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Author Topic: Gamo G Challenger  (Read 2628 times)

Offline Novagun

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Re: Gamo G Challenger
« Reply #15 on: September 26, 2016, 04:24:26 PM »
Yes I agree with you $750 is too much for the rifle. At that money one would do well to look at Ron Youngs' catalogue before buying. Those Challengers when they first came out were about $1200 if I remember correctly. They have been about for a while. My barrel date is 2014. I don't think they moved from the warehouse for a long time.

Your note piqued my interest and I looked up the Gun City site. No information on the challenger or the CFX but the spring version of the CFR with standard Gamo trigger and a Gun City scope ( that will be a goody) was priced at $699.00 reduced from $737. Way too dear.
However it must be an interesting rifle. The advertising states.
" Adjustable chin strap"
"CFR exquisite innovation in fixed barrel"
"Rifle in fixed spout"
'Place any shape of pellet or dart , close the barrel" 

'
« Last Edit: September 26, 2016, 05:19:39 PM by Novagun »

Offline Novagun

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Re: Gamo G Challenger
« Reply #16 on: October 13, 2016, 09:15:50 PM »
Challenger update.
Well the Challenger shoots very smoothly and is not too bad out to 10 – 12 metres. At 25 metres I found it disappointing. However it knocked over Field targets at 30 to 35 metres but 50 metres was too far. The sticking point was the poor groups at 25.

I found that the only pellets that engaged the rifling on a push through were H&N Field Target Trophy. AirArms (JSB) at 4.52 mms left no rifling mark at all and neither did JSB Exacts at 4.53 mms. From that I conclude that pellet sizes are nominal only.

A while ago I was given a CFX compression tube and barrel dated 2008. A good year I hope. It had to be tried but the SAT trigger set up and the IGT ram does not fit the CFX configuration and the piston sear would not engage the piston on cocking. I needed to shorten the distance the trigger assembly stuck out from the compression tube. That meant cutting the trigger group slot; re-drilling the locating holes in the trigger block and the compression tube and turning up two pins for an interference fit. Good fun if you like tutuing about…
On assembly I put an extra washer (2mms) behind the gas ram. A titch more preload there.

Reassembled it still shots smoothly but the power has gone up a bit. A bit more penetration into the radiata block. I think that comes from the pellet to barrel fit and not much from the extra preload. I will have to bump into the Combro again and measure the velocity. I guess pretty close to 12 ft lbs.
The downer is that the bluing on the barrel had a rust spot and slight pitting. Cleaning it off wore the bluing away. I can’t do anything about the slight pitting but covering it with a bit of black tape disguises it. The bore and rifling looks good and it so far it shoots well.

The IGT powered gun is very nice to shoot. Quiet and smooth.

Offline Novagun

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Re: Gamo G Challenger
« Reply #17 on: November 02, 2016, 09:07:38 PM »
Gamo Challenger. The next update.

Well the Gamo Challenger project marches on. I have played with muzzle weights and airstrippers and tried hard to convince myself that it was all pointing to improvement. The decider came last Sunday on the WAG indoor range at 25 yards. Result – the realization that this rifle as it stands is a piece of junk. The only worthwhile improvement so far has been the substitution of the CFX barrel. That was worth doing.  The rifle did not shoot well at 25 yards;  still not bad at 10 metres but really disappointing at 25 yds.

So in my own way I compared what was different between my much butchered CFX and this Challenger that was initially advertised for sale a $1275.00. I jest not because I saw the printed advertisement today.
The difference is the barrel and in my never humble opinion that is a problem. I had been hanging onto the tit on the muzzle because the ½ inch NF thread that I worked onto the muzzle enabled me to swap muzzle appendages as often as I liked. Big mistake.

To explain, and some of this is surmise but it seems logical to me.
The barrel diameter of 16mms OD is turned down to 12.5 mms at some stage during the production of barrel. This turn down is the bit that accepts the plastic CF range muzzle break. There is a spline pressed into the turned down part to stop the muzzle break rotating on the muzzle. That would take some pressure to press in and to stop the thinned down muzzle from crushing there must be a mandrel put into the muzzle to accommodate the pressure. There are marks that could have been made inside the muzzle by the work of twisting out the mandrel. Marks not unlike those that a twist drill would make.

The end result is that the final 25 mms of the barrel has no rifling. A pellet can be dropped into the muzzle until it hits the rifling and then it stops. It can then be shaken back out. The clearance between pellet and the unrifled part is slim, say .5mms or there abouts. That clearance must be such that either the skirt could interfere or the still confined airflow past the pellet skirt could interfere with the clean exit of the pellet from the barrel.  Whatever was happening is not good. I could not see that actual crown of the barrel down the hole so who knows what that was like and I destroyed it.

My remedy was to put a cut off blade into the circular saw and  cut 30 mms off. A chamfer of the muzzle with a twist drill and a polish of the crown with the brass screw.

Result: today the rifle shot one ragged hole groups of 10 mms at 25 yards and it did it three times.
I think, I hope I have got it right this time.

 I am still very happy with the IGT system and the SAT trigger.
I should be disgruntled that I bought this rifle but I am not. It is, in my never humble opinion, a good rifle. I am still very pleased with it and the tuting to get it right adds to the fun but this is not a rifle for everyone.

Offline Pauly5

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Gamo G Challenger
« Reply #18 on: November 02, 2016, 11:24:20 PM »
That's great Hugh. How satisfying to get those results.
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Offline Novagun

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Re: Gamo G Challenger
« Reply #19 on: June 24, 2017, 10:09:21 AM »
Wet day yesterday so I made an adapter so that the Gamo piston will accept a 25mm Wiehrauch piston seal. There is no doubt that the seal is better than the Gamo version. The sound has changed to a POP noise. Just the same as my CFX .
The weirauch seals are better than my home made ones but much more expensive.
Next thing to consider is either a more powerful gas ram or converting to wire spring.
When firing the CFX then picking up the Challenger, there is no difference in the firing cycle. Of course the
Challenger is heavier but not as powerful.
Both are accurate  one as good as the other. Not surprising really because the Challenger is really a CFX and both with the same modifications.
« Last Edit: June 24, 2017, 10:49:54 AM by Novagun »

Offline Novagun

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Re: Gamo G Challenger
« Reply #20 on: June 05, 2018, 07:47:16 AM »
The Gamo Challenger marches on. Not the rifle I bought from Mr Gamo. All the Gamo underlevers are fundamentally the same. But the Hammer forged barrel in the Challenger makes it a do not buy rifle.
My Challenger has had a CFX action for a while. I have tried it with the modest Challenger gas ram and a more powerfull one out of a CFR IGT. Now it has a standard steel CFX spring. Actually it has the CFR  mechanism with a steel spring mounted in the wooden Challenger stock. The extra weight of the stock makes it steadier to shoot and the stock doesn't flex like the plastic one. The CFR is the one I have with the barrel shortened about 150 mms.

I like the short barrels and my Webley Tomohawk now looks like a long tom.