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JeffNS · New Member

Before I jabber on allow me to introduce myself. I'm a 48yr old airgun enthusiast in Nova Scotia. I've owned scores of airguns during my lifetime and have recently moved to a rural area which allows frequent target shooting and occasional pest control without having to worry about proximity of neighbors.

Now...this subject has been discussed...possibly to death but I wanted to resurrect the topic for those looking for CURRENT information as there is lots of information on this and other forums which while current when posted is no longer applicable.

Please don't turn this discussion into one of the "do you have your Pal" or "it's illegal to mod an airgun to exceed 500fps in Canada without a Pal". I know, I know, I know. The purpose of my writing is simply the exchange of information. What you do in the privacy of your own home is your business.

As many are already aware, the Phantom 500 & Benjamin Classic .22 are based on the same power plant as the Phantom 800/1000 but have been "de-tuned" to meet Canadian regulations. Originally, Crosman had de-tuned these platforms by using a longer piston which reduced the swept volume of air. Then for reason's unknown to me they then opted to use the same shorter piston as was used in the Phantom 800/1000 but introduced a vent hole in the top center of the piston to regulate pressure and decrease velocity to allowable (Non-Pal) levels.

Some individuals were able to increase the velocity of their Phantom 500's and/or Classic .22 detuned rifles by filling the vent hole on the shorter piston (if a vented piston was Crosman's method of detuning) or by simply swapping the longer piston with the shorter non-vented piston from a Phantom 800/1000.

Well...for those who are not aware...at some point post 2011...Classic .22 rifles and perhaps Phantom 500's already employ the shorter non-vented piston which means they must now be utilizing a weaker mainspring in order to reduce velocity.

So...why do I bother to point this out?? Well, I opted to replace the piston in my Classic .22 which had no vent hole and had incorrectly assumed that it MUST be the longer piston so went ahead and bought a piston for the Phantom 1000/800 platform. It is exactly the same piston in every respect. For those reading older posts on this subject DO NOT...I repeat DO NOT bother with piston replacement unless you are absolutely sure your rifle doesn't already have the shorter piston installed already.

If your Phantom 500 or Classic .22 already have the shorter non vented piston installed then it is the mainspring that must be replaced in order to increase velocity. If your rifle has the longer piston then you can achieve velocity gains by installing the shorter non vented piston. If your rifle had the shorter vented piston you can either plug the vent hole or install non vented shorter piston.

Cheers

Robw · Veteran Member

Interesting. Do you find the detuned, lower powered version to be more accurate than the standard version?

Oh, and welcome to the forum.

Rob.

JeffNS · New Member

Accuracy ... if you're referring to the ability of a rifle to maintain consistent groupings ... will be unchanged given the ~450fps (detuned) vs ~720fps (full power) velocities. No issues with supersonic instability. However ... accuracy is sometimes and quite mistakenly interpreted as flat trajectory. This is when the full power version would prevail by reducing the rather large ballistic arc which exists with the detuned rifle. That being said, knowing your trajectory allows you to compensate as required at any given range but the higher velocity/flatter trajectory means the amount of compensation will be less.

I have not yet modded my detuned rifle but know in advance what gains can & will be realistically achieved.

Oh...just installed gtx gen ii trigger...definitely increases shooting enjoyment.

JeffNS · New Member

Accuracy ... if you're referring to the ability of a rifle to maintain consistent groupings ... will be unchanged given the ~450fps (detuned) vs ~720fps (full power) velocities. No issues with supersonic instability. However ... accuracy is sometimes and quite mistakenly interpreted as flat trajectory. This is when the full power version would prevail by reducing the rather large ballistic arc which exists with the detuned rifle. That being said, knowing your trajectory allows you to compensate as required at any given range but the higher velocity/flatter trajectory means the amount of compensation will be less.

I have not yet modded my detuned rifle but know in advance what gains can & will be realistically achieved.

Oh...just installed gtx gen ii trigger...definitely increases shooting enjoyment.