Gamo Hunter Extreme - Questions

[Bone]

I recently got into the springers again. I'm still scratching my head as to why when I have PCP's that are awesome. 26 years ago I had a nice R1 that I kept for many years and never had a problem. I felt good about spending the money even though it was high It was a nice gun. I never took it apart so can't say about weather it had any major burr problems. Recently I bought one of those "dang" Gamo Hunter Extremes. I was sorry right off the bat. I took it out before taking it apart and the first shot with a 32 grain pellet and my chrony showed 710 fps. Cool I thought until the next round leisurely passing the chorny at 550 fps. What? I thought well she is new so shoot 50 pellets through it and check it again. Now it was under 500 fps and erratic.

So I called emailed Gamo and they are worthless. They just want you to play that game of sending the airgun back and forth and they still would not of fixed it right. If they are pushing them out the door like that then I need to fix it myself. They only sell parts to Firearm dealers. I told them that was stupid and I was told because of safety reasons. They said someone might hurt themselves removing the mainspring. I responded saying that information is safety and by choosing not to help us out is being irresponsible. I also said that using airguns are dangerous in general and the fact of people misusing them can be much more dangerous. Anyway I got nowhere and sense I'm a machinist I will make my own parts.

So after tearing into it I found the problems and all I got to say is that "Gamo not worthy". What a poorly made airgun. The seal was on e of the worst I have seen. Heavy duty burrs ripping the airgun apart. I have problems in other airguns as well so Gamo is not the only one screwing people over. I have a RWS 350 that was horrible. I tuned it and now it shoots great. My point is that we should not have to do this. Very poor workmanship!

So there's not much out there as far as help and that's why I have to ask some questions.

1. What material is best for the seal to made from?

2. How much interference is needed to maintain a good seal but at the same time not to much as to add drag to the action. In other words if the bore is 1.146 how big should be the outside diameter of the seal?

3. I noticed that the positive stop for the scope mount is already elongated and pushing the metal into the spring chamber. It is like a slot instead of a true hole. Do you think making it round and to the size of the scope mount pin would help?

4. The trigger is horrible and the sheet metal housing is so crooked that I had to straighten it back but there is still a mass of slop and so I will try and fix that as well. I have the trigger upgrade but the problem is much deeper. Any ideas here?

5. The sleeve (bull look alike) on the barrel is already bowing and then I seen that they have a plastic bottom butting up to the receiver. Anybody make a screw on muzzle brake for this?


6. Mainspring replacement? Is there one for it? If not I can get a spring made.

7. Rear spring guide was galled on the end of it. Looks like the spring has been smacking it. I'm thinking of making it a full ball on the end. Any suggestions?


I did not do enough homework on this airgun and should have before buying it. Now I will make do, figure it out and see what I can do with it.

Any help would be appreciated.

Thanks
Terry - Bone

PS - When I get done I will post pictures of what I found after 50 shots and new right out of the box.

[shadow]

The Gamo Extreme isn't too bad as far as finish but some can be on the bur side. I own a extreme myself and have tuned them for customers have a customers Extreme now and going through it. The first thing is that your pushing some heavy lead through it even for a magnum springer. Max that I would go would be upto .18g and mine loves the Predator pellet at .16g. airrifleheadquarters.com sells a piston seal and spring for the Extreme but for the seal you will need to machine a piston button screw attachment to hold it on. The seal is the Walter Talon mag seal and the spring is the Ultra Magnum spring. The GRT-III trigger is a true two stage trigger that will work great in the extreme. There is no direct aftermarket muzz brake and never seen one of the barrel shrouds bend. When I tune them I remove the rear guide and machine a delrin guide which is a proper fit and dampens spring vibration and buzz. I also machine a delrin guide for the upper portion of the tophat. On some magnum springers a second scope stop pin hole works but would need to be drilled into the compression tube. I put a raised rail on mine with two stop pin holes into the tube as well as tow stop pin holes for the scope mount itself, rock solid. When installing a new piston seal one should also do a hone/crosshatch on the compression area. This allow's the lube which can be had from airrifleheadquarters.com to lube the piston seal. My Extreme is my go to Magnum springer for small game and they do respond to tuning like a champ. Ed

[Bone]

Thank you for the information I really appreciate it.  It may be easier to make a screw then mess with different materials.  I was thinking of making a similar design but I was going to have the center of the seal .020 longer then the outside skirt so it would hit first and save the outside lip from getting pounded and deforming on the edge.

