This is the newest version of the MAGNUM ADJUSTER for 13XX made of 360 brass and 6061-T6 aluminum. It has a locking collar to maintain your setting, the collar can also be mounted with threadlocker to function as a knob instead. The striker spring can be removed by backing the guide-screw all the way out. It's compatible with all the hammer-springs we have listed. It fits 1377C, 1322C, PC77, P1377, P1322, 2289G Backpacker and 1300KT models.

 For maximum power, set spring tension to the minimum needed for the power level to peak. There's a valve-stem rebound effect that can cause power loss if too much spring tension is used.

 For the best accuracy, use the least amount of spring tension needed for the valve to empty fully. This lightens trigger-pull, produces tighter groups and reduces wear on trigger-group, valve and hammer components.

 The original Crosman screws are a poor fit and hit the threads on the adjuster guide-screw. Alloy-steel socket screws and a spacer washer are included. The washer is needed for the longer 11/16" screw, otherwise it may hit the threads on the guide-screw. Do not add a washer to the 1/4" screw, it's a perfect fit. Both screws require a 3/32 hex wrench which is not included. The small diameter of this adjuster leaves room for about two full threads of mounting-screw engagement. This is more than sufficient due to the high strength of the brass alloy. The screws should be snugged down firmly but not heavily-torqued. A small amount of medium-strength threadlocker can be used on the first few threads of the screws to keep them from loosening but still be removable. We haven't had any issues with damaged threads and we've sold thousands of these adjusters since 2009. This info is included only as a precaution for those who tend to over-tighten things to an extreme.


1) Make sure the gun is unloaded, uncocked and empty of pressure.  Remove the rear trigger frame and rear breech screws. Remove the tube plug which is where the adjuster will mount. It usually falls or lightly ejects out if you don't hold it while removing the screws. Install the threaded tube plug that’s part of the power adjuster, leave the guide-screw and locking collar off until the tube plug is screwed in place. Use the mounting screws that come with the adjuster, the factory screws are too long and will damage the adjustment screw. The longer 11/16" screw with one spacer washer is for the rear of the breech, the shorter screw (no washer) is for the rear of the trigger frame. Place the hammer spring on the guide-screw, make sure the spring goes into the back of the hammer as you thread the guide-screw into the tube plug. If you turn the adjuster knob too far forward the hammer will not pull back far enough to catch on the sear. Adjust to full spring-compression with the gun cocked, stop when you feel the spring is fully compressed, do not force it further. Back the adjuster out two full turns, this is the strongest setting that works smoothly in most cases. Peak power is often at a lower setting due to the valve stem closing faster (rebounding) from too much hammer spring force. 

2) With a power adjuster, custom valve or stronger hammer spring it’s typical to have to cock the gun to get the valve to seal so it can be pressurized.

3) The more striker spring tension you have the harder it becomes to pull back the bolt. With a heavier spring, especially if using a power adjuster, the bolt will pull back easier with your finger hooked around the front of the handle close to the breech. If done in one quick motion the bolt will pull back smoothly. If done slow or holding the handle further away from the breech the bolt may tend to bind or work rough.