The newest fad for Autocockers is to set up your marker so that the bolt pinches half fed balls instead of chopping through them.  Unlike most of the other cocker fads that have existed, this one is rather useful.  Everyone has been in an awkward position where the paint isn’t feeding as reliably as we’d hope, and eventually, one ball won’t feed completely.  The goal of setting your marker up to pinch is to make the bolt stop on that ball instead of slice through it. 

The main principle behind pinching is lowering the force required to cock the marker (because the ram closes the breach with the same force it uses to cock).  The main pitfall is that everyone thinks they need to lower the psi used in cocking the marker.  This isn’t really the case.  The pressure running through the ram is only part of the equation.  The diameter of the ram piston is the other half of the equation.  A cocker with a pneumatic pressure of 25psi will operate with the same force as one with a pneumatic pressure of 100psi if they have ram pistons of the proper sizes.  Since most rams that are used in paintball are all close to the same size (in terms of piston diameter), an equal pneumatic pressure will result in close to the same force created by the ram.  However, this isn’t true for all rams, for example the ANS ram piston is smaller than most, and the Professional Paintball ram piston is larger than most.  The larger the diameter of the ram piston, the lower the pressure required to reach a given force.  The smaller the piston, the higher the pressure required to reach a given force.

When ever people try and answer the question of how to set a cocker up to pinch paint, the first thing they say is to buy over $100 in new parts.  To be completely honest, none of that is needed.  While it may make things easier, it isn’t required by any stretch of the imagination.   The only things that need to be changed (most likely) are the springs.  If you have an adjustable pneumatic regulator it makes things much easier, but again, isn’t needed (just strongly encouraged). 

The main thing that affects the force required to cock the marker is the tension of the mainspring.  The weight of the mainspring is the heaviest force that the ram is working against.  When you lighten the mainspring, the ram doesn’t need to work against as much force, so you can lower the pressure with which it operates.  Obviously, installing a lighter mainspring will reduce the velocity, so you will have to adjust other aspects of the marker to counteract the effects.  The options you have to change are the input pressure, the weight of the valve spring, the weight of the hammer, and the position of the velocity adjuster.  If you adjust the velocity adjuster you are undoing the effects of a lighter mainspring, so I wouldn’t do that.  That leaves adjusting the input pressure, weight of the valve spring, and weight of the hammer.  Many people will suggest purchasing a heavier hammer, but as I said earlier, it isn’t really needed (it is a rather easy solution however).  The quickest, and easiest option is to re-sweet spot your regulator.  If you can’t achieve proper velocity, you will need to install a lighter valve spring.  If you adjust the valve spring tension, make sure to keep it a bit heavier than the mainspring, and then you will need to sweet spot the regulator again.  If you are still having trouble reaching velocity, go ahead and purchase the heavy hammer, but be sure that your mainspring isn’t too light.  A green Mad Man (or equivalent) should be fine.

After you have made sure you get proper velocity, it is time to set the pneumatic regulator.  To do this, first, lower the pressure all the way.  The marker wont cycle properly now.  Hold down the trigger, and slowly turn up the pneumatic regulator (now you see why it is helpful to have an externally adjustable pneumatic regulator).  Once the bolt clears the breach, leave the pneumatic regulator at that setting.  Fire off a quick string to make sure the pneumatic regulator can keep up, if it cannot keep up, gently up the pressure a small bit more.  If it can, it is now time to test your progress.  Take a paintball, halfway feed it into the open breech and let go of the trigger.  With any luck, the bolt will stop on the ball, and you wont have to clean up a mess.  If you do have to clean up a mess, don’t worry, just start over and try a lighter mainspring.

Many people suggest doing all sorts of other crazy things like polishing this or that, but chances are that you wont see a big improvement.  You can polish the bolt (if it is metal), polish the upper tube, polish the internal chamber of the ram, and polish the hammer.  But it is doubtful that you will notice any performance change, and it is doubtful that that alone will make your marker pinch paint if it didn’t before you polished everything.  The mainspring is the key factor in keeping the cocking force low; all the other things are gravy.

In terms of difficulty, setting up your marker to pinch is on the low end of the scale.  The payoff is very large, and well worth the effort.  As with all modifications to your marker, just take your time and be patient.  You don’t need any special magic potions, or any new parts (other than springs).  Just follow the above steps and you will be good to go.