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Author Topic: Gamo cfx.177 groups  (Read 6009 times)

Offline Greygloss

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Gamo cfx.177 groups
« on: February 16, 2014, 03:04:34 PM »
Hi all, just been having some pot shots in my back garden with this relatively new rifle. I could only get 13mtrs or so safely...and without annoying the neighbours too much ;-)
These are standing shots using some homemade shooting sticks to steady myself,  JSB Exact 8.44g pellets and a 3-9x40 tasco worldclass (non AO) scope.

I'm going to try somfe field shots soon at 50m and see how the groups open up....or even if I can hit the paper at that range! NB I do get the odd shot where the rifle has a sort of twisting recoil and that throws the odd flier .....any ideas folks?
« Last Edit: February 16, 2014, 03:09:16 PM by Greygloss »
I shoot like lightning.....never hittin the same place twice! ;-)

Patriot-Killer

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Re: Gamo cfx.177 groups
« Reply #1 on: February 16, 2014, 03:48:48 PM »
You'll get groups similar to that around 50m, bench rested. I know the CFX well,  and I cannot explain the twisting recoil unfortunately. All I can think is that it's still not settled / broken in yet. I would sample a 7-7.5 gn pellet, and see if you get the same twist. From my experience, that could be a sign that it wants slightly lighter pellets fed to it.

Offline Greygloss

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Re: Gamo cfx.177 groups
« Reply #2 on: February 16, 2014, 05:22:18 PM »
Thanks PK, I started off using gamo pro magnum 7.44g, but as I'm rabbit hunting, I thought a bit more weight would be good, and everyone seems to slag off the gamo pellets (although the tin of JSB's I had delivered were a lot poorer in quality in IMHO - although the supplier has sent me a new tin due to the amount of dinked pellets).
I am definitely thinking of changing my scope, a mil-dot and adjustable AO would be good as at 13mtrs my current scope's crosshairs almost cover the bulls eye. What do you use on your monster?
I shoot like lightning.....never hittin the same place twice! ;-)

Patriot-Killer

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Re: Gamo cfx.177 groups
« Reply #3 on: February 16, 2014, 07:02:00 PM »
No worries, Did you notice any twist with the Pro-Mags ?? I actually use them, and Expanders in my rifle. And as you say, many shooters are not fans of Gamo slugs. That is pretty much all I have used for over half my life, ever since my first ' full power ' air rifle. Both .177, and now .22.
I have tried many many others, and I have not for the life of me, found any performance deficit using Gamo slugs.
I will admit, some are not cast too well, with some over-cast burrs on the outer surface. But over the last few years specifically, I have found them very consistent / clean.
Try expanders, they ( in my rifle, at least ) do expand alot on impact and leave a much bigger exit hole in ply wood, than most other pellets. I do also like the stopping power of the Pro-Mags - but again, many haters. But that's fine, some guns like them, some don't. I can guarantee your quarry isn't going to laugh at your pellet selection, when they are being drilled-a-new-one with 15 /16 odd ft/lbs from your CFX
As for scope, I have a bullet-proof 4x40 AO Nikko Stirling MountMaster, secured with 16 bolts ( 4 in each ring clamping the scope, 4 more in each, onto the picatinny rail ).  Not a mil-dot, but I personally like clean crosshairs.
As for pellet weight, you will find that the fpe will remain pretty much the same with any weight pellet - fired from the same gun. As the grain weight goes up, the fps goes down, and vica versa. You may notice a slightly harder 'thunk' upon impact with heavier pellets - but they will not actually be delivering any more power to the target.
If you are getting over-penetration issues, the slower moving ( heavier ) pellet selection should fix that. That way all of the pellets energy will be delivered to the target. Through-and-through shots may seem awesome - but they aren't, you may as well be using a lower powered air rifle.

Edit : I suggets you do not use Gamo Raptors, or other light pellets under, say, 6.5gn. Or anything over 9gn weight. The sweet spot for springers is mid-weight. Anything outside these weights may damage your rifle !
« Last Edit: February 16, 2014, 07:07:41 PM by Patriot-Killer »

Offline Greygloss

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Re: Gamo cfx.177 groups
« Reply #4 on: February 16, 2014, 07:40:32 PM »
To be honest,  I don't recall getting the twist recoil when I was using the promagnums but It has only happened a couple of times, more so just recently. Just wondered if something was going wrong inside. I'm thinking of giving it a tune up, everyone says gamo over grease and I do get the odd smoking shot. I have probably put 1000 pellets through it now so it should be well "run in".

