Canadian Airgun Forum

Alright, so i've been reading around the forum threads a bit, and i've stumbled upon some modding which involves cutting the piston in order to shorten it.

now, i've got a picture of a piston right here, could someone enlighten me as to where the piston is to be cut? the only possible method i see is to cut a piece of it in the middle and then put it back together, but then the piston loses strength and may even deform during the putting back together stage



Anyway, i'm just curious as to how this is done.

You'll need a Oxy-Acet set of torches even those cheapies for like under $80.cxnd and make sure you use a Mitre Box for a clean straight cut, The clamp straight and Braze it together properly straight. Exactly straight by means you should be able to figurfe out yourself. But no mote then 1" ands no more. Just Braze the Sear Slot back into place...Using an V Block would help alot... Braze as lot of holding poower more then you could imagine really alot like 85-PPSInch...

KM...

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We will never be the Man we once were, but what we will Become...

You want to shorten the piston to......???

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Doc

Aim Small. Miss Small.

I thought this was concerning a PAL rated AG...

Mike...

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We will never be the Man we once were, but what we will Become...

You don't want to chop your piston. The velocity will require it to be registered.

Cheers,
Todd

What model are you talking about here?

Crosman Phantom ... 495fps. He has a Phantom and has been asking how to improve it.

Cheers,
Todd

Like i mentioned, I read about it on the forum and i was wondering how this would be done without loosing any of the precision involved. By no means can I do all that work myself, and by no means am i interested in raising the muzzle velocity of the rifle since i would have to register it.

It was simple curiosity! Thank you Mike for your insight

Hi TCooper,

I understand what your saying here. But if the AG in question is already a PAL AG then the velocity wouldn't matter at all. Because it's already registered. You basically can do whatever you want to this AG thats a pal rated ag thats reg. ie: Use of a shorter spring for instance, as alot of the newer AG's of today are way over powered IMO, and cause way to much slam on the piston/seal also IMO

KM...

EDIT: No problem, but that information was from an article I was reading and it showed it being done with pic's. I just found it interesting. I was going to buy the Hatsan #125 but inturn found out they use the longer type of pistons in them which is Hatsans downfall in there AirGuns IMO. I've even asked them at Hatsan in Turkey why they don't correct this problem with no good answer in there H-Velocity AG's. They think that an AG with the Recoil of a 12g is kool I have no idea. Glad to help

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If the post that you are alluding to is in the thread about the antique Webley airpistol, perhaps I can help you understand what the poster's intent was.

With the Webley Senior, the piston is a one piece affair. There is no seal on the end of the piston, but rather, it uses a phosphor bronze piston ring, fitted into a groove, just slightly back from the front of the piston. What the poster describes, was to machine away some of the material from the front face of the piston, in an effort to increase the swept volume of air compressed by the piston upon firing. IMO, not a recommended modification, but other's opinions may vary - lol.

The above modification would not be applicable to the piston in your gun - at least not without re-engineering, and extensive machine work.

If you want to shorten a Phantom 500 piston- get a picture of one so you can visualize it better. The piston that is posted above is not going to give you the idea. If you compare that picture to one of a Phantom piston- the difference, and what you would need to do if you wanted to turn the Phantom into a PAL-rated gun becomes quite obvious.

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Please note: I do not conduct business through Private Messages (PM's) in online forums. Please do not send a 'PM" with a business-related question.

I think he misunderstood what I was saying here totally...


KM...

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We will never be the Man we once were, but what we will Become...

Never do it with Spring air rifles unless you are Stateside, and thus not locked down with restrictions.
In England we get 6ftlbs for pistols and 12ftlbs for Air rifles.
Removing any mass from the front of pistons will result in illegal velocites on anything bigger than a BSA Meteor.

The only pistol that you might get to go illegal in this way, would be a P5 or old BSA Scorpion....or something with a 7 inch stroke (which i may have overlooked.)

You would also need plenty of experience in the operation of a lathe, using high carbide tip tools.
Pistons are usually hardened to about 60 Rockwell to prevent sears or faces wearing but a carbide will cut it like butter if your speeds/feeds are set up correctly.

You may be better knocking out that front piston guide in Nylon, for improved smoothness, and slight vel increase, or using a slip ring below the spring.
Limited improvements only......piston guns are about swept volumes!

PM if you need anymore help.
More than One dude on here gave me a right slating over another topic for my past activiites such as this.

The main moan suggested that such work to my Webley Pistols could damage them.
This is a reasonable argument for the inexperienced (you need to know how much and how little)

The other argument centred around "people like me being partly responsible for increased anti gun lobbey activiites.
Given that no Webley will ever get beyond 5ftlbs (no matter what we do due to the small volume) HOFFMAN Weirauch might be more to blame.
They have been hitting about 5.7ftlbs with their HW45 for years.
One certain pellet in this gun will take this piece over in its standard form!

i sugest if you are thinking of doing this , that you try puting a plug behind the spring and see how much spair room you have to cut out of it ,
if you cut to much it may bottom out and then you have 0 f/s gun .
i know very little about this gun but , i do know that cutting it apart and welding it backtogether is not a good thing .