de tuned air rifles
- Thread starter rusty51
- Start date
OkayShooter
CGN Ultra frequent flyer
- Location
- Nova Scotia
Varies..
Shorter weaker spring, relief hole in the piston, longer piston.
Shorter weaker spring, relief hole in the piston, longer piston.
The piston is longer and this makes the stroke shorter. The spring is a small part but if you compare parts from the web site on some, they have the same. You can google how to shorten the piston. I have done a few or order the shorter piston from the manufacturer. If it is nitro piston your are most likely sol because the more powerful piston will not fit from what I have read. I wanted to up the power on my nitro but was told the strong piston would not fit. On pump or co2 they have valves that release over pressure for pump or reduce the flow of gas threw smaller holes for co2. You can increase these but will sometimes need to use different seals to do it.
I tuned a few springers and co2 rifles. Not hard to figure out with some help from Google.
I tuned a few springers and co2 rifles. Not hard to figure out with some help from Google.
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OkayShooter
CGN Ultra frequent flyer
- Location
- Nova Scotia
Take a Crosman Phantom. Ive seen 3 methods to detune it..
A longer piston with a regular full power spring.
Shorter piston with a full power spring and a relief hole in the piston.
Shorter piston and weaker spring.
Take a Crosman 1377 Canada model has a .089 transfer port where US has a .121.
C02 normally have stronger valve springs, or lighter hammer springs, more restricting valves.
A longer piston with a regular full power spring.
Shorter piston with a full power spring and a relief hole in the piston.
Shorter piston and weaker spring.
Take a Crosman 1377 Canada model has a .089 transfer port where US has a .121.
C02 normally have stronger valve springs, or lighter hammer springs, more restricting valves.
I have not played with air rifles for years. I have the phantom and when I tuned it there was only a longer piston and although the spring was different it was chronoed to have little difference. I'm sure over the year crosman has used other methods due to price or manufacturer.
With the hammer spring and valve springs. Some rifles do not have stronger counter parts, so to tune, you used after market springs or valves or simply increase air flow by making larger holes, also the seals on some rifles had small holes due to thick walls, so you could replace them with thinner or better seals. The qb78 had no other counter part. So you would enlarge the valve holes. And reshape the brass on the valve to help with air flow. Also the seals are compressed at the factory, closing the holes. This could lead to big variations in stock rifle power and was easy to fix with better quality seals. I tuned a few crosman rifles and never saw any other method during that time. I would just order the piston from crosman. I would polish and lube all parts. I never got into the more powerful springs in the aftermarket. I got enough doing what I did for my uses. I got a nitro piston and thought the Stronger nitro piston would just fit into my trail and was told by crosman that the Pistons were not compatible.
I never messed with the valve or hammer spring but the crosman 2240 pistols were good for these mods and I never got one.
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Weihrauch air rifles use a shorter spring when detuned to under 500 fps.
