PCP Refill Questions???

[30-06]

Good evening GTA members. I have finally moved over to the Darkside and bought a "tuned" BAM50 with custom MuzzleBrake.(Legal in South Africa)

I have some quetions regarding the filling prosedures?? This is my first PCP so i am allowed to ask some Stupid questions. LOL!!! i can get my hands on a 12L 232 Bar scuba tank and i want to know the following: Do you shoot intil the gun is completely empty and refill, or do you charge it half way through?? At what pressure do you recharge?? How many fills( after initial full charge) will the 12L 232bar tank give me on the Bam 50 before i have to top up the scuba tank??  At what pressure do i top up the scuba tank??

I have got a refill adapter with a pressure gauge.

Did i cover everything?? Anything left to ask?? More info would certainly be appreciated.
One more thing: do you use pellet lube(napier pellet lube ) if you shoot a pcp rifle??

Thanks guys!!

Johan

[johncedarhill]

My solo and Air force are filled to about 200 bar. I think the customary refill point is when the POI starts to change dramatically. Halfway is probably fairly close. If you go to the Airhog.com I believe you will find a calculator to give the approximate number of fill for a tank.  You can play around with the numbers. You will need to covert L to cu feet which I don't recall what that is right now.  You will also need to know the volume of the PCP in cc.  I would be curious how you like the BAM B 50 and B51. THis one might end up on my list of owning more guns than I can use LOL.

[30-06]

Thanks John!, i'm currently trying to find out the tube volume on the BAM50. Waiting for the local forum guys to respond. Theres quite a few Bams around in my Country. Somebody is bound to respond. If i have the info i will use the Airhog calculator.

Thanks again
Joahn

[spysir]

First if you havent already go to the "library" link of this forum:   http://www.gatewaytoairguns.com/library/Library_MainPage.htm   and scroll down to technical details for adjusting the B50/51, it's a 3-4meg PDF file, good stuff there!
 I have in my head the airtube is 190cc( I could be way off) with the lighter hammer spring I fill to 2000psi take 30FT shots or 40 hunting shots and refill, an 88cf (sorry dont know metric) 3000psi tank give around 60 fills before I even have to consider getting more air in the tank.  Let us all know how you like it when you get some shooting done.
 Here's a pic of our current Bam50,


 John

[daved]

Hi, Johan,

As someone else already said, shoot 'til your POI starts dropping, usually 30 to 40 shots depending on the rifle.  The B50/51 is rated for a 200 bar/3000 psi fill, but most will valve lock long before that.  An unmodded 50/51 will probably prefer a fill between 2000 and 2500 psi, and refill between 1500-2000 psi.

Are you sure about the size of that scuba tank?  To convert liters to cubic feet, you multiply L x .03531, so 12L is less than 1/2 a cubic foot.  Standard size scuba tank here is 80 cu. ft., x 28.31687 = 2265+ liters.  Tank size on the B50/51 is 196 cc.  Look in our Library under Air Rifle calculators, there's a fill calculator there.

I don't lube my pellets, so I don't have any answers for you there.  Good luck.

Dave

[johncedarhill]

4 L about 4 gallons and a cu ft. has about 7.65 gal as I recalled from 35 years ago--so 1/2 cu ft is about right. I think confusion sets in because 88 cu ft means the volume of air at standard temp and pressure. I might just ball park measure my carbon tank and just see what the approximate outside volume is.

[Rixtrix]

Hi, Johan and welcome. You need to refill your scuba tank when the pressure in the tank approaches the maximum refill pressure you use  on the gun, otherwise you won't get a full, or consistant , fill. My BSA ultra only has a 60 cc airchamber and I believe I get about 20 refills on a 66 cu. ft. fibreglas tank starting at about 4300-4400 psi fuill. ( My hose is too long and I lose about 19 cc of air every time I open the bleed valve to disconnect the fillprobe). I refill the tank when it gets to 3200, and the scuba shop only charges for a top-off instead of a ful tank fill. I only fill the gun to210- 220 bar instead of the 232 max as it has a more consistant shot string when starting at that pressure. If you have a chrony, just shoot until the velocity drops off markedly while recording each shot. There should be a range where all the shots are within about 20 fps of each other, rising slightly from the start and then falling back to the starting point. That's your shot string. Then you can adjust your fill pressure to the pressure that matches the beginning of your string. Also, not just for safety sake, fill the gun as slowly as possible to avoid heat buildup; just barely crack the valve open. This will give a more dense fill while  achieving the same pressure, and more consistancy.

I'm no expert, this is just what I've found out to work for me.

RicG

[30-06]

Thanks for all the replys guys!! I knew that the friendly folks at the GTA would not let me down. I will try and get my hands on a chrony, to determine my shotstring range.Ii'll pop in if ive got some more questions, but i think you pretty much covered it. I just have to get the Litres to CU feet conversion right

Thanks

JOHAN

[Rixtrix]

One liter is about 60 cubic inches, 1728 cubic inches in a cubic foot, so go from there. If you have a tank listed as a 12 liter tank, this is probably the actual volume, which is .416666 cubic feet. I don't know the volume of air one could compress into theis space at 3000 or 4500 psi, but it seems like a fairly small tank.

Also, one doesn't have to have a chrony. Like John stated above, shoot until the point of impact starts to change dramatically, then back up a couple or three shots from that to make up for temperature or refill discrepancies. Same goes for the fill pressure. One might try a 232 bar fill and see if the POI changes  until it settles town to a consistent spot. This is the great fun about airguns, lots of excuses to keep shooing!

Ric G

[Rixtrix]

Did some more figuring. My 66 cuft tank measures about 6" by 16" or about  .26 cu ft. Your tank probably isn't a small one, but a standard 88 cu ft Scuba tank.

Ric G

[30-06]

Does this look like small tank?? It weighs a Ton!!

[30-06]

"So a 12 litre cylinder at 232 bar would hold almost 2784 litres (98 ft³) of air at atmospheric pressure" Quoted from Wikipedia.

So my tank must be a 98 CU feet tankthen!!???

JOHAN

[daved]

That looks and sounds right, Johan, I hadn't included the difference between water (actual) volume vs. compressed gas.  Different standards of measurement, it'll get you every time :-)!  Sounds like your set, go shoot something!

Dave

[30-06]

Thanks Daved and Rixtrix for the replies. I will get my hands on the Bam in about 3 weeks time. Shes still with current owner at the moment.Ii'm trying to do all the "figuring" beforehand, so that i can start shooting immediatly, when i get my new Baby!!

Will post again after i tested the new lady.


Thanks again for the help!!

JOHAN

[Rixtrix]

Sounds like you're all set, Johan. You should get a lot of fills from that tank, so prepare to have a ton of fun. Good shooting!

Ric G