Did more testing on FPS on my Diana. Put some lights on the chronograph and got more consistent readings. 100F yesterday 670 FPS. this morning 60 F. 720 FPS.
FPS TESTING.
- Thread starter DAVEFISHING
- Start date
And it is more complicated than that with some springers. I have one which the FPS climbs when I do back to back shots, and another which the velocity declines when I do back to back shots.
This image is the FPS of a Benjamin Trail NP2 (22 caliber) fired back to back (except the final few shots which had very long pauses between them). Notice the increase in velocity when the shots are one after the other.
Here is a Benjamin Regal II (22 caliber), also with the NP power plant. It declines when you do back to back shots.
This image is the FPS of a Benjamin Trail NP2 (22 caliber) fired back to back (except the final few shots which had very long pauses between them). Notice the increase in velocity when the shots are one after the other.
Here is a Benjamin Regal II (22 caliber), also with the NP power plant. It declines when you do back to back shots.
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A few years ago testing out Dupont Krytox GPL205 as a springer lube relative to "temperature related velocity changes", I also noticed higher readings with lower temps.
The reason for the testing was due to the fact that when my .177 R9 was lubed with "tar" on the spring and molly paste on the piston & factory piston seal my poi shifted about 1" at only 20 yards when a shooting session went from "snow flurry temp" during sight in to upper 50s during a end of a spring field target match.
Several years ago when evaluating the "new to me" Dupont Krytox lube and here is a report of the test.........
*The R9 was stripped of all petroleum based lubes and then I re-lubed all internal parts with the Krytox GPL205.
*This was during winter so I left my .177 R9 in my unheated sunroom overnight with the temp dropping to the mid 20s and as soon as there was enough light I shot a string of CPLs over the chrony recording the velocities.
*The R9 was then left indoors over night and re-chronied the CPL velocity when a gun was warm.
*To my surprise the average velocity variation between the two strings was only 10 fps with the higher velocities shot with a 25 degree gun.
I really don't know the precise reason for this but I'm guessing that since cold air is denser than warmer air the "cold air cocking" was actually getting more molecules in the receiver vs the less dense "warmer air cocking".
Anywhoo.....that little experiment years ago convinced me that "cold air vs warm air" velocities weren't affecting my .177 R9 with oring sealed piston cap and Krytox lube velocities enough to be concerned.
The largest inprovement in velocity consistency was replacing the diesel prone "Tar" and molly paste with non-dieseling Krytox and replacing the factory piston seal with an oring sealed piston cap. When first using an oring sealed cap the HW factory piston seal had a rather thin parachute sealing edge which created a lot of friction when compressing the air. A few years ago HW redesigned their HW95 piston seal to include a thick parachute edge and reduced diameter body to reduce sliding friction. Testing with the new design HW piston seal I found that it's performance was so close to the custom machined oring sealed piston caps I made that it really isn't necessary to replace as it relates to velocity and consistency............
LOL....I still cut oring sealed piston caps for my guns and currently I'm testing a cap made of molly filled 6/6 nylon and size 020 Military spec 75durometer Viton oring lubed with Krytox..
The reason for the testing was due to the fact that when my .177 R9 was lubed with "tar" on the spring and molly paste on the piston & factory piston seal my poi shifted about 1" at only 20 yards when a shooting session went from "snow flurry temp" during sight in to upper 50s during a end of a spring field target match.
Several years ago when evaluating the "new to me" Dupont Krytox lube and here is a report of the test.........
*The R9 was stripped of all petroleum based lubes and then I re-lubed all internal parts with the Krytox GPL205.
*This was during winter so I left my .177 R9 in my unheated sunroom overnight with the temp dropping to the mid 20s and as soon as there was enough light I shot a string of CPLs over the chrony recording the velocities.
*The R9 was then left indoors over night and re-chronied the CPL velocity when a gun was warm.
*To my surprise the average velocity variation between the two strings was only 10 fps with the higher velocities shot with a 25 degree gun.
I really don't know the precise reason for this but I'm guessing that since cold air is denser than warmer air the "cold air cocking" was actually getting more molecules in the receiver vs the less dense "warmer air cocking".
Anywhoo.....that little experiment years ago convinced me that "cold air vs warm air" velocities weren't affecting my .177 R9 with oring sealed piston cap and Krytox lube velocities enough to be concerned.
The largest inprovement in velocity consistency was replacing the diesel prone "Tar" and molly paste with non-dieseling Krytox and replacing the factory piston seal with an oring sealed piston cap. When first using an oring sealed cap the HW factory piston seal had a rather thin parachute sealing edge which created a lot of friction when compressing the air. A few years ago HW redesigned their HW95 piston seal to include a thick parachute edge and reduced diameter body to reduce sliding friction. Testing with the new design HW piston seal I found that it's performance was so close to the custom machined oring sealed piston caps I made that it really isn't necessary to replace as it relates to velocity and consistency............
LOL....I still cut oring sealed piston caps for my guns and currently I'm testing a cap made of molly filled 6/6 nylon and size 020 Military spec 75durometer Viton oring lubed with Krytox..
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I do know that when compared to traditional "molly lubes" that will diesel under pressure, the rather expensive Krytox "space station lubes" are non-dieseling and don't thicken with age. They also don't change viscosity with temperature like petroleum based lubes. Will it make a difference in your Diana, I really don't know!
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