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Tuning Benjamin Cayden Hammer Spring

I have a question regarding the hammer spring mod that I am reading so much about for my Cayden. Let me first say that I am apprehensive about opening up any PCP, simply because I don't know what I'm looking at. I'm pretty mechanically inclined, but not familiar with the construction/internals of these. It sounds like something I can only BENEFIT from, which leads me to my next question. What is the trade-off? If this is so beneficial, then why wouldn't Benjamin have just installed shorter springs from the get-go ? Why are these so oversprung? Any pointers/advice is appreciated. Sounds like I will first have to empty the tank, correct ?? I really need a PCP - 101 course !! HAHAHA. Thanks for your patience with newbies to PCP world.
 
Man they are super simple, nothing to be worried about. Just take the stock off, there’s a threaded plug in the back with a flat blade slot. That’s your hammer spring adjuster, remove it and your hammer spring falls out. No need to degas the gun.

Other guys on here will give you the why they do and don’t do this or that, above my paygrade! Once you get it apart it will become easier to understand what’s going on. 


Beau

Edit: Disclaimer I don’t have any of the Benjamin guns made by Kral. I have the Krals though and believe they are pretty much the same, atleast dealing with removing the hammer spring.
 
Well, first off, Benjamin didn't build the Craftsman Series of air rifles, they are made in Turkey. Most folks believe they are made by Krale. I would suspect the springs are sourced from other Krale models and the same spring is probably used in the .25/.22 Kratos, .22 Cayden and .177/.22 Akela. My Cayden did not need the spring shortened and shoots a shot string that's as flat or flatter than some of regulated air guns. I did have to clip about a ½" off the spring in my .177 Akela because it was shooting way too hot and the shot string was a steady decline!

Shortening the hammer spring is pretty simple and doesn't require you degas the airgun. You will need to remove the stock (one screw) then remove the plug that retains the spring. It's been a while since I did it, but I believe it will be quite intuitive once the stock is removed and you can see the end of the airgun. Once the retaining plug is removed, the spring should slide right out. All you need to do then is clip it, re-insert it and reassemble the airgun. Should be about a 15 minute job! I'd also back the hammer spring adjuster all the way out and test it before you modify the spring, just in case it was adjusted too much from the factory!
 
Yes, which is why I suggested turning the hammer spring adjuster all the way out (but not to far that the stock won't go back on) and then see where you are before clipping the spring. You may not need to. On my Akela, it was just shooting too hot, well above 1000 fps with 10 grain pellets, so there was a lot of wasted air and accuracy was not that good. Clipping the spring brought the velocity down to around 925 fps and the groups tightened accordingly. Shot count also went up because it wasn't wasting as much air. But, as I stated before, that was on the .177 Akela, my Cayden is shooting 16 grain pellets at just under 950 fps, with a deviation of around 2 fps per magazine and stacks the AA 16 and 18 grain pellets into tight little clover leafs! If you are going to attempt to make any adjustments, I recommend using a chronograph so you know what your starting point is and then shoot it till you see the groups improve, when adjust to that velocity.
 
I'm also running just under 950 with 16 gr pellets at 3/4 on the power adjuster. I'm thinking maybe I should leave well enough alone now, since I still have a little more adjustment left for heavier pellets or slugs. It's really intriguing reading all the various comments on this new area for me. Cayden is REALLY grouping well at current settings.
 
I'm also running just under 950 with 16 gr pellets at 3/4 on the power adjuster. I'm thinking maybe I should leave well enough alone now, since I still have a little more adjustment left for heavier pellets or slugs. It's really intriguing reading all the various comments on this new area for me. Cayden is REALLY grouping well at current settings.

Sounds like yours is good to go! Mine is shooting the 16’s at just under 950 fps with the adjuster full open!
also, if you are concerned about the warranty, you can always contact Crosman and order another spring, that’s what I did for the Akela. They are only about $7 each, then you can put it back to stock if needed. 
 
I've been reading posts about the "cut spring advantage" for some time and I'm still on the fence about doing this. My Cayden shoots very much the same velocities as many others with factory adjusted rifles have posted and also very much as accurate with the 18-16-14gr ammo.... using only the power adjustment. NOW, one thing I've not tested - counted, was the number of shots I get from a fill down to where I decide to re-fill.... hasn't concerned me. WHAT I do wonder about is the sound I hear of the shot cycle. The rifle is moderated and I've never stood out front and listened while someone else pulls the trigger but I'm fairly certain the moderator is doing what it's supposed to do. The sound I hear at the receiver (action noise) is louder than I would expect it to be... in comparison to my other pcp rifles. So THIS is what makes me curious as to the rifle possibly being over-sprung and does the modifying (cutting) or adjusting the tension make a difference in quieting the shot cycle noise? Thanks to all that can address this.
 
I've been reading posts about the "cut spring advantage" for some time and I'm still on the fence about doing this. My Cayden shoots very much the same velocities as many others with factory adjusted rifles have posted and also very much as accurate with the 18-16-14gr ammo.... using only the power adjustment. NOW, one thing I've not tested - counted, was the number of shots I get from a fill down to where I decide to re-fill.... hasn't concerned me. WHAT I do wonder about is the sound I hear of the shot cycle. The rifle is moderated and I've never stood out front and listened while someone else pulls the trigger but I'm fairly certain the moderator is doing what it's supposed to do. The sound I hear at the receiver (action noise) is louder than I would expect it to be... in comparison to my other pcp rifles. So THIS is what makes me curious as to the rifle possibly being over-sprung and does the modifying (cutting) or adjusting the tension make a difference in quieting the shot cycle noise? Thanks to all that can address this.

You may very well have a barrel outer diameter o-ring that was nicked on assembly and is leaking a little when you shoot each pellet. That would account for the louder than anticipated sound you are having. I had this issue with my Kratos and had to replace both barrel o.d. O rings. The hole the barrel slides into inside the breech on the craftsman series has pretty sharp edges and it’s a really snug fit. You could also have a leaking o ring on the power adjuster which would give more noise. 

I’m not sure what moderator you are using but the Sumo from donnyfl takes away all shot noise from my Cayden, and there is no ping from the air tube which makes each shot pretty dang quiet even from the shooters perspective. 
 
pnwairgunner... Your response is appreciated... but, if that o-ring was nicked and allowing air to escape, would that not sound like an air escape - puff? and would it also allow a tissue to blow / move when draped across the breech / barrel end? that doesn't happen in my test firing. I hear a metal to metal "slap" upon firing. 

I pulled the stock, the hammer spring screw was loose - floating in its' place... not snug against anything, I screwed it in about a half turn 'til it touched, took another shot and it seemed to be a little less of a slap... could it be the screw / spring is not tight enough? allowing the slap - noise?

Suppose I'll need to experiment with tightening - loosening and firing through the chrony. My apologies to erock for somewhat hijacking his post.