This is a custom Discovery-based rifle with a tuned 26" Maximus barrel. In the most recent testing it produced 1147 FPS, 41.78 FPE, with a 14.3 grain lead pellet. With 25.39 grain JSB Monsters it produced 928 FPS which is 48.56 FPE. At 10 meters it consistently produces 3/8" groups. I generally keep it adjusted a little below full-power to produce a well balanced shot string. This performance level is shown in the following chrony results.
Test results using 14.3 grain domed Premiers, starting pressure 3200 PSI:
1) 1086 FPS
This .25 caliber carbine is the gun I used to develop the VALVE TO TANK ADAPTER and the discontinued .25 CALIBER CONVERSION KIT. The goal with building it was to make it as powerful, compact and accurate as possible with a massive shot count. It has a 14.5" barrel, is 31 inches long and has a 50 cubic inch unregulated carbon fiber tank. Starting with 2600 PSI it shoots a 80 shot string that starts at around 730 FPS, peaks at 760 and finishes around 730. These numbers are produced with JSB 25.39 grain domed lead pellets.
This .357 caliber rifle is sidelever bolt action. It has a removable 5 round rotary magazine or can be loaded single shot. I tuned it for more power and to function smoother for improved accuracy. It shoots 81 grain JSB pellets at 1000+ FPS and 145 grain Benjamin Nosler bullets at 820+. In the most recent chrony test the first five shots through the chrony were 811, 822, 828, 819 and 808. All five shots were 210-220 FPE. I accomplished this level of performance with the mods described below and the original striker spring adjusted to full tension. The starting pressure was 3100-3200 PSI to balance the power curve.
The second photo shows all parts that were improved and is fallowed by close-ups of some of those parts. The last two show the starting PSI and how to adjust the power level. I set it to low power by backing out the striker spring adjuster until it is flush with the housing. For high-power I tighten the spring adjuster until it stops.
This is a brief explanation of the work I did to this gun. The plastic sleeve that restricted the transfer port was eliminated. The valve and barrel ports were enlarged to match the transfer port. Contact points and surfaces were polished to smooth the trigger and bolt action. The valve and striker springs were re-ground to square them for smoother valve, bolt and striker function. The sealing edge on the valve stem was rounded more to improve air flow. The front cap on the shroud was bored off-center so I enlarged the hole just enough to correct that. All of the o-rings were upgraded to 90D for improved durability.
FOR HAND PUMP USERS : Starting at around 3100 PSI a five shot string on full power leaves about 2300 PSI left. Using a Benjamin hand pump it takes about 90 pumps to get back to 3100. After one full-power shot it takes about 17 pumps, 3 full-power shots about 55 pumps. Adjusted to low power it takes about 35 pumps after 5 shots and about 55 pumps after 10 shots. With 145 grain a ten shot string on low power starts at 500 FPS and climbs consitently to 640. With 81 grain a 10 round string starts at 650 and climbs consistently to 790. Using a hand pump is relatively practical if you limit yourself to 10 low power or 3 high power shots before filling. These results were achieved using Benjamin Nosler 145 grain bullets and JSB 81.02 grain pellets. This gun gets very difficult to pump as the pressure nears 3000 PSI, filling from a tank may be necessary depending on how strong you are and how much shooting you plan to do.
MORE TO COME
This gallery displays some of the guns in my personal collection.
CLICK PHOTO TO ENLARGE
MAGNUM DESTROYER .22