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Gamo CFX upgrade to Gas Ram

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mercs View Drop Down
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    Posted: 27 Dec 2021 at 6:00pm
Rifle Gamo CFX under-lever before and after Review


Year of Manufacture 2010

Usage light <3000 pellets

Plinking and target shooting, a little heavy for walking about but very capable for pest control.

Rifle is very accurate at 20 – 30 yards and generally lighter than many other under-levers.

New NZ$520 used $300

Overhaul Reason

Upgrade to Gas Ram and undertake improvements of existing trigger.

Some loss of power was suspected.

Findings

Spring had deformed, most factory edges remained sharp and all seals and o-rings had original assembly damage attributable to this.

Parts

Sourced from Custom AirSeals Australia:

Rotary Breech Seals

Piston seal

Gas Ram Kit

Overhaul was by local Engineering Specialist.

1. Sharp edges removed and honed.

2. Trigger sear shaped with diamond files.

3. Metal parts treated with molybdenum disulphide grease.

4. Reassembled and tested.

Outcomes

Accuracy was retained while recovering or gaining more than 2 ft/lbs of energy.

Cocking effort is a little heavier at the end of travel but is easily achieved with one hand.

Trigger weight remains unchanged but release is cleaner and more predictable.

Power increase was from 12.2 ft/lbs to 14.7 ft/lbs.

Notes

Some english reviews have the power down at 10 – 11 ft/lbs for statutory reasons.

Gamo factory Specification is for 720 fps, 17 ft/lb using lead pellets which is rather optimistic.

Numerous internet recommendations to install GRT-III trigger from CharlieDaTuna.com.

I note there is now a GRT-4G to replace Gamo plastic triggers.

The removal of sharp edges and reduction in damage at assembly will likely mean this rifle will never require disassembly of the pressure components again.


Chronograph Results 

Gamo CFX .22SpringGas Ram
Pellet BrandWebleyWebley
Pellet typeVMXVMX
average614673
Grains14.6614.66
grams0.950.95
foot pounds12.2814.75
Joules16.6420

20 Yards Bench Rest
Webley VMX pellets 1.0 gramme
Conditions were overcast with gentle breeze
Gamo rifle 140mm target card analysed with Target Scan App
Mean Radius of 1.9mm  and Diameter 4.6mm


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Billbobnz View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Billbobnz Quote  Post ReplyReply Direct Link To This Post Posted: 27 Dec 2021 at 8:44pm
That is awesome. I missed out on a cfx a few months ago. I'll put it on my to buy list.
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dvlnme View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote dvlnme Quote  Post ReplyReply Direct Link To This Post Posted: 28 Dec 2021 at 8:11am
that was worth doing mate,drop round see me will show you how to sort that trigger out to be just as good as GTR trigger,you can try the trigger out on my shadow and will see the difference ,we can get yours just as good give me a call if you interested
 cheers mike
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