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 Post subject: 13 cubic Inch HPA Tank?
PostPosted: Sun May 19, 2013 5:34 am 
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The prices I have seen are $69.00 :shock:
http://www.paintballgear.ca/product/Ninja_13Cui_3000psi_-_Aluminum_Tank.html
Image
A comparable size CO2 tanks are $29.00!
http://www.badlandspaintball.com/12-oz-co2-tank.html

If I am going to regulate the QB79 down to 850PSI why not get the CO2 tank? THE HPA tank does have a regulator to bring the pressure down to 850psi.

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PostPosted: Sun May 19, 2013 9:05 am 
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rrdstarr wrote:
If I am going to regulate the QB79 down to 850PSI why not get the CO2 tank? THE HPA tank does have a regulator to bring the pressure down to 850psi.


I could be wrong, but I don't think the Co2 tank can handle the 3000 psi fill like an HPA one. Co2 (whether it's a 12 gram cartridge or a tanker truck full) is pretty much limited to 1900 psi (max) at 120*F, and about 850-900 psi at 70*F. Regulator only affects output pressure, not fill pressure.

I'm sure someone more qualified than me will be along shortly to give you a more detailed answer...


Cheers,
Todd

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PostPosted: Sun May 19, 2013 9:35 am 
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Definitely go with the HPA tank your paying more because of the Reg and you could easily bump the output pressure on the HPA if you wanted too but you wont be able to do so with the Co2.

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Last edited by Ace on Sun May 19, 2013 10:22 am, edited 1 time in total.

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PostPosted: Sun May 19, 2013 10:00 am 
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rrdstarr wrote:
The prices I have seen are $69.00 :shock:
http://www.paintballgear.ca/product/Ninja_13Cui_3000psi_-_Aluminum_Tank.html
Image
A comparable size CO2 tanks are $29.00!
http://www.badlandspaintball.com/12-oz-co2-tank.html

If I am going to regulate the QB79 down to 850PSI why not get the CO2 tank? THE HPA tank does have a regulator to bring the pressure down to 850psi.



also the hpa wont be affected by the temp. like co2 would. as others mentioned, the hpa also give you the option of changing the regulator output later on if you so choose.
GT

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PostPosted: Sun May 19, 2013 10:49 am 
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gt403cyl wrote:
also the hpa wont be affected by the temp. like co2 would. as others mentioned, the hpa also give you the option of changing the regulator output later on if you so choose.
GT


Very true. My reg has been tweaked up to 1200psi (with proper tank block mods) and shoots great.

79 is the second gun down...
Image

Closer view of the tank block mod...
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Shot string...
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PostPosted: Sun May 19, 2013 11:16 am 
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idontknowjack, looks like your block has had some additional pinning to keep it in place for the HPA? Are those screws through the block and tube? Can't see the head of the screw, but they almost look like rivet heads!

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PostPosted: Sun May 19, 2013 11:19 am 
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There is a s.s. solid pin going all the way through the tube, from side to side, between the 2 o-rings of the tank block. There is also a set screw in the top to hold the pin.

From bob's thread here... topic30606.html


Last edited by idontknowjack on Sun May 19, 2013 11:25 am, edited 1 time in total.

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PostPosted: Sun May 19, 2013 11:23 am 
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The CO2 tank is (or should be) rated at 1800 psi, not 3000.... It can be used as an HPA reservoir up to its rated pressure.... but it doesn't have a regulator, so you would have to set the gun up as an unregulated PCP, which can certainly be done.... Assuming that the MSWP stamped on the CO2 tank is 1800 psi, you would likely be able to set the gun up to work from that pressure down to about 1000 psi with a decent shot string.... If you restricted the porting enough, you might be able to use a slightly broader range, down to ~800 psi (maybe)....

The regulated HPA tank will deliver 850 psi from a tank pressure of 3000 psi right down to 850, giving you a constant pressure, and hence the ability to tune for a constant velocity.... That doesn't mean you can use any old hammer strike, it is just as critical to good performance as in an unregulated gun.... Too much hammer strike will result in huge air loss without any increase in velocity, so you still have to achieve a balance....

In addition, you won't find anyone who will fill a CO2 tank with HPA, even to 1800 psi, you will have to do it yourself, with a hand pump or from another tank or ShoeBox compressor.... The regulated paintball tank can be filled at any paintball shop.... DO NOT use any pressure vessel at a pressure higher than that stamped on the shoulder of the tank.... MSWP means MAXIMUM Safe Working Pressure.... Don't arbitrarily decide to use more....

That QB79 tank block in the photo looks like one I have modified, or a copy, with a 3/16" shear pin added, plus an additional 8-32 screw in the top.... If so, it will stand more pressure than you should EVER use in a stock QB79 tube.... The limiting factor should now be the valve retention screws.... Still, I would never run a QB79 tube without a 1.8K burst disc in place to prevent the gun ever seeing more than 1800 psi maximum....

