Gamo CFX .17 Cheap Tune Up

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B4408
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Gamo CFX .17 Cheap Tune Up

Post by B4408 »

So I have had the CFX for about 5 years and with the boys have probably put 4-5 tins of pellets through it. now wears a Nikko 6-24 scope. I put a Charlie deTuna trigger in it early on which helped but the trigger was creepy, inconsistent, but not heavy. The main spring went clang, twang, clang on firing. Not knowing any better we accepted it.
Gamo CFX .17
Gamo CFX .17
DSC02652a.jpg (140.25 KiB) Viewed 583 times
Well after attending the Newcastle FT day a couple of months ago I came away with an appreciation of what a good AR can do. The PCPs were incredible to shoot but the biggest thing was how smooth a tuned springer can be and a good trigger is so important in any firearm.

So I read a lot on the web about tuning etc. and decided I didn't want to put $ into the rifle but wanted it better. Only way was to pull it a part and have a look, nothing to loose. Found sharp edges and rough stamped metal on all parts including the trigger sears. :(
I started by smoothing all the edges where the cocking leaver slide runs in the spring housing and any other edges with emery paper. The main spring clanging was easy to help by putting a plastic sleave inside the steel tube so there is no metal to metal contact, a piece of drink bottle did the job.
drink bottle spring liner
drink bottle spring liner
DSC02585a.jpg (81.43 KiB) Viewed 583 times
Then I looked at the trigger for a while to see how it worked. The sears are as they come stamped out of the sheet steel, well if you can call a rough, round, off angle edge a sear. Since there was lots of sear engagement I took to both with a file and then stone to get a clean sear edge on both for a definite let off point. The steel did not seem hard, it is a cheap AR. ( when I have it all apart again I will do some more honing, there is still room for improvement and plenty of steel).
trigger sears
trigger sears
DSC02587a.jpg (138.31 KiB) Viewed 583 times
The trigger has a sort of sear adjustment screw that isn't long enough to do anything useful. It runs through a plastic moulding that is pressed into the housing and wobbles about. I glued the plastic in solid and used a longer screw so I can adjust sear travel and reduced creep dramatically. You would not want to do this without shaping the sears first as I don't think you would be able to safely adjust it with the original sear shape.
sear adjustment screw
sear adjustment screw
DSC02588a.jpg (94.02 KiB) Viewed 583 times
Finished by lubing and greasing moving parts.
The result is that trigger is quite good, cocking action is smoother, less spring noise and with the JSB Exact 8.4gn pellets Matt put me onto it shoots very consistently.
35 m
35 m
DSC02595a.jpg (255.33 KiB) Viewed 583 times
So a cheap tune up can be done with a bit of thought and research.

Bruce
B4408
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Re: Gamo CFX .17 Cheap Tune Up

Post by B4408 »

The choice of pellets also made a big difference in group consistency. The JSB Exact 8.4gn are the best so far. Gamo CFX does have potential.
Here are a few sample groups.
JSB 5 shots
JSB Exact
JSB Exact
DSC02651a.jpg (90.54 KiB) Viewed 582 times
Checking trajectory to 35m with 25m zero, 3 shots, showed I needed a bit of right adjustment.
JSB
JSB
DSC02650a.jpg (89.23 KiB) Viewed 582 times
Other pellets at 20 m, 5 shot groups
pellet test
pellet test
DSC02649a.jpg (93.25 KiB) Viewed 582 times
Rear bag I made last weekend when it was raining.
rear bag
rear bag
DSC02656a.jpg (121.42 KiB) Viewed 582 times
Bruce
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grmkc
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Re: Gamo CFX .17 Cheap Tune Up

Post by grmkc »

Good job Bruce. The Interweb is a wonderful thing. :wink:
Ol 55
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Re: Gamo CFX .17 Cheap Tune Up

Post by Ol 55 »

Good job Bruce, you better bring it to Victors next Sunday.
Cheers
Gary
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stinkitup
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Re: Gamo CFX .17 Cheap Tune Up

Post by stinkitup »

Nice work Bruce...you sure got some skills :-)
B4408
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Re: Gamo CFX .17 Cheap Tune Up

Post by B4408 »

Gary, wont make Victors but let me know next time.
Stiinkitup, a little skill but lots of research, looking, thinking and having a go.
DIY doesn't save me money, I just spend it on something else. :lol:

Bruce
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Re: Gamo CFX .17 Cheap Tune Up

Post by mattw975 »

Nice shooting Bruce.

I have the BSA Superstar which is very closely related to the CFX & it is supremely accurate. The piston sleeve works well for killing twang.

A good old fettle works wonders on a springer. They benefit even further from a tight fitting top hat, spring guide & spring ends being polished.

If it fits in a specific gun, I have found Coles Blackcurrant cordial bottles make really good piston sleeves as they are nice & thick + hard wearing.

They also give a refreshing drink after a hard days tuning ;)
B4408
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Re: Gamo CFX .17 Cheap Tune Up

Post by B4408 »

mattw975 wrote:Nice shooting Bruce.

I have the BSA Superstar which is very closely related to the CFX & it is supremely accurate. The piston sleeve works well for killing twang.

A good old fettle works wonders on a springer. They benefit even further from a tight fitting top hat, spring guide & spring ends being polished.

If it fits in a specific gun, I have found Coles Blackcurrant cordial bottles make really good piston sleeves as they are nice & thick + hard wearing.

They also give a refreshing drink after a hard days tuning ;)
Matt, I think there is a bit more I can do around the spring area. Will shoot it for a while and and next time I service it or have rainy day, do some more mods.

Has anyone used seals from Custom Air Seals in Victoria?
http://www.customairseals.com/

Bruce
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grmkc
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Re: Gamo CFX .17 Cheap Tune Up

Post by grmkc »

Have been using seals from Laurie for a couple of years. There are around a dozen ARs that have been realeased back in the wild with his seals, including several of mine. All performing well to date. He's based on the west side of Melb. Makes a good seal. I like to support a local where I can.
B4408
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Re: Gamo CFX .17 Cheap Tune Up

Post by B4408 »

grmkc wrote:Have been using seals from Laurie for a couple of years. There are around a dozen ARs that have been realeased back in the wild with his seals, including several of mine. All performing well to date. He's based on the west side of Melb. Makes a good seal. I like to support a local where I can.
Thanks, may get a spare on hand ready for next service.

Bruce
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