Benjamin Trail NP XL 725 Tunes/mods ?

Jump to

Author Topic: Benjamin Trail NP XL 725 Tunes/mods ?  (Read 609 times)

Offline jrhunter

  • Sharp Shooter
  • ****
  • Posts: 274
  • Real Name: Sean
Benjamin Trail NP XL 725 Tunes/mods ?
« on: September 09, 2013, 08:27:38 PM »
My friend ask me if I know anything about a mod or tune that will increase the velocity and accuracy of his .25 caliber Benjamin Trail NP XL 725. I told him I would ask on here, so here I am asking ! ;D His gun averages 650 with 25.4 JSB Kings and gets .489 " CTC at 15 yards, .565" CTC at 18 yards, and .791" CTC at 20 yards. He was wondering if he could get an extra 45 fps ( 650 to 695 fps ) to get from 23.9 ft.lbs to 27.25 ft.lbs. He has a GRT-III on the way for his groups, but only thinks it will shave .080" off his groups ( exp. .489" to .409" ), and would like to get around .100" off his groups ( exp. .489" to .409" to .309" ), so is there any other mod to increase his guns accuracy down even more ? I told him to get a new breech seal and get some shims to increase his velocity numbers a little, would this work ? What other mods would increase the seal between the barrel locking to the gun ? His gun sometimes has problems getting shut and staying shut. What do the Brass Barrel Pivot washers form airguntoyz  do ? Would that help his problem with the barrel ? Where could he get a new barrel for his gun ? The ones that are in different calibers like the .22 and .177 ? He also wants to know if you can install a power adjuster on the gun, can you ? How ? He also wants to hunt, but since the velocities are so slow, I didn't know what to tell him. So could he hunt rabbits, squirrels, and pest birds at 50 yards or closer ( after the velocity increasing mod to get more energy ) ? Could he dispatch raccoons who get into his garage and into his garbage and recycling bin ? He also wants to know how to increase the swept air volume. Now when he wrote down the list I acted like I knew what he was talking about, but I don't. What is swept air volume ? Could you increase it ?
  • Columbus,Ohio
- Crosman 760 Pumpmaster .177
- Hatsan 1000S Striker Vortex Gas Piston .22

Offline Doug Wall

  • Barrel Cockers
  • **
  • Posts: 51
  • yes
Re: Benjamin Trail NP XL 725 Tunes/mods ?
« Reply #1 on: September 09, 2013, 08:55:25 PM »
You're pretty much stuck with what you've got. You would have to increase the piston stroke length, or increase the diameter of the piston to get more swept volume, neither of which is practical. You can't install a power adjuster. Even a more powerful gas ram would just make it harder to cock, and probably ruin the accuracy. A good cleaning of the cylinder and piston, and some proper moly grease might get you a few more fps, (maybe 5 or 10) but nowhere near 45. I doubt that his breach seal is leaking. You don't mention which pellets he's using. Lighter pellets will give numbers closer to the 725, but manufacturer reported velocities ar almost always on the high side. Instead of trying to reach out to 50 yds., concentrate on stalking skills to get closer. Your accuracy will be better, the target will appear larger for better aiming, your terminal velocity will be higher, and you'll have less pellet drop.
  • Hilton, NY

Offline jrhunter

  • Sharp Shooter
  • ****
  • Posts: 274
  • Real Name: Sean
Re: Benjamin Trail NP XL 725 Tunes/mods ?
« Reply #2 on: September 09, 2013, 08:59:56 PM »
You're pretty much stuck with what you've got. You would have to increase the piston stroke length, or increase the diameter of the piston to get more swept volume, neither of which is practical. You can't install a power adjuster. Even a more powerful gas ram would just make it harder to cock, and probably ruin the accuracy. A good cleaning of the cylinder and piston, and some proper moly grease might get you a few more fps, (maybe 5 or 10) but nowhere near 45. I doubt that his breach seal is leaking. You don't mention which pellets he's using. Lighter pellets will give numbers closer to the 725, but manufacturer reported velocities ar almost always on the high side. Instead of trying to reach out to 50 yds., concentrate on stalking skills to get closer. Your accuracy will be better, the target will appear larger for better aiming, your terminal velocity will be higher, and you'll have less pellet drop.


25.4 grain JSB Diablo Exact Kings
  • Columbus,Ohio
- Crosman 760 Pumpmaster .177
- Hatsan 1000S Striker Vortex Gas Piston .22

Offline OleTomCat

  • Tree Rats Beware.
  • Old Timers
  • *****
  • Posts: 5727
  • yes
    • GTA Web Map
  • Real Name: Al
Re: Benjamin Trail NP XL 725 Tunes/mods ?
« Reply #3 on: September 09, 2013, 10:31:35 PM »
Ok, lots of questions.....

Swept volume is the total amount of air that is moved by the piston to shoot the pellet, it is the area in the compression chamber between the seal at full cock and the pellet in the chamber and is pretty much fixed for each gun, some tinkering can be done but you really are pretty limited by the dimensions of the gun as manufactured...

The barrel bushings from Gene replace the plastic ones on either side of the barrel and help with side to side wobble on the barrel.

Cleaning and greasing the pivot joint and the chisel (the little thing that holds the barrel in the place when cocked) will help with lockup.

Barrels can be ordered from Crosman...

A stronger gas ram and tune may give you the best results for fps/fpe...

I have taken Racoons and Possum with a .177 in the 14fpe range, so I don't think he would have any problem with the .25 in 20fpe range....
  • Summerville, SC
Home Of Air Guns Inc.
Air Gun Tuning and Targets

Air Guns:
Sheridan Blue Streak, aka The Blue Demon Rebuilt Steroid Style By Mac1.
Gamo Silent Cat, tuned by Me, smooth as butter.
Crosman Storm, GRT-III trigger. Crosman N2 Ram. (For Sale)
Gamo Big Cat, GRT-IV Trigger, Custom installed N-Forcer Ram
Hatsan BT65: Big Nasty
FD PCP: ???

https://www.zeemaps.com/map?group=962067

GTA - The best place for discussion about Air Guns.