuff like CF vs CI we all do (or did it). He mentions 68CF then 48CF, but he is actually referencing a 48CI paintball tank. I think he wants to "tether" to the tank and have a 1200psi output on the regulator.

[William]

Rob,
I didnt see your post sorry, and the title says>>>   Re: How many HPA Shots from a 68cf tank.

William - no problem - I do know the "new" guys do stuff like CF vs CI we all do (or did it). He mentions 68CF then 48CF, but he is actually referencing a 48CI paintball tank. I think he wants to "tether" to the tank and have a 1200psi output on the regulator.

Yea I think he wants to shoot tethered as well, once he figures out your formula on the air used per shot/efficiency he can figure out how many total shots from the tank he wants to tether it too.

Its probably going to be more than a tin full thats for sure!

William

[777funk]

Unfortunately a tin full will be a few settings for me and the kids. The nearest refil station I know of is over an hour's drive. So I was hoping to find a system that will give 1000 or more shots at 800 fps +- 50.

[BigTinBoat]

So I was hoping to find a system that will give 1000 or more shots at 800 fps +- 50.

This will give you all you need with no travel time or gas money. Yuo will even get some exercise.

[777funk]

So I was hoping to find a system that will give 1000 or more shots at 800 fps +- 50.

This will give you all you need with no travel time or gas money. Yuo will even get some exercise.

One of those pumps was the reason I sold my Benji Discovery.
1. It broke regularly and I had to keep fixing it.
2. It's so much easier to just plug into the 20# Co2 and shoot away. My QB78 seems more accurate to boot. I just wish I could hunt with it.

[moorepower]

So is it REALLY 68cf, or is it 68 ci.??