Benjamin 392/397 C9A Valve Mods

[Robert 5mm]

Seeing new posts about the 392 series of Steriod Mods, I thought I would start a new thread to cover some of the topic.
I did not do any mods to pumping linkage other than solid pins.

I had previously posted this old info:

I have a Benjamin 392 and I decided to try doing a valve mod job on my own 392.
I had previously purchased a valve off of Ebay for this purpose so to keep the original as is.
I read all sorts of material and I watched  You-Tube videos,
but did not proceed until reading the 3 easy to do steps posted by TIMMYMAC1.

1) Using a dremel I cut off two to three threads ( 1/8 inch ) from the male end of the inside of valve.
2) I cut off approx 1/4 inch from flat end of the plastic check valve insert.
3) I did not use a #113 O-Ring - I used the original #112 - so I did not lengthen the valve assembly or do step 3.

I also replaced the outside o-rings with square cross-section o-rings from the O-Ring Store - SN70016 and SN70113
I increased volume on my valve and eased the air flow restrictions by enlarging and angling the air path.

Chronograph of after mini_MAC mod

Crosman PHP 14.3 gr pellets
3 pumps – 455 fps
4 pumps – 554 fps
6 pumps – 621 fps
8 pumps – 684 fps (no air left)
10 pumps – 737 fps (a very little air left)
12 pumps – 770 fps (air left)

[35 shooter]

Nice results! Well worth the effort!

[Back_Roads]

 Nice 3 steps should be a sticky
 Now I am curious, Try adding 3 pumps and crony the shot, to see where in the power spectrum it is in with retained air.
Just wondering if there would be a sweet spot where a few pumps would give decent power yet???