GTA

Airguns by Make and Model => Benjamin Airguns => Topic started by: Wolfer on May 19, 2018, 01:35:11 AM

Title: 392 transfer port size?
Post by: Wolfer on May 19, 2018, 01:35:11 AM

Doing some mods to a 392want to open up transfer port. What would you recommend. I know what I want to try but want other opinions before I tell mine. Also I have angled the port in the past does this mod really add any benefits.    Mike

Title: Re: 392 transfer port size?
Post by: Rob112o on May 19, 2018, 02:19:20 PM

I saw an increase to FPS with the angling to valve opening on my 1322. Which got 505FPS on 10pumps: https://www.gatewaytoairguns.org/GTA/index.php?topic=112378.msg1200899#msg1200899 (https://www.gatewaytoairguns.org/GTA/index.php?topic=112378.msg1200899#msg1200899)

I modded a C9A, the Crosman Blue Streak, did the same angling at the valve opening along with 2 spring mod, bigger middle washer, cutting down check valve, weak valve spring. Here's numbers for that: https://www.gatewaytoairguns.org/GTA/index.php?topic=112378.msg1165452#msg1165452 (https://www.gatewaytoairguns.org/GTA/index.php?topic=112378.msg1165452#msg1165452)

Title: Re: 392 transfer port size?
Post by: RCO on May 20, 2018, 02:12:53 PM

My 392 has a .187 angled port. I stopped modding it at 18.5 FPE as that was more than I needed. The angled port helped with dumping all the air.

Title: Re: 392 transfer port size?
Post by: Rob112o on May 20, 2018, 04:10:01 PM

Yup, 392PA I have on 8 pumps gets 571FPS with the JSB 25.39 for 18.39 FPE.