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Gamo Gamo Magnum GR (.25 cal) very inaccurate?

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Franco777

Member
Nov 14, 2023
2
1
Carlisle, PA, USA
2 months ago I purchased a Gamo Magnum GR in .25 caliber. It is a springer... not a ram air. I have shot about 700 rounds through it... using many different varieties of pellets. It seems to like the Diablo Exact King 25.39 grain the best but... even when shooting off of a bench rest, I can't get groups of less than 6 inches at 40 yards. (Maybe 5 inches if I exclude the worst shot). It seems to be very inaccurate. The power is out of this world though.

My 1980 Feinwerkbau Sport 124 (.177 caliber) shoots so much more accurately than this Gamo Magnum GR. Does anyone have any suggestions as to how to improve the accuracy? (Note that all screws on both the rifle and the scope are tight. The trigger is set to about 1-1/2 pounds).
 
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Franco777 said:
2 months ago I purchased a Gamo Magnum GR in .25 caliber. It is a springer... not a ram air. I have shot about 700 rounds through it... using many different varieties of pellets. It seems to like the Diablo Exact King 25.39 grain the best but... even when shooting off of a bench rest, I can't get groups of less than 6 inches at 40 yards. (Maybe 5 inches if I exclude the worst shot). It seems to be very inaccurate. The power is out of this world though.

My 1980 Feinwerkbau Sport 124 (.177 caliber) shoots so much more accurately than this Gamo Magnum GR. Does anyone have any suggestions as to how to improve the accuracy? (Note that all screws on both the rifle and the scope are tight. The trigger is set to about 1-1/2 pounds).
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Gamo barrels are pretty poopty quality. I think you need to polish your barrel or/and re-crown it.
 
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The rest may not be allowing the springer to recoil naturally. Take a towel and roll it up and use that as a rest. This will allow for natural movement. Of course with a magnum springer, you need to have consistent cheek weld, hand placement, etc, etc. Dont 'grip' the stock and 'squeeze' the trigger... rather, palm it and pull as straight back on the trigger as you can. Consistency is key.
 
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Thanks, everyone, for the replies and advice. My Gamo Magnum GR (.25 cal) is only 2 months old. I have shot about 750 rounds through it. I clean the barrel after each 200 rounds but someone (not in this forum) advised me not to. They said to let the lead build up in the barrel. I am not sure about that advice.
As far as shooting "off the irons", the synthetic stock on this rifle has an extremely high cheek piece that precludes comfortably using the iron sights. This stock is very poorly designed. Otherwise, those sights seem like they would be very good. If you are shooting with a scope (I replaced my Gamo scope with a Leapers 3-12x44 mil dot scope) then the cheek piece shape of the stock is not a problem. So I always shoot through the scope.
As advised, I will try to let the rifle recoil naturally when I shoot it. I'd really like to get it down to 2 inch groups at 50 yards. I don't want to hunt with it and just be wounding animals (mostly ground hogs). I need head shots.
Thanks again everyone. I'm new to Air Gun Nation but you all seem to be a great bunch of folks. Very helpful!
 
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My gamo whisper fusion mach 1 .22 took forever to settle . I almost gave up on it. .. then it got good and real good one day. Became my 2ed favorite ..

I clean my barrels about 250 shots and try not to let one go over 500.. where else do you see a filthy barrel make a accurate gun ? Just in the air gun forums ..lol. Everyone's got there thing they do so you do as you find best in the end
 
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Hateful McNasty said:
My gamo whisper fusion mach 1 .22 took forever to settle . I almost gave up on it. .. then it got good and real good one day. Became my 2ed favorite ..

I clean my barrels about 250 shots and try not to let one go over 500.. where else do you see a filthy barrel make a accurate gun ? Just in the air gun forums ..lol. Everyone's got there thing they do so you do as you find best in the end
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Polishing barrel with paste is shortcut what I took after 1000 shots xD
 
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It might be comparing apples to oranges, but I have a Gamo Swarm Magnum gen1 (.22) that shoots fantastic. Zero'd at 40 yards and while rested it's sub .5" accurate at that distance. Gamo can make some good shooters, I know not all have had the same experience, sometimes sub par product is released from any and all manufacturers time to time.

Testing with a different optic or open sights is solid advice. I know the comb height is high, but if you adjust the rear sight so it can be used, even if not "on" at a certain distance it could give you an idea of how it's grouping. Take a long sheet of cardboard or cut up a box to get maybe 18" to 24" tall or more, then draw or post a target on the very bottom to aim at and shoot. Make sure to have a safe backstop... Or just try a different scope. Otherwise you're playing a guessing (and exchanging) game of if it's the gun, optic (or even the shooter 😮 😜) ...causing poor accuracy.

If it still groups poorly after changing holds and optic/irons, I'd seek an exchange.
(or figure a way to get closer to my quarry, like a ninja 😏).
 
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Probably not the issue but have you checked the barrel tension? On an older Gamo I had, it initially was under tightened and loose. I added a shim and tightened it up and got better results.

Most Gamo barrels are pretty accurate. Gamo tends to over spring their guns. I've detuned a few Gamo Hunter 440s for friends and they go from twangy jumpers to mild manner tack drivers.

Hopefully you can get it worked out. Def frustrating when your chasing accuracy.
 
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(F)Airgunner said:
May be a worth of trying.
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The symptoms my gun had were extreme differences in velocity from shot to shot, up to 150 fps. I was chronographing it, so this was evident to me and probably wouldn't have been to 90% of purchasers. What I noticed was certain locations on the magazine gave full power shots and certain positions were low. It was almost like a PCP shot curve. The shots on a Gamo magazine are visually numbered and #10 would be pretty good. #9, 8 and 7 would be close to ideal and every shot after that would get progressively worse. I suspected it was a bad magazine so I ordered 2 more and they both had similar problems too.

Fortunately, removing the magazine mechanism is very easy and once I did so my velocities improved even over the good magazine locations and the consistency settled down to about a 30 fps range.

The magazine feed is really a kludgy, cheaply built sort of mechanism. It's amazing in a way that this very cheap and mostly plastic mechanism can rotate 90 degrees into position, feed a pellet, rotate back out of position and then advance once a shot is fired. It's just expecting way too much mechanical precision out of a very inexpensive mechanism.
 
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xsarfc9x said:
Probably not the issue but have you checked the barrel tension? On an older Gamo I had, it initially was under tightened and loose. I added a shim and tightened it up and got better results.

Most Gamo barrels are pretty accurate. Gamo tends to over spring their guns. I've detuned a few Gamo Hunter 440s for friends and they go from twangy jumpers to mild manner tack drivers.

Hopefully you can get it worked out. Def frustrating when your chasing accuracy.
Click to expand...
Btw, is there any chance to remove swarm magnum 10x barrel? Im scared of breaking it when I try to remove it and havent really tried with full effort.
 
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