I'm a casual AP shooter, but i've noticed some odd "not on call" shots. I felt that maybe I was getting inconsistent CA out of my regulator. Results are below.
So I chrono'd my Hammerli 480 after filling it's cylinder and this is what I found.
Begin (165bar)
Shots 1 - 20 Avg fps increase 2 (155 bar)
Shots 20 - 30 Avg fps increase 5 (150bar)
Shots 30 - 40 Avg fps increase 5 (140bar)
Shots 40 - 50 Avg fps increase 2
Shots 50 - 60 Avg fps increase 5 (130bar)
Shots 60 - 70 Avg fps increase 3 (120bar)
Shots 70 - 80 Avg fps increase 1
Shots 80 - 90 Avg fps increase 1 (110 bar)
Shots 90 - 105 Avg fps increase 2 (100bar)
Shot 1 - 105 Avg fps increase 26
Standard Deviation in each group was within the tolerance of the Chrony, so it appears that the only issue is the escalating scale of fps from the beginning to the end.
As a novice, what is recommended? ....
Do I just shoot through it as that fps differential really won't show up on the target, or "wholy crap, throw that Hammerli away and start over with something more consisten over 100 shots?"
AP 26 FPS difference through 105 shots - concern?
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I don't think so. I was training this weekend and kind of 'felt' that my cm162ei had low velocity. Busted out the Chrony (uggghh, always a painful exercise)... 425fps or so. Upped that to 495fps - felt snappier but surprise, didn't have to lower the rear sights. Groups the same (aka, as bad or as well as I can).
Doesn't matter, just go and get your new toy already! ; )
Doesn't matter, just go and get your new toy already! ; )
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RandomShotz
- Posts: 553
- Joined: Sat Dec 04, 2010 5:24 pm
- Location: Lexington, KY
I'm breaking out some Physics 101 that I have not used in a very long time, so feel free to correct my evaluation.
In round numbers and assuming no loss in velocity as the pellet travels down range (a reasonable simplifying assumption for the point of this exercise):
500 fps over 33 ft - time of flight = .066 seconds
450 fps over 33 ft - time of flight = .073 seconds
For a difference in time of flight of .007 seconds.
Acceleration due to gravity = 32 feet/second/second
Increased pellet drop due to increased flight time of .007 seconds = .000784 ft or about 0.24mm
(see: http://www.physicsclassroom.com/class/1dkin/u1l6a.cfm )
There may be an effect due to the motion of the gun under slightly reduced recoil, but that is going to be similarly negligible.
In other words, it's not the gun's fault if you shot a 7.
Roger
In round numbers and assuming no loss in velocity as the pellet travels down range (a reasonable simplifying assumption for the point of this exercise):
500 fps over 33 ft - time of flight = .066 seconds
450 fps over 33 ft - time of flight = .073 seconds
For a difference in time of flight of .007 seconds.
Acceleration due to gravity = 32 feet/second/second
Increased pellet drop due to increased flight time of .007 seconds = .000784 ft or about 0.24mm
(see: http://www.physicsclassroom.com/class/1dkin/u1l6a.cfm )
There may be an effect due to the motion of the gun under slightly reduced recoil, but that is going to be similarly negligible.
In other words, it's not the gun's fault if you shot a 7.
Roger
Thanks Roger, "I guess if it wasn't for science and math, we'd have nothing to proof" ... old calc joke from the 80s.RandomShotz wrote:
In other words, it's not the gun's fault if you shot a 7.
Roger
Actually, it was Rover passing gas three lanes over that made me shoot the 7s....
Thanks for clarifying.