Reducing Power Of Benji Disco??

[greenairrow888]

I have read posts of increasing the power of the benji disco by adding a threaded nut that pushes down on the hammer spring therefore increasing the tension of it making it strike harder. Is there a way to lighten the spring either by cutting coils or using a lighter spring altogether, thereby reducing the power/FPS ? Can this be done safely?? Has anyone posted about this subject and if so any links? If not any opinions?? By the way i want to reduce the power down so that it might be more accurate as im looking at just target shooting thereby needing less power/ FPS. Somewhere around 550 FPS. It should be safer to shoot indoors also which is my intentions. Also more shots at lower fill pressure?? Thanks Guys.

[airgunandy]

Crosman's new Challenger 2009 PCP target gun is basically a Disco in a modified Challenger 2000 stock and a Marauder trigger. Crosman rates it at 530fps. Unfortunately, Crosman's website doesn't have an exploded parts diagram to let us see what they did to lower the velocity.
Lighter hammer spring would be a good start. Maybe a lighter hammer too.

[Jeff D]

I just put the regulator from AOA in mine (pm me if you want to discuss pros and cons). Since it's adjustable, I've been trying to dial it in just right. I've put over a thousand test shots over the chrony and changed hammer springs countless time. All that said, I can't tell you what will work for you but I can tell you that MY disco did not respond well to lighter hammer springs. The lighter I went, the more variation in FPS there was from shot to shot.

What I ended up with was a shorter (about 2.5 wraps of the coil cut off) stock spring and about the same (maybe a little more) FPS spread than a stock disco but at lower speeds and close to 100 shots per 2000psi fill. It's a .177 and tops out at around 760fps with CPL's (long climbing curve with a pretty quick drop off). Well within my goals for the gun. 

The reg would work better if i were not going for lower speeds. I found that turning it up and increasing the spring rate improved consistency very nicely but the sound level increased and the shot decreased noticeably.

If you are going to stick with spring tension adjustments do 2 things. 1- Get a spare stock spring so you can cut one down a little at a time and have replacement ready to go. 2- get a light spring to experiment with. You won't be cutting it down but you might want to encase the end and use a screw as a power adjuster.

Mine does not respond well to a really light hammer strike. But the next time I'm motivated, I will swap in a stock spring cut shorter than the one in there now and add a power adjuster.  The way mine is set I could get 115ish shots at 10m powers with a slightly lighter spring, or 50+ shots at 30y powers with a slightly stiffer than stock spring, all at reasonable FPS variations. My best string, although too fast and too short, was shot before the reg was installed so you might have much better result playing with the spring.

[greenairrow888]

Those are some really helpful tips. Now the stock spring has ends with tighter coils than the rest of the body, if i cut off some coils do i count those tight coil end springs or the rest of the body. If i just cut those tight end springs then it would not be much huh? Also will not having those tight end springs affect any performance of springs or is it just cosmetic?? Most importantly, will having less spring tension somehow make the gun less safe as in going off even when trigger is NOT pulled? Intuitively the action appears to be almost similar to a striker fired gun and the trigger holding the spring back after cocking until release and if this is the case, would a spring that is cut short be any less safe? After your mod if i am understanding correctly you say that the FPS spread is similar to stock spring? If so that is neat to know that performance is not affected and that a reduction of 150 to 200 feet per second increases number of shots by at least double showing how much energy input (more air volume) it takes to increase energy output (FPS)