GTA
Airguns by Make and Model => Benjamin Airguns => Topic started by: Robert 5mm on November 26, 2021, 02:01:39 PM
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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)
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Nice results! Well worth the effort! ;D
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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???