Corsair air usage?

[melloroadman]

Bob if you feel up to it and would like to add to your list here are some numbers to play with 155 cc tank.Marvin
.357 Corsair changed hammer spring

.Stock .308 Corsair

.308 Corsair light spring

[rsterne]

HI Marvin....

I don't see the reservoir volume anywhere.... need that to do an efficiency calc....

Bob

[melloroadman]

Bob age must be really getting to you .155 cc LOL.Marvin

[rsterne]

*LOL* didn't see that at the top.... 155cc = 9.45 CI....

Page 1: top row too much variation in fill pressure to do much with....
2nd row: 95 (?) gr. (center 2 strings) 2400 psi fill, 1400 refill = 1000 psi . 14.5 = 69 Bar x 9.45 = 652 CI air used.... 859 fps avg.... 155 FPE x 3 = 467 FPE... 467 / 652 = 0.72 FPE/CI.... 105 gr. @ 808 fps.... 152 FPE x 3 = 457 FPE / 652 = 0.70 FPE/CI

Page 2: I'll do the lightest and heaviest....
81 gr. @ 949 fps = 162 FPE x 5 = 811 FPE.... 3800 psi down to 1000 = 2800 / 14.5 = 193 Bar x 9.45 = 1825 CI.... 811 / 1825 = 0.44 FPE/CI....
117 gr @ 863 fps = 194 FPE x 4 = 774 FPE.... 3800 - 1400 = 2400 / 14.5 = 166 x 9.45 = 1564 CI.... 774 / 1564 = 0.49 FPE/CI

more coming....

Bob

[Butcher45]

It's times like these that you look back on your notes, and say to yourself "I'm glad I recorded the end fill pressures on all those strings, with all of those boolit designs, at all those fill pressures so I don't have to do it all over again now just to get the info I should already have right here in front of me in my notes".  

People almost always include the fill pressure used, but almost always never share the end-of-string remaining pressure.  I am always interested in hearing about the end-of-string pressures in a string, and encourage everyone to record them along with the chrony string fps numbers.

Admittedly, I still forget to record the end fill pressures sometimes.

[rsterne]

Page 3: I'll combine the center two strings on the top row....
81 gr. @ 879 fps = 139 FPE x 10 = 1390.... (2750-900)+(2700-800)=3750/14.5=259 Bar x 9.45 = 2444 CI.... 1390 / 2444 = 0.57 FPE/CI
2nd row, first plus last string....
45 gr. @ 1034 fps = 107 FPE x 10 = 1070.... (2650-800)+(2800-1100)=3550/14.5=245 Bar x 9.45 = 2314 CI.... 1070 / 2314 = 0.46 FPE/CI

Page 4: top row I'll combine the 2nd and 4th strings....
88 gr. @ 871 fps = 148 FPE x 8 = 1185.... (2700-1200)+(2600-1100)=3000/14.5=207 Bar x 9.45 = 1955 CI.... 1185 / 1955 = 0.61 FPE/CI....
bottom row I'll combine the first 3 strings....
97 gr. @ 838 fps = 151 FPE x 12 = 1816 FPE.... (2600-1000)+(2650-1100)+(2700-1100)=4750/14.5=328 Bar x 9.45 =3096 CI.... 1816 / 3096 = 0.59 FPE/CI....

HTHs....

Bob

[melloroadman]

Bob if we take the work load out of this . And look at what air is consumed for a hand pump person we could average the amount of air per shot to Page 1 163 ci page 2 line one 365 ci and line 2 to 391 ci .Marvin

[rsterne]

I agree with your figures for page 2, didn't work through all of page 1.... don't forget that the gun in page 2 is quite a bit more powerful, so you would expect to use more air.... However, the biggest difference in the amount of pumping per shot is because the gun in page 2 is much less efficient.... it only produces 2/3rd of the power per CI of air used....

Bob

[tkerrigan]

The middle and bottom of the third page down, are those round ball or bullets?  Looking good, Tom

[melloroadman]

Bob I understand what you are saying . But these rifles are made like funny cars to get the most power not the most air usage . That is why I want to break this down for others to see that those extra bits of energy can be quite wasteful and create a lot of extra work or driving time to get the tanks filled .Just look at pages 3 and 4 same rifle just tuned different 120-150 ci of air difference per shot . Yes it sounds good to express high numbers in energy . But is all that energy needed most of the time . Look at what NP does with his skill and 22 caliber . Shot placement is the most important thing . But what I have also found is that it is easier and cheaper to lower the power than to try and up the power or caliber .
 The ammo you asked about are bullets that I cast for my self . My Atari is one of them .Marvin

[rsterne]

I absolutely agree that the last bit of power from a PCP comes at a high price in efficiency.... ie shot count/pumping/tank fills.... I find it's FAR better to back the power down a bit and have a quieter gun that gets more shots and frequently better accuracy as well....

A perfect example of this was a regulated .22 cal PCP I was working on about a year ago.... At 32 FPE the efficiency was 0.98 FPE/CI.... At 38 FPE it was 0.84 FPE/CI.... but at 40 FPE it had dropped to 0.59 FPE/CI.... For that last two FPE the shot count dropped from 27 to 18 shots per fill....

Bob