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Discussion Starter · #1 · (Edited)
Hi guys,

I would like to ask your help to find the problem in my G&G GR25 that does not have enough range.
The stock barrel had a hard scratch so had to be replaced.
In the meantime also wanted to tune up to our field limits: 500FPS (0.2g)
So changed the spring and the barrel only:
Had a shorter Guarder brass tightbore 6.02 /469mm around so put it in with a stronger spring.
The gun shoots consistent 465FPS (+/-2) but has weak range.
It shoots only around 45m effective with 0.36 madbull BB.

Tried with a wider barell just to test: Cyma 6.08/ 509mm: it has higher around 485FPS. strange... And still the same range! so no big change.
Gun has been taken to parts. All parts seems to be fine.

Any idea what might cause this? Barrel, length, width, volume? What should I check, change, try?
many thanks!
 

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I agree with Thenoob. There must be an issue with the hop. At those velocities, and firing .36's, you should be getting at least 70m effective. At LEAST. I wonder if the hop is on at all or actually doing anything? What does the flight path of the BB look like? Does it lift or drop steadily on the way out of the barrel?
 

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Discussion Starter · #4 · (Edited)
yes, I also expected minimum 70m eff. range... :(
Already tried with many different hopup rubbers soft to hard. now a Maple leaf 70 is installed with flathop. Flight path seems ok. hop works as it should. still no range.
does anyone use it with close to 500 FPS with harder spring? (120-150?) May be too much for stock setup? Now wondering to put back a weaker spring close to 400Fps...
Heard of any issue with the barrel size or length? (though it does have same issue with tight bore, normal bore, shorter, normal) thx
 

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Discussion Starter · #9 ·
sounds great with 405fps! I just want to achive that 80 yards effective...whatever the fps is :)
have you tried what it does with higher close to 500?
can you please send your build, what are your internal parts?
 

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Unfortunately there's not a whole lot of secret parts in it. Most of it is hand work. R hop, home made mosfet, altered bucking, and a whole lot of careful fitting. Most of the internal parts are stock including the barrel. The magic is in the hop. It's heavily modified. Different length, radius, etc. Gears are stock, piston is stock, I use an M110 spring and a 9.6v nunchuck. The magic is in how the spring releases and how efficient the hop is.

Something a lot of people forget is that with more fps you need more BB. At 405fps, a 0.3 works really well with an r hop. At 450 fps, I get good results with .4's. hotter than that and they go off course. You can 'over clock' a BB. It's just a little plastic ball. The path and distance of the BB is dependant on how the spin is induced and the duration. None of that comes in a kit. You have to tune it.

Any gun here with an electric motor is regulated to 420 fps and under. Because it has the potential to be made full auto, it's capped. Bolt guns can go to 500 fps here, but even then, there isn't much advantage considering the weight of ammo available and the terrain we play on. In this part of the world, with heavy foliage and such, we do need penetrating power to get through leaves, but the likelihood of getting 250 feet in a straight line through the trees is almost impossible. So, more importantly than overall distance, the BB needs to fly absolutely straight and predictably every time. That comes from tuning.

There's a misconception about what people do to a gearbox will matter. In a way it does, but in a semi auto rifle, it simply provides a measured and timed shot of air. That's it. Nothing more. The effectiveness of the shot is all in the front end of the rifle. taking that measured shot of air and maximising the transference of energy to the BB...there's the magic. :)

Oh, and by the way, 500 fps is getting ridiculous. Somebody's going to get hurt.
 

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Discussion Starter · #11 ·
I try to use different cylinder/barrel/bb weight ratio. GG Gr25 has the small standard M4 cylinder size and with current setup it seems unefficient (undervolumed) with 1,7 ratio. So the inner barrel seems too long. With 500FPS using 0,36 bb ideal barrel lenght should be around 380mm getting 2,5 cylinder/barrel ratio. So will cut the barrel shorter and see the results.
 

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In weekend airsoft games there was a kid that had a g36 shooting 2 joules but didn't fly further than 40m and didn't even hurt (refs tested it).
 

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Wow...those BB's were losing energy FAST! hahahaha. Actually, you can get that phenomena with a very light BB, or a very cranked down hop unit. They come out smokin hot and just drop. 40m is pretty bad...no, really bad. Unfortunately..
 

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There's probably nothing wrong with the hop itself, but more than likely the bucking or the nub, or a combination of a couple of things. The stock metal hop up unit is actually ok. If it's shooting doubles, check for a blockage of some kind in there. The problem is definitely in the barrel group. Too bad I can't check it in person! Sorry about that...
 
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