[shadow]

Actually you wouldn't want the center of the piston seal to stand proud. All it will do on impact is possibly damage the piston button and screw. I proper fitting seal has a parachute effect inside the compression tube along with conforming to the tube as it seat's/breaks in. If done right the piston seal will not be damaged and last for a long time. The most damage to a piston seal happens upon installation ether from the factory ot by the owner of the airgun. A small cut on the seal may not show up right away but will worsen as lube and heat find it. I just tuned a shooter that had the side of the seal melted from the top to the base and I could see the slice that started it all. I spent some time on my own extreme trying mod's until I found a combo that works. The biggest problem solver was designing a delrin guide to replace the metal one as well as lightening up the tophat. Heavy tophat's in any springer will create harsh recoil and some airguns like the Walter Talon Mag, Extremes etc. make their power with them but at the same time rattles the airgun apart.  Heck I'll give up a couple fps to get a solid firing cycle and dampened recoil. Power isn't everything if you can't control it and make it work for you and it's nice to shoot a magnum springer that doesn't want to jump out of your hands when shot. Any questions feel free to ask but take your time going through her and you'll be happy with the result's. Ed

[dwood5]

Bone,

My GAMO 440 is an older model but when I recently needed parts I found a cooperative FFL and ordered enough parts from GAMO [extra seals, springs, pins, etc.] to last a lifetime.

My rifle had some minor burrs which were easily removed. The trigger was total junk but when replaced with one of Tuna's triggers the 440 became one of my favorite rifles to shoot. It is not the most accurate and the trigger is not up to the quality of my RWS T06 or Weihrauch Rekord. But it is fun to shoot and somewhat of a challenge which makes it more enjoyable.

DON

[shadow]

If one can locate and obtain part's for Gamo's it's a plus part's for the Extrmes are even harder to come by. If tuning a springer and you perform a hone job on the compression area the stock piston seals will more then likely be to small and calling for a aftermarket seal. Ed

[Bone]

Gotta love forums for finding great information.  I wasn't going to  hone but have decided to do it.  The front piece where the barrel is attached needs to come off right?  Does it need to be heated to remove?  Is it loaded with lock tight?  I used the stock mount (the square welded piece to attach the stock with) in a vice to remove the other end.  I don't like the idea of putting that much pressure of the mount.  I fill the mount with a block of alum that is to size so I don't crush the stock mount but still worry that the welds may break loose.  I could make a special barrel clamp out of Delrin as hold the compression chamber.  Any help here is appreciated and thank you Ed and Don for you help!

Terry

[Bone]

Another question please.  Does the top hat have to be that undersize from the piston tube?  Will the cocking lever hit it?  Sorry for all the questions but you guys have been there and done that.  I also noticed that the piston tube slot varies 1/16 of a inch and it is bowed on top from them using a dull tool when punching the slot at the factory.  They should be putting inserts into the piston tube before punching the slot.  This would improve the quality of the slot when they punch it out.

Thanks much,
Terry

[shadow]

The barrel block pin that holds the barrel on just punch's out but to put it back you will need to tap it in some then hold the chisel blade back and tap the pin on through. My spring compresser is set up to accept the compression tube and barrel. The tophat, big weight in the piston cannot be longer. If you make it longer it will hit the spring guide when cocking and will not lock up. The only way to have a longer tophat is to shorten the guide in back and I would rather have a longer spring guide for better spring control. Ed

[Bone]

I was wanting the top hat to be closer in size to the I.D. of the piston housing.  Mine is .05 slop and tilts back and forth in the piston tube allowing the spring to bend.  So I was wondering just how much clearance does it really need.  To me it seems like I could make it closer like .010 clearance but not where it will not spin.  Then in the middle of the top hat I wanted to undercut the largest part of the OD and add a bunch of o-rings to absorb some vibration.  What do you think?
 

The barrel block pin that holds the barrel on just punch's out but to put it back you will need to tap it in some then hold the chisel blade back and tap the pin on through. My spring compresser is set up to accept the compression tube and barrel. The tophat, big weight in the piston cannot be longer. If you make it longer it will hit the spring guide when cocking and will not lock up. The only way to have a longer tophat is to shorten the guide in back and I would rather have a longer spring guide for better spring control. Ed

[gmupatriot2010]

I was wanting the top hat to be closer in size to the I.D. of the piston housing.  Mine is .05 slop and tilts back and forth in the piston tube allowing the spring to bend.  So I was wondering just how much clearance does it really need.  To me it seems like I could make it closer like .010 clearance but not where it will not spin.  Then in the middle of the top hat I wanted to undercut the largest part of the OD and add a bunch of o-rings to absorb some vibration.  What do you think?
 