I haven't looked at the Nikki Stirling scopes, just the leapers and Hawke so far but I'll take a look.

Nb I switched to the JSBs as I was looking at the Chairgun software program showing flatter trajectory of the slightly heavier pellet, but of course I was assuming the velocity would remain the same. Perhaps I should borrow a chrono and see the difference.
I shoot like lightning.....never hittin the same place twice! ;-)

Patriot-Killer

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Re: Gamo cfx.177 groups
« Reply #5 on: February 16, 2014, 09:07:15 PM »
That would be a good idea, that way you can work out the Chairgun programme properly, knowing the velocity is key to using that programme.
I would also go back to my initial theory ( knowing it's well run in ) that it wants slugs under 8 or so grains.
The occasional twisting could be that the heavier JSB's you were using, were right on the borderline for what your gun prefers weight-wise. If there was an internal issue, that spring torque would happen every shot. As for the smoking, As long as there is no 'crack' when fired, that extra lube will burn away in time. Tuners do suggest a 'Gamo over-lube' cleanout, but that is really only of you want a spanking-new rifle to be run-in asap. After 1000 shots, In my opinion, there will be no point doing that - but that's just me. Most of that smoke will be crap burning out of your barrel. It can take alot more to get it all out, as you are also adding a lining of lead as you shoot. No harm in giving the bore a few runs through with a patch, or similar.

Offline Greygloss

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Re: Gamo cfx.177 groups
« Reply #6 on: February 16, 2014, 10:28:29 PM »
Thanks for the advice, maybe I'll leave well alone while it seems to be pretty accurate. I do have a GRT4 trigger on order which apparently makes it a much smoother rifle to shoot, so it will be interesting to see if it makes a difference. Cheers
I shoot like lightning.....never hittin the same place twice! ;-)

Patriot-Killer

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Re: Gamo cfx.177 groups
« Reply #7 on: February 17, 2014, 09:08:03 AM »
Thanks for the advice, maybe I'll leave well alone while it seems to be pretty accurate. I do have a GRT4 trigger on order which apparently makes it a much smoother rifle to shoot, so it will be interesting to see if it makes a difference. Cheers

All good  :D Anything else about that particular rifle you want to know feel free to ask. I would have to say I know more about that model than any other out there.
Did you know the front F/O sight slides out sideways ? I removed mine so I didn't snap it, they cost like $40 to replace. And in some conditions they are actually visible ( all be it blurry ) through the scope.
You will certainly notice a difference with the GRT trigger, a little more predictable , and smoother / lighter sear disengagement helps accuracy, as you are not moving the rifle as much when you fire.

Offline Greygloss

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Re: Gamo cfx.177 groups
« Reply #8 on: February 17, 2014, 10:20:44 PM »
Haha, you might regret offering that! All advice greatly received though as I'm still finding my feet with this rifle. I did try a 50mtr target tonight, groups were a bit like buckshot but I did manage 40mm groups, in my defense there was a brisk crosswind ;-)
I took your advice regarding a make of scope, just ordered a 4-12x42 nikko airking, read a few other reviews and everyone says you can't beat them for value....perhaps I should do one myself.
Popped a bunny straight between the ears at about 30mtrs from with me trusty pro-magnums...after I got fed up with the targets. As you say, it didn't laugh at my choice of pellet ;-)
« Last Edit: February 17, 2014, 10:34:36 PM by Greygloss »
I shoot like lightning.....never hittin the same place twice! ;-)

Offline Greygloss

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Re: Gamo cfx.177 groups
« Reply #9 on: February 18, 2014, 10:26:46 PM »
Just fitted my new shiny scope this afternoon and what a difference having an adjustable objective makes, just tried it out in the back garden, so no long distance shots yet but pleased with the result so far....that was 5 shots in the bullseye. (This target has .5 inch rings).
I shoot like lightning.....never hittin the same place twice! ;-)

Patriot-Killer

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Re: Gamo cfx.177 groups
« Reply #10 on: February 19, 2014, 12:25:35 PM »
Nice group - and no worries about the advice, finding a Gamo-nut is almost as hard as hitting a 50m target with Tommy Gun  ;D ::) So I'll be anyone's nut that asks a Gamo question !!

