Air use efficiency; Urban 1.5 pumps/shot Bantam .75 pumps/shot
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Air use efficiency; Urban 1.5 pumps/shot Bantam .75 pumps/shot
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Topic: Air use efficiency; Urban 1.5 pumps/shot Bantam .75 pumps/shot (Read 384 times))
Marc In Iowa
Expert
Posts: 1402
God bless us all, everyone
Real Name: Marc
Air use efficiency; Urban 1.5 pumps/shot Bantam .75 pumps/shot
«
on:
December 09, 2018, 11:04:57 PM »
Previously, I've only been able to measure my air use efficiency by how many strokes from my Benjamin pump it took to refill the rifle.
Bantam 177 Hi Lite, GTOs, 900 fps
165 bar->135 (60 strokes to refill)
80 shots
GAMO Urban 22, GTOs, 837 fps
2900 psi->1500 psi (45 strokes)
30 shots
1.50 pumps/shot Urban
0.75 pumps/shot Bantam
The Urban takes twice the pumps.
I see there is a calculator for efficiency:
http://calc.sikes.us/1/
I found this based on another thread here on GTA. I don't understand these measurements so much. If anyone can explain a little of the meaning, I'd be appreciative. 🙂
Since I'm hand pumping, the bottom line for me is how many pumps and how hard those pumps are. Since I got the Bantam (480cc carbon fiber bottle), it's definitely increased my "joy of shooting" as it is so much easier to pump for a nice, long string of 80 shots.
But I'm still interested in what these calculations show.
Logged
USA, Iowa, Cedar Rapids
Until human nature changes, accurate shooting is needed. Please support the CMP mission.
Lead-free plinking (12-85 yds):
- 177 Hammerli 850, COČ w/GTOs
- UTG 10x 44mm
Other rifles:
-Discovery, Urban, Terrus, Bantam
Ribbonstone
GTA Senior Contributor
Posts: 12030
Re: Air use efficiency; Urban 1.5 pumps/shot Bantam .75 pumps/shot
«
Reply #1 on:
December 09, 2018, 11:39:16 PM »
Probably better to figure out the pumps per fill vs. the total energy of the "good"shot count....that would be cloest to "energy in vs. energy out".
Have one .25 that will manage one shot for every 2.8 pumps put in (for 12 shots) but it manages 55 foot pounds per shot. So it's actually 12 shots X 55 foot pounds = 660 foot pounds for 43-44 pumps strokes. Or about 15 foot pounds of energy out for every pump stroke put in.
So basically....think you're looking at 60 pumps in for 80 shots at 12.2 foot pounds (with the 6.8gr. pellets) vs. 45 pumps in for 30 shots at 18.3 foot pounds for the .22's 11.75gr. pellets.
Still a plus for the Bantam...but not as big a plus as just the pump-count would make it seem (.75 to 1.5 seems like a 1:2 advantage.....but 16.2 foot pounds per pump vs. 12.3 foot pounds per pump is more like it..and wiuth a little TLC, can adjust that Urban to be even closer).
«
Last Edit: December 09, 2018, 11:54:34 PM by Ribbonstone
»
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Louisiana
jarmstrong
All American Boy
Marksman
Posts: 488
yes
Real Name: Jack
Re: Air use efficiency; Urban 1.5 pumps/shot Bantam .75 pumps/shot
«
Reply #2 on:
December 10, 2018, 12:59:41 PM »
how many pumps to fill the hose, before the fill check valve opens?
subtract that number from the total pumps to get a true number of pumps actually going in the gun
the hose volume is then dumped with the bleed off
that will change the average pump /shot , to improve the performance of the Urban more than the Brocock
Ya , you still have to pump them strokes to fill the gun, but the gun dose not receive them to aid the shot count
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Smack dab in the middle of USofA
Q
Marc In Iowa
Expert
Posts: 1402
God bless us all, everyone
Real Name: Marc
Re: Air use efficiency; Urban 1.5 pumps/shot Bantam .75 pumps/shot
«
Reply #3 on:
December 10, 2018, 02:12:36 PM »
Quote from: jarmstrong on December 10, 2018, 12:59:41 PM
how many pumps to fill the hose, before the fill check valve opens?
Yup. Got that. Did that.
On the Bantam I start filling at 135 bar and it's 7 pumps. Next time I shoot out the Urban I'll take note of it all when I refill.
I've taken note before but I'll double check and document so I don't have to go from memory.
I'm probably going to tune the Urban up a bit as well (which will make it harder to pump). I think it will likely be more accurate higher than 837 fps, maybe 880-900?
I was using it for Field Target and wanted it under 20 fpe. Not doing that anymore since I have the Bantam.
Logged
USA, Iowa, Cedar Rapids
Until human nature changes, accurate shooting is needed. Please support the CMP mission.
Lead-free plinking (12-85 yds):
- 177 Hammerli 850, COČ w/GTOs
- UTG 10x 44mm
Other rifles:
-Discovery, Urban, Terrus, Bantam
Ribbonstone
GTA Senior Contributor
Posts: 12030
Re: Air use efficiency; Urban 1.5 pumps/shot Bantam .75 pumps/shot
«
Reply #4 on:
December 10, 2018, 06:22:47 PM »
Don't shoot a lot of non-lead pellets, but I did try some non-lead 11.8gr. (old SigSauer pellets) that managed 934fps at about the factory tune setting.
With a little experimenting (so far) seems to have "a thing" for 18.1gr. (lead) pellets when down tuned to something in the 21-20 foot pound area (going to try to refine that a bit).
Logged
Louisiana
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Air use efficiency; Urban 1.5 pumps/shot Bantam .75 pumps/shot