The barrel block pin that holds the barrel on just punch's out but to put it back you will need to tap it in some then hold the chisel blade back and tap the pin on through. My spring compresser is set up to accept the compression tube and barrel. The tophat, big weight in the piston cannot be longer. If you make it longer it will hit the spring guide when cocking and will not lock up. The only way to have a longer tophat is to shorten the guide in back and I would rather have a longer spring guide for better spring control. Ed

If I understood you properly, you want the rear guide AND the top hat to fit the spring relatively snug. Like you noticed, if there is slop, the spring bends...and you will have spring twang and all kinda of erratic behavior

[shadow]

There's room for a slightly bigger tophat to take up the play inside the piston but you want a touch of play to let the tophat spin inside the piston. If the tophat cannot spin then the tork will really show itself during the firing cycle. Springers have a recoil back and also sideways and for me it's getting the insides setup to where it doesn't transfer all that rockin and rolling to the stock or at the most dampen it with a solid consistant firing cycle. Putting ribs in the tophat then adding O-rings probably won't last due to the tophat's spinning motion. I'm thinking the O-rings if your going with rubber will wear down quickly break away and begin their unwanted journey inside the action. Delrin rings would hold up for a very long time and also have a dampening ability. The tophat I machine is just the stock tophat with the shaft cut off then hit the drill press drill the base out. I spine a delrin shaft for the tophat base and install. If you take some weight out of the tophat it contributes to taming the harsh recoil and moves towards a magnum springer that doesn't wanna jump out of your hands when fired. Ed

[Bone]

Yes, but not snug enough where it wants to bind in any way.  The OD and ID dimensions are really sloppy and I can see evidence of galling on both ends of the stock parts where the spring is hitting them.  I'm also going to build the top hat with some sort of dampening device.  I'm thinking o-rings or may turn down the top hat to .374 dia and .730 long on the front so the post will be a little shorter then the washers going on and slide a .375 thick washer on then make a steel washer the same thickness that slides on the top hat and the overall length being retained.  Then the steel piece on the front of the top hat hits first transfering vibrations into the nylon.  I should be able to retain most of the weight keeping it on the stronger side.  Not sure about how well it will work but I thought I'd try.  I think a solid delrin one would do better as far as taming it down.  Maybe I should make both.     

Does anybody know the trick to getting the front receiver off before I just go for it. lol

[Bone]

I see.  Your taking the actual shaft that goes into the springs and changing them out with delrin.  A little weight loss but adding the OD back to the proper size I might get most of it back.  I agree completely.  It needs to be friendly and consistent.

Thanks again!

Oh, I think your right about the o-rings.  They would be pushing on that slot in the piston tube and when it would turn it would try to cut into it.   

There's room for a slightly bigger tophat to take up the play inside the piston but you want a touch of play to let the tophat spin inside the piston. If the tophat cannot spin then the tork will really show itself during the firing cycle. Springers have a recoil back and also sideways and for me it's getting the insides setup to where it doesn't transfer all that rockin and rolling to the stock or at the most dampen it with a solid consistant firing cycle. Putting ribs in the tophat then adding O-rings probably won't last due to the tophat's spinning motion. I'm thinking the O-rings if your going with rubber will wear down quickly break away and begin their unwanted journey inside the action. Delrin rings would hold up for a very long time and also have a dampening ability. The tophat I machine is just the stock tophat with the shaft cut off then hit the drill press drill the base out. I spine a delrin shaft for the tophat base and install. If you take some weight out of the tophat it contributes to taming the harsh recoil and moves towards a magnum springer that doesn't wanna jump out of your hands when fired. Ed

[SAADE]

Bone Said "26 years ago I had a nice R1 that I kept for many years and never had a problem. I felt good about spending the money even though it was high It was a nice gun. I never took it apart so can't say about weather it had any major burr problems. Recently I bought one of those dang Gamo Hunter Extremes. I was sorry right off the bat."

Oh, I doubt that the R1 had any "burrs" inside it, Weihrauch actually understands deburring and QC

[Bone]

I had a C1 back then as well.  Same way, excellent little airgun.

Oh, I doubt that the R1 had any "burrs" inside it, Weihrauch actually understands deburring and QC
[/quote]