Trail nitro piston exchange

[jimdandy]

Hello everyone
I would like to swap out the nitro piston that is in the trail np xl .177 that I have. I was wondering if I got a smaller gas ram if it would calm it down some? I shoot exact monster diablos 13.4 gr to help calm it down.

[Robert 5mm]

The compression chamber the piston rides in is a diameter along with the piston and piston seal.
The gas ram just pushes on the piston and is not part of the diameter of the piston/chamber.

A spring piston can be de-tuned but the Nitro Piston gas-ram is another story - I do not think you can let gas out of the gas-ram on a Crosman.

[Roadworthy]

The answer to your question about a smaller gas spring (Nitro Piston) calming it down some is probably yes.  I believe the gas springs from the NP2 series are the same diameter but I do not know about the length.  The gas springs from the Nitro Piston series are a bit smaller in diameter but again, I do not know about length.  You may need to do a bit of experimentation, learning as you go.

[Robert 5mm]

If the gas-rams of the different Crosman/Benjamin models are the same dimensions - you should be able to switch them.

My NP2 piston is not the same model number as the NP XL piston nor the NP piston. ( My NP2 gas-ram does not have a valve ).

If the different model gas-rams are different lengths then the stroke of the piston is probably different. ( my earlier post was about the bore ).

Piston latch-up to trigger and stroke of the piston to end on compression chamber

Sounds like a project.

[ALWIII]

 Late to the party, but thought this might be useful. The NP in the Trail NP XL is unique. The overall length is 300 mm, the cylinder is 169 mm and the shaft is 131 mm. The diameter is 18 mm (same as the rest of them), but the length is a good 19 to 20+ mm longer. The shaft is also 20-30 mm longer than the others. To make a lower powered NP work you would have to shim it considerably, if that would even work.
  A new seal would tame the recoil and smooth things out considerably. I use this one, Pyramyd part # PY-A-4098 Of course, if the power is the problem the new seal will make it worse-it will pick up some power. If taming the recoil is the goal, that seal will help.
  As a side note, deburr the stamped slots in the air chamber before installing the new seal. The manufacturing process leaves sharp edges that cut the seal lip.

[ALWIII]

  Update-Air Magnum in Ukraine can make you a gas ram for the NP XL at any pressure you want. 

[ricksplace]

Crosman detunes its np rifles for the Canadian market. Crosman uses various methods of slowing them down. Here's an example:
I obtained a Crosman F4 Fire that was detuned at the factory to less than 500 fps. This was done by lengthening the piston to decrease the compression stroke, venting the face of the piston, and a very weak strut. The vent(s) in the face of the piston were filled with JB Weld. I swapped the nitro piston out and dropped in the nitro piston from a (Canadian detuned) F11 Crosman (22) and left the longer (170mm) piston in the Fire. The net effect is a short, snappy shot cycle that drives a 7.2gr wadcutter at 700fps with minimal recoil.
In your case, your rifle has the short (150mm) piston for the maximum length of compression stroke, and a full power np strut. I'm guessing my Fire would gain about 80-100 fps with the short piston. If you just swap out your full power np strut for the strut from the detuned F11 rifle, (I wish I could remember the part #) I'm guessing your rifle would shoot around 750-800fps with 8gr pellets. That should tame it right down.
I don't know if the aforementioned strut will fit your rifle, but there may be a detuned strut available from a (Canadian or UK) detuned model of your rifle.
(edit): If there is a detuned model of your rifle, there may be a longer piston used to decrease the length of the compression stroke. Installing the longer piston with your full power np strut would make for a snappy shot cycle and slow it down some.