Bob

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PostPosted: Sun May 19, 2013 11:28 am 
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rsterne wrote:
That QB79 tank block in the photo looks like one I have modified, or a copy, with a 3/16" shear pin added, plus an additional 8-32 screw in the top.... If so, it will stand more pressure than you should EVER use in a stock QB79 tube.... The limiting factor should now be the valve retention screws.... Still, I would never run a QB79 tube without a 1.8K burst disc in place to prevent the gun ever seeing more than 1800 psi maximum....

Bob


The tank block mod is not one you did personally, but one you walked me though via PM's (As well as shimming the reg, lol). Works like a charm.


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PostPosted: Sun May 19, 2013 11:29 am 
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Thanks guys!
Sounds like the HPA tank is the way to go regulated down to 850psi. This QB79 is going in an AR207X stock as a cheapie 10m air rifle! Want to get back in it but don't want to fork out $1500+ for a competition grade gun!!!

So with the little Ninja HPA tank, it has the adjustable regulator, I will be good to go!

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Pardini K10
Brocock Concept .22
3 Custom Crosman 2260
Benjamin Discovery .22 w/Joe Hickey stock!
Crosman 150 pistol .22
4 Crosman MK 1 pistol .22
Mrodair CP-1M .22 and .177


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PostPosted: Sun May 19, 2013 11:43 am 
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If you want to keep the gun under 500 fps, you will likely need to REDUCE the regulator pressure by removing one or both of the RED shims (they drop about 150 psi each).... To conserve air, you will also want to reduce the hammer strike, the easiest way is to clip some coils off the hammer spring.... Only a Chrony will tell you what is going on.... Clip a half coil at a time, and have a spare spring as a backup because you WILL go to far.... :mrgreen:

For any given regulated pressure (under 1000 psi in a QB, using a stock spring), you will find that as you clip the spring a bit at a time, the gun will use less air, but the velocity will not drop (or very little).... At some point, the velocity will start to drop, and that is the point where the gun is operating the most efficiently.... Here is an example (at 1600 psi)....

Image

That gun is fitted with an RVA (rear velocity adjuster) which allows you to change the preload on the hammer spring without cutting it.... You can see what happens as you reduce the preload.... Initially the velocity stays the same, then starts to drop.... However, the amount of air used changes drastically even while on the plateau of the velocity curve.... The difference between 2 and 4 turns out on the adjuster is no change in velocity, but the gun uses about half the air per shot.... On that particular gun, I would use 5 turns out, operating the gun on the "knee" of the curve, for the best balance between power and efficiency....

idontknowjack.... You might want to read over this post, and have a go at reducing the hammer strike in your gun.... You are producing 60 shots at ~790 fps with 13.4 gr. pellets (18.6 FPE) for a total of 1114 FPE.... To do that, you are using 3000-1200 = 1800 psi of air (1800/14.5 = 124 bar) from your 13 CI tank, which is 124 x 13 = 1614 CI of air at 1 bar.... The efficiency is therefore 1114 / 1614 = 0.69 FPE/CI.... In a .22 cal QB79, that suggests to me that you may be operating on the plateau part of the above curve, unless the ports are restricting the flow somewhere.... Reducing the hammer spring preload would certainly be worth a try, you may well gain 20 or more shots without losing any (significant) velocity....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


Last edited by rsterne on Sun May 19, 2013 11:51 am, edited 1 time in total.

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PostPosted: Sun May 19, 2013 11:51 am 
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THANKS BOB!
I have seen that chart before. You were explaining to someone else on a different airgun. I will build and RVA for the QB. The QB doesn't really look that dissimilar to the Crosman 22XX.

Already installed my oversized all brass bolt handle(I made three, never anticipating I'd have one myself) on the QB and that makes this cock on closing system much easier!

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Pardini K10
Brocock Concept .22
3 Custom Crosman 2260
Benjamin Discovery .22 w/Joe Hickey stock!
Crosman 150 pistol .22
4 Crosman MK 1 pistol .22
Mrodair CP-1M .22 and .177


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PostPosted: Sun May 19, 2013 11:57 am 
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A conventional RVA on a QB is a lot easier to acheive by removing the pin on the rear cocking block and going to a "cock on open" system.... The (long) screw can be installed off center and simply push on the back of the cocking block to adjust the preload.... It looks like this....

Image

The set screw on the right side of the rear plug pushes on a short plastic rod that acts as a brake by pushing on the side of the adjusting screw to prevent it from turning by itself.... The extra rear notch to hold the bolt back was necessary to give enough loading room with the additional preload I was running.... If you are reducing preload from stock, it is likely not necessary to hold the bolt back....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Sun May 19, 2013 12:03 pm 
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Thanks Bob!
I'll have to pull the QB further apart to find this Cocking block you are talking about to make it cock on open like you suggest AND to make it easier to adjust velocity.

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Pardini K10
Brocock Concept .22
3 Custom Crosman 2260
Benjamin Discovery .22 w/Joe Hickey stock!
Crosman 150 pistol .22
4 Crosman MK 1 pistol .22
Mrodair CP-1M .22 and .177


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PostPosted: Sun May 19, 2013 12:19 pm 
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Here is a thread that needs to be resurrected.... topic43563.html

It gives all the details for converting a QB79 to HPA use as a non-PAL gun.... How does 250 shots per fill sound?....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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