Author Topic: Here's one for you Bob  (Read 248 times)

Alan

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Here's one for you Bob
« on: April 05, 2019, 06:12:48 PM »
Today, I shot 52 rounds and the ending pressure was 2,000 PSI. The starting pressure was 4,400 PSI. The regulated pressure is 1,825 PSI. The pellet weight is 25.39 grains, and the FPS is 880. The bottle is .350 liters. I ran the Sykes calculations, and to me, this looks rather good. Your comments?


  • Roswell, New Mexico
Alan

I have an Omega compressor. If you're a fellow Guild member, and you pass through Roswell, NM, I'll fill your portable tank as a courtesy.

rsterne

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Re: Here's one for you Bob
« Reply #1 on: April 05, 2019, 09:46:05 PM »
FPE is 43.7 x 52 = 2272 FPE....

350 cc / 16.4 = 21.3 CI.... (4400 - 2000) = 2400 psi / 14.5 = 165.5 bar.... 21.3 x 165.5 = 3526 CI....

2272 / 3526 = 0.64 FPE/CI, which is pretty poor efficiency....  :(

I got the same answer using the Sikes calculator....

Bob
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Alan

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Re: Here's one for you Bob
« Reply #2 on: April 06, 2019, 03:54:08 AM »
I must have made a mistake when I entered the data. I'll look at it again.
  • Roswell, New Mexico
Alan

I have an Omega compressor. If you're a fellow Guild member, and you pass through Roswell, NM, I'll fill your portable tank as a courtesy.

rsterne

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Re: Here's one for you Bob
« Reply #3 on: April 06, 2019, 08:15:37 AM »
I'm guessing you have way too much hammer strike, Alan.... What is the plateau velocity with those pellets at that regulator setting.... ie the velocity where increasing the hammer strike won't results in more velocity?.... I'm guessing you are already there.... If that is the case, reduce the hammer strike to drop the velocity down to about 850 fps.... With a little luck, you could double the shot count....

If you need more power, not less, then you need more regulator pressure.....

Bob
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Alan

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Re: Here's one for you Bob
« Reply #4 on: April 06, 2019, 09:50:40 AM »
I will check that. Even if I miss counted the number of magazine loads I used, it couldn't have been more than 2 (16 total shots).
  • Roswell, New Mexico
Alan

I have an Omega compressor. If you're a fellow Guild member, and you pass through Roswell, NM, I'll fill your portable tank as a courtesy.

Alan

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Re: Here's one for you Bob
« Reply #5 on: April 06, 2019, 11:08:17 AM »
My average FPS is 875 ±8 FPS, which is fairly good consistency. The regulated pressure is 1,825, but there is some creep up to about 1,900 after about an hour.

I counted out exactly 75 pellets, and the FPS stayed within the above spec until shot 69 when it dropped to 850. The 75th shot was 644. That's .76 as I recall.

After refilling the gun, I did try to adjust the hammer and pressure, but whatever I do, the velocity drops. This was (is) the same results I got when I first set the gun up. There is no TSS or SGG installed.
  • Roswell, New Mexico
Alan

I have an Omega compressor. If you're a fellow Guild member, and you pass through Roswell, NM, I'll fill your portable tank as a courtesy.