Fortitude Gen 2 Hammer Spring Adjustment
The Benjamin Fortitude Gen 2 hammer spring is adjustable. That’s one of the new features of the new model Fortitude, of course. So, HAM Publisher Stephen Archer couldn’t resist finding out if it makes sense to alter the factory setting.
Here’s what I found…
First, a reminder of the information Velocity Outdoors provides about Fortitude Gen 2 hammer preload.
|Preload||Preload Turns||Muzzle Velocity in .177 Cal||Muzzle Velocity in .22 Cal||Shot Count|
|No preload||0||Up to 650 FPS||Up to 600 FPS||Up to 200|
|Factory setting||4||Up to 850 FPS||Up to 750 FPS||Up to 90|
|Maximum||6||Up to 950 FPS||Up to 800 FPS||Up to 60|
The Benjamin Fortitude Gen 2 sample gun we have here at the HAM offices is in .22 caliber. To keep things “in house”, we tested it using 14.3 Grain Crosman Premier domed pellets.
This is how the Gen 2 Fortitude performed “out of the box” with the factory hammer spring adjustment.
Here we have a nicely-shaped curve of Muzzle Energy against the number of shots. There’s about 70 consistent shots before HPA pressure drops below the regulator setting. This is a pretty-well set-up regulated PCP air rifle!
Does it match the company’s claim of “up to 90 effective shots”? That’s for you to decide. What we can say is that Fortitude Gen 2 hammer spring preload at the factory setting gives about 70 CONSISTENT shots per fill of High Pressure Air for the gun tested by HAM.
Of course, most enthusiasts are going to set the Fortitude Gen 2 hammer preload to its maximum setting! More is good, right?
So that’s what I tried next. Here are some learnings…
Of course, you have the gun unloaded before starting this!
First, you’ll find that if you use a T handle Allen (hex) wrench to adjust the Fortitude gen 2 hammer preload, it’s far, far easier to take the action out of the stock first. Otherwise the stock severely limits rotation of the Allen wrench.
Second, if you decide to increase the hammer preload by more than the maximum figure given by the manufacturer, the gun will not fire! Yip, the sear will not release if you set too much hammer spring preload.
So carefully back-off the preload adjuster by about 1/4 turn counterclockwise then cock and dry fire – or try to. Keep backing-off and testing until the gun WILL dry fire. Now you have the maximum preload that can be set for your Fortitude Gen 2 hammer spring.
Here is the shot count curve for the gun tested by HAM with maximum hammer spring preload.
Hmmm, that looks pretty similar to the first curve, doesn’t it? So let’s put both sets of test data on the same chart and compare them.
Here we can compare the results from the Fortitude Gen 2 hammer spring preload setting in factory condition and at maximum preload.
Now we can see that increasing the preload gives minimal increase in Muzzle Velocity – maybe 20 FPS, on average, over the consistent shots. But it definitely gives a lower shot count with approximately 60 reasonably-consistent shots per fill.
The other limit for hammer preload is zero. So I cranked the Fortitude Gen 2 hammer spring adjuster back to the “full out” position. No hammer preload. Here’s the results…
Readers who have been taking-in HAM Technical Editor Bob Sterne’s series on PCP air rifles will not be at all surprised by this shot curve.
In his post “Using Hammer Strike To Control PCP Power“, Bob gives examples of how different hammer spring tension will alter the shot curve. Look at the bottom curve in his chart here…
As Bob said:
“Yes, tuning well below the plateau (10% or more) will give you wonderful efficiency, but will create two problems. The grey line above shows the primary one, where you will get a bump in velocity below the setpoint (like an unregulated bell-curve).
The other problem is that with the gun tuned for such a light hammer strike, it will be extremely sensitive to any inconsistency of the hammer strike, and the shot-to-shot variation tends to be high.”
That’s exactly what we have with the Benjamin Fortitude Gen 2 hammer preload set to zero. Thanks Bob!
So what is the result of this simple test? Personally, I’d leave the hammer preload exactly where it is! The factory has set the hammer spring preload very well in the gun I tested. Why mess with success?