Canadian Airgun Forum :: Pumping Tecnique

I shoot my Crosman M4-177 from a rest ( sturdy ironing board with cushion on top) to about 29 feet. Four pumps does the job for small 5 shot groups. I recently tried to pump with the rifle upside down on my lap with a more comfortable downward pump with left hand as opposed to more tiring right hand pumping with barrel vertical. I soon discovered that the horizontal pumping method was opening my groups so I have returned to the generally excepted way and my good groups are back.

So, is there an explanation for why horizontal downward pumping pressure does not give the same results. Is the air intake process less effective ?

Author:	ten-ring [ Sun Feb 25, 2024 2:10 pm ]
Post subject:	Pumping Tecnique
I shoot my Crosman M4-177 from a rest ( sturdy ironing board with cushion on top) to about 29 feet. Four pumps does the job for small 5 shot groups. I recently tried to pump with the rifle upside down on my lap with a more comfortable downward pump with left hand as opposed to more tiring right hand pumping with barrel vertical. I soon discovered that the horizontal pumping method was opening my groups so I have returned to the generally excepted way and my good groups are back. So, is there an explanation for why horizontal downward pumping pressure does not give the same results. Is the air intake process less effective ?

Author:	Knappr [ Sun Feb 25, 2024 3:44 pm ]
Post subject:	Re: Pumping Tecnique
Quick question. I realize one must cock a pumper first before pumping, that being said are you loading a pellet prior to pumping? If so maybe try just cocking the gun then pumping then loading a pellet and see what happens. Mechanically nothing should effect the gun itself but it may affect the seating position of the pellet. Just a thought.

Author:	ten-ring [ Mon Feb 26, 2024 12:25 pm ]
Post subject:	Re: Pumping Tecnique
ten-ring wrote: I shoot my Crosman M4-177 from a rest ( sturdy ironing board with cushion on top) to about 29 feet. Four pumps does the job for small 5 shot groups. I recently tried to pump with the rifle upside down on my lap with a more comfortable downward pump with left hand as opposed to more tiring right hand pumping with barrel vertical. I soon discovered that the horizontal pumping method was opening my groups so I have returned to the generally excepted way and my good groups are back. So, is there an explanation for why horizontal downward pumping pressure does not give the same results. Is the air intake process less effective ? The only thought I have is that between one second intervals of pumping from horizontal is that some air escapes back out between pumps which results in reduced air captured to produce max. velocity/FPS. If you tried to push a liquid into a horizontal vessel, much will spill out. I may call Oppenheimer or NASA for their opinion

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