Gamo Hunter Extreme - Tune / Improvements?

[customfab]

I just purchased a Hunter Extreme .177 from Cabela's in the clearance center for $340.  I've done quite a bit of research on the gun and understand it has mixed reviews.  It is actually someone disappointing considering the retail price of over $500 but luckly my purchase price makes it somewhat less painful.  Kinda crazy that a $500 air rifle doesn't shoot very well out of the box.  I'm no competitor target shooter but do enjoy recreational target shooting on my back lot along with small game hunting.  I added a Leapers 4-16x50 AO scope and have since shot about 200 rounds of Baracuda Extra Heavy Match pellets.  I have yet to try other pellets but will soon try a few other brands for reference.  

This gun is frustrating to me.  I'm impressed with the power and abiliy to shoot heavier pellets.  The punch power is immense and certainly far superior to my RMS 34.  However, there is a rather large range of inconsistency and frankly I can shoot better with my RMS 34 at 40 yards with fixed sights!  I'll get groups within a 1-1.5" (thinking I'm almost there) and then randomly a few shots will stray several inches.  Very randomly.  This is my first Gamo, and I've already ordered a GTR-III trigger (OEM trigger is terrible compared to my tuned RMS 34).  

I'm very interested in performing a home tune on this gun to hopefull improve its accuracy & precision.  Is anyone familiar with tuning this gun?  Can you please provide some insight including parts or areas of focus which may make a difference?   I self-tuned my RMS 34 with great results but certainly wouldn't come close to calling myself a seasoned tuner, although I'm very talented with my hands & anything mechnical.    I can't seem to find any threads on this particular gun and improvements.  

[customfab]

I've read about all I can find & understand the bore of this powerplant is unique (no surpise).  I understand that aftermarket seals such as Maccari or Apex can be used if I special adaptor is machined.   Does anyone know where I might be able to purchase said adaptor?

Still love to hear about owner's or tuner's experience with this gun & improving the performance!!!  

[longislandhunter]

Hi Devin,,,

I have a GAMO 1250 (older version of the Extreme) in .22 that was made in England and I love the rifle.  Except for the GRT trigger my 1250 is still stock and she's extremely accurate.  The GRT trigger made a big difference in my rifles accuracy but the other accuracy factors are finding the right pellet and lots of practice with the rifle.  The 1250/Extreme is magnum springer and as such it will take you some time and practice to "get the feel" for shooting her accurately.  My rifle likes several pellets but right now I have her sighted in for Predators and she'll shoot dime sized groups in my 30 yards range all day if I do my part.  Get some different pellets and do some grouping tests.  Beeman FTS are worth a try, CPL's in the brown box, CPL Ultra Mags and perhaps CPHP's.  

AS for tuning,,,,, you will be very hard pressed to find parts for that beast.  I recently picked up a spare spring just so I"d have it in case I ever need it.  Parts are almost impossible to find unless you have the experience and tools to make your own.  

There are a couple other Extreme owners on the forum who I'm sure will chime in and give you the benefit of their experience.  One member.... Shadow  (aka: my buddy ED) did do a tune on his 1250 and I'm sure he can give you some great information regarding going about that......

Don't give up on the beast..... once you and the rifle "become one" you'll be glad you got her because she's an awesome hunting gun.....

Jeff

[shadow]

Welcome to the GTA FAMILY Devin happy to have you aboard. The Extremes are a Magnum shooter and can have a harshness to them that messes with the accuracy. I have tuned my 1250.22 with great result's  in accuracy and in taming the beast so to speak. What I did is de-tune it with a lighter tophat which reduces vibration along with a smoother response from the shooter. I went through the action and did a detailed debure and polish which included the mainspring, cocking lever and slot's, spring guide and area's of the piston and a little go's a long way. The tune also includes the application of the proper lubes in the right places and amount's and again a little go's a long way. James Maccari located in our "MALL" section of the forum sell's the right lubes to do the job and also sell's a piston seal that will work for the 1250. The piston seal is labeled "Walter Talon- Hunter Mag" and sell's for $12.00. Now you may have to alter the piston slightly depending on the style of piston that your Extreme has, some of a removable screw at the end and some of a step type end in which the piston seal must be modified but it will work. I found for me the key was to take all the power and manage it and the 1250 has a tophat in it that's heavy as a anchor and is part of it's magnum power but reducing the weight there also reduces the harsh recoil and temperament of the shooter. A GRT-III is a must and will greatly increase your quest for accuracy along with finding the right pellet for the shooter. Everything about the 1250 is big and tough but some TLC in the right places makes a big difference. Any questions feel free to ask I've been through my 1250 from one end to another and know her well. Ed