Offline Greygloss

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Re: Gamo cfx.177 groups
« Reply #11 on: February 19, 2014, 04:39:13 PM »
Thanks PK - good to know there's another nutcase out there who likes their gamo  :D
I'm still getting that twisting recoil though - its got worse since I put the new scope on it (which is heavier than the tasco, so maybe its a weight thing combined with where i'm supporting the rifle on the shooting sticks. It can be quite violent (relative to the usual recoil). I tried going back to the lighter promags but no difference. I moved to a benchrest hold under the stock and that was better (which got me the nice grouping. I'm just wondering if the spring is catching on something as it unwinds/decompresses giving the opposite torque. Hopefully my new trigger will turn up soon, so i'll have the perfect excuse to crack it open and have a look inside and tinker/polish...and break probably lol! Be good to get an answer to your thread about "whats the best lube to use" - might be handy soon.
I shoot like lightning.....never hittin the same place twice! ;-)

Patriot-Killer

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Re: Gamo cfx.177 groups
« Reply #12 on: February 19, 2014, 05:13:19 PM »
Thanks PK - good to know there's another nutcase out there who likes their gamo  :D
I'm still getting that twisting recoil though - its got worse since I put the new scope on it (which is heavier than the tasco, so maybe its a weight thing combined with where i'm supporting the rifle on the shooting sticks. It can be quite violent (relative to the usual recoil). I tried going back to the lighter promags but no difference. I moved to a benchrest hold under the stock and that was better (which got me the nice grouping. I'm just wondering if the spring is catching on something as it unwinds/decompresses giving the opposite torque. Hopefully my new trigger will turn up soon, so i'll have the perfect excuse to crack it open and have a look inside and tinker/polish...and break probably lol! Be good to get an answer to your thread about "whats the best lube to use" - might be handy soon.

Hmmmmmm - that spring torque thing is odd in the sense it's not consistent. However, I can explain why it is more pronounced with the scope on. It's more top-heavy now those Tasco's are light, any twist will naturally seem more-so, than without an optic up top.  And also too, looking through a magnified scope, any movement from the twist will give the same illusion - it'll seem like it's moving more - it's not. I think it's just that you have a twisty gun - that blows, but it can be tuned out.
I have never come across a twisty Gamo rifle - I've owned 6 myself, and shot almost all models. All I can suggest is get that trigger in, while she's in bits, have a look for broken coils on the mainspring in the cylinder, check for other damage too. I do hope that is not the case.
« Last Edit: February 19, 2014, 05:15:30 PM by Patriot-Killer »

Offline Greygloss

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Re: Gamo cfx.177 groups
« Reply #13 on: February 19, 2014, 09:51:04 PM »
I hear what you're saying about the greater magnification making it more obvious, and I would be happy with that if it had been occurring the moment I put the bigger scope on, but it was happening a few times before that and I think it's just getting worse. I couldn't resist stripping down the gun as the spring was sounding crunchy when it was compressed. I would appreciate your opinion on the state of the spring, no cracks or anything but it's got a pretty hefty bend in it, is that ok?
I shoot like lightning.....never hittin the same place twice! ;-)

Patriot-Killer

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Re: Gamo cfx.177 groups
« Reply #14 on: February 19, 2014, 10:25:17 PM »
I have to say, that about 100 different expletives come out, when I saw that spring - I didn't realise I could speak so much French  ;D ;D ;D ;D

It looks like it's well worn out. Extremely so. You say you got the gun new ?? I'd take it back to where you got it, and start your own French lesson to them.

That is not a new spring  :o

I would put it back together, make sure you don't damage the screws ( where the driver sits ) as you opening it up most likely will have voided the warranty. I suggest you get them to re-open it infront of you so they can't say "it's fine".

Man, that spring is in bad shape - excuse the pun.
« Last Edit: February 19, 2014, 10:28:47 PM by Patriot-Killer »