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Airguns by Make and Model => Benjamin Airguns => Topic started by: wll2506 on March 01, 2019, 11:36:35 AM

Title: Benji 392 Transfer Port Opening Size and Other Stuff !!
Post by: wll2506 on March 01, 2019, 11:36:35 AM

My valve port on my 392 is .158 ... what size should I open it to get better air flow, I'm guessing a #18 drill at .1695 as long as the airport in the barrel is the same size. Opening up the valve port if the barrel port is smaller makes no sense.

I'm also compressing the internal valve spring as this thing is a monster, its a miracle any air can get out with a spring this strong. I know with many of the mods the spring tension is greatly reduced.  Should I cut of 3 coils to bring it down a bit ?

I have a new adjustable piston coming from Mac1 that should help a lot too. I'm looking for 16+ fpe at the muzzle, which will give me 12+fpe at 40 yards. I'm looking for a reasonable relatively easy to do power boost.

wll

Title: Re: Benji 392 Transfer Port Opening Size and Other Stuff !!
Post by: a1rgunz on March 01, 2019, 12:01:51 PM

I can't give advice on the TP, as I don't own a 392. I would, however, recommend either a lighter valve spring or cutting the one you have down for better power potential. My 1322 with a 14.6" barrel hits 12 FPE using a light valve spring and a SSG with a flattop piston/valve (slightly hogged out for more volume) and a retained air setup through a stock transfer port. With a properly adjusted pump and a lighter valve spring, the 392 should have no problem hitting the numbers you are looking for. With a retained air tune, you could probably hit those number with fewer strokes between shots as well.

Title: Re: Benji 392 Transfer Port Opening Size and Other Stuff !!
Post by: wll2506 on March 01, 2019, 01:31:29 PM

Quote from: Geo Schoonmaker on March 01, 2019, 12:01:51 PM

I can't give advice on the TP, as I don't own a 392. I would, however, recommend either a lighter valve spring or cutting the one you have down for better power potential. My 1322 with a 14.6" barrel hits 12 FPE using a light valve spring and a SSG with a flattop piston/valve (slightly hogged out for more volume) and a retained air setup through a stock transfer port. With a properly adjusted pump and a lighter valve spring, the 392 should have no problem hitting the numbers you are looking for. With a retained air tune, you could probably hit those number with fewer strokes between shots as well.

Thanks Geo, I'm going to do that for sure when I get my adjustable piston. That way I just open the gun up once to do what I want to do ;-  )

wll