[customfab]

Ed,

Thanks for the input and it sounds like by you and Longislandhunter love your gun.  I'm a fairly strong boy so the weight and cocking force isn't really an issue for me.  

Can you tell me more about the lighter top hat?  

Do you happen to know if the "walter talon hunter mag" seal will require any machine work?   You mention modifications, I'm unsure if this can be accomplished at home in my shop.  I have a large array of tools (I do custom4x4 work) and even have a buddy with a CNC mil but the machine work isn't quickly avaiable to me (4 hrs away).  

[shadow]

The stock tophat which also act's as a spring guide sits inside the piston and I felt added to the harsh recoil and vibration in the action. The Tophat that I installed was machined from brass with a Delrin insert at the base. The machining was performed on a lathe , take the dimensions from the stock tophat and spin yourself one out of lighter metal's etc. I've even shaved off small slices of metal at the base of tophat's to lighten them up which also reduces the preload of the spring. I've done this on some Gamo shooters that have metal tophat's in them and have had great result's. This should be done in small step's though and may require doing it then assembling the shooter for Chrony test etc.. As far as the piston seal some Extremes have a screw in the end of the piston that can be removed to put the piston seal on with no modes. There are some pistons that have a stepped ridge that may require alteration of the piston seal. You would have to pull the action apart to see what your working with. Ed

[customfab]

Gotcha.  Do you happen to have any pics of the brass tophat with delrin insert?   I know that a internet company, http://vortekproducts.com/, offers a dual-guide system called the "pro guide 2" which is a very simple but apparently effective improvement to reducing recoil & focusing force linearly (concept seems to greatly eliminate torque or any twisted action as the spring deflects).   He actually shows the parts in his youtube video (http://www.youtube.com/watch?v=yFo8D2cABlo).   If I'm correct this dual-guide insert is simply a re-engineered tophat.  

Is your delrin insert simply pressed into your brass tophat?  

Also, you said you "shaved off small slice of metal" at the base of the tophat.    Do you recall if you are talking a few hundredths of an inch?   Has the velocity of the gun been reduced then?  I'd be curious if you had before & after chrony numbers.  

I'll have to disassembly my gun and check out the piston.   Sucks as my buddy doesn't have a lathe setup at this point so I'll have to pay a machinist.  Time to ask around.   Happen to know the diameter of the magnum seal?  I'm curious if other seals are available from others such as APEX or V-Mach that would serve as a good retrofit.  Always nice to know what options are available.  You now have my engineering mind at work!    - Devin

[shadow]

No pic's but yes it's been pressed into the tophat. The tophat's that I reduced the weight on were from the Mid range shooting Gamo's and started at a 1/8 of a inch. The 1250's tophat is extremely heavy as you will see when taking the action down. With lighter tophat's will come a drop in fps but in the case of my 1250.22 she could spare it. I don't know about that duel guide system myself but a good debure and polish of the mainspring and guides makes a world of difference. I don't know the diameter of the piston seal off hand my seals were custom spun before these seals came out through James Maccari but I'm sure you can get the spec's through e-mailing his sight or when your action is apart getting a ID of the action. Ed

[customfab]

Thanks, Ed.  Extremely helpful.  I'll let people know what I've found and done over the next few weeks.

[jeronimo]

I LOVE my extreme and havent done much to it except the new trigger.  Shoots like a dream!

[shadow]

There even sweeter with a tune, my Hunter Extreme Royal.22 is my #1 got to hunter for larger game like Bandit's, Country Rat's, G-hog's and working on trying to bag a Yote.   Ed