Crosman 1720T - Manual (Page 7)

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• The 1720T is designed to be tuned to work at various fill pressures from 2500 psi (172 bar) up to 3000 psi
(207 bar). This is done by adjustment of the hammer spring preload and hammer stroke length. In either
case the adjustment changes the amount of energy the hammer generates when striking the valve. Higher
fill pressures require more hammer energy while lower fill pressures require less hammer energy. Higher
fill pressures will typically yield more usable shots from a given charge. It is advised to always record your
settings when tuning your airgun.
• The 1720T can be adjusted to achieve various velocities using the same procedures described herein.
This would mainly be done to compensate for heavier pellets IE 10.5 grain vs. 7.9 grain.
A. Hammer Spring Preload Adjuster
The hammer spring preload adjuster may be accessed through the rear plug on
the reservoir tube with a 3/16” Allen wrench as shown in figure 11. To increase
hammer energy turn the preload adjuster clockwise up to 7 revolutions. This
would be the case when starting from all the way back counterclockwise.
NOTE: More revolutions will simply cause the adjuster to spin but will not yield any
higher force. Increasing the preload will be required to facilitate use of higher fill
pressure.
To lessen hammer energy turn the adjuster counterclockwise. It is advised to
always record your settings when tuning your airgun.
B. Stroke Adjustment
The striker can be accessed through the hammer spring preload adjuster using a
1/8” Allen wrench (fig 12). Turning the striker clockwise will shorten the hammer
stroke and turning counter clockwise will lengthen the stroke. A long stroke length
will yield higher hammer energy while a short stroke length will yield lower hammer
energy. The striker can be adjusted inward by up to 12 revolutions though this
many turns would never be necessary.
• A starting point for low fill pressures would start with a low hammer spring
preload tension and a shorter hammer stroke.
• A starting point for higher fill pressures will require more hammer spring
preload tension and a longer hammer stroke. Refer to the chart below for sug-
gested combinations of these adjustments based on fill pressure.
Fill
Pressure
Hammer Spring Preload Hammer Stroke
Higher Increase, turn adjuster in (Clockwise) Increase. Turn Striker out (Counter Clockwise)
Lower
Decrease, turn Adjuster out (Counter
Clockwise)
Decrease. Turn Striker in (Clockwise)
Transfer Port Change:
As well as fine tuning adjustments possible with the Hammer pre-load and Striker settings, this pistol is in-
cluded with a smaller (.047” diameter) transfer port. Changing to the smaller diameter transfer port will lessen
the velocity achievable to approximately 550 fps max (depending on pellet weight) and increase the number of
shots to approximately 70 per fill. The lower velocity is intended for Silhouette shooting matches where higher
energies that may re-set or damage targets is undesirable. Be aware that changes to the velocity will affect
sight settings. The transfer Port change is meant as a one-time change to set the pistol permanently and not
a more “on the fly” type of change. Seek the aid of a Crosman Service station or qualified Gunsmith to change
the Transfer Port.
11. Reviewing Safety
• Never point the airgun at any person or at anything you do not intend to shoot.
• Always treat the airgun as though it is loaded and with the same respect you would a firearm.
• Always aim in a SAFE DIRECTION. Always keep the muzzle of the airgun pointed in a SAFE DIRECTION.
• Always keep the airgun on safe until you are ready to shoot.
• Always check to see if the airgun is “ON SAFE” (see section 2A) and unloaded when getting it from
another person or from storage.
• Always keep your finger off the trigger and out of the trigger guard until ready to shoot.
• You and others with you should always wear shooting glasses to protect your eyes.
• If your reading, or prescription, glasses are not safety glasses, make sure you wear shooting glasses over
your regular glasses.
• Use .177 caliber (4.5mm) pellets only in your airgun. NEVER reuse ammunition.
• Do not shoot at hard surfaces or at the surface of water. The pellet may bounce off or ricochet and hit
someone or something you had not intended to hit.
• Place the backstop in a location that will be safe should the backstop fail.
• Your backstop should be checked for wear before and after each use. All backstops are subject to wear
and will eventually fail. Replace your backstop if the surface is worn or damaged or if a ricochet occurs.
• Do not attempt to disassemble or tamper with your airgun. Use an Authorized Service Station. Using
unauthorized repair centers or modifying the function of your airgun in any way may be unsafe and will
void your warranty.
Fig. 12
Fig. 13