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Sedole

CYMA m14

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So, like the topic says, I want to bring my CYMA m14 up to 450 fps on a .20g bb while having it be reliable(not break down after a few thousand shots).

 

This is my gun currently:

DSCN4621.jpg

 

But recently...

 

I really don't know how it happened, the gun has seen a lot in it's 3 and a half year life though. Several 10's of thousands of rounds through it including many thousands of dry-fires, 2 years shooting 415+ fps, 1 year and a half shooting 400 fps. It's been through a lot; rain, mud, abusive friends, drops from a few feet off the ground(several drops), etc.

 

I noticed very sporadic compression when I chronographed it last weekend (shots varying from 200fps to 400 fps). So I took it apart, and saw this.. :a-confused:

33937_167455186601281_100000104035217_569796_3113948_n.jpg

33894_167455086601291_100000104035217_569794_168932_n.jpg

 

Everything else on the gun works fine, and it still runs, just the gearbox shell is trash.

 

So to take my gun to near or slightly under 450 fps on a .20g bb, what parts should I add in addition to a Systema M130 spring? (or will that spring even get me up to 450?)

 

I currently run an intellect 9.6v battery, prometheus air nozzle with o-ring, quarder shims, metal spring guide with ball bearings by guarder, and a kwa 2gx bucking.

 

Note: I bought it as a new aftermath m14(I know, I know, nooby mistake, but I was only 1 year into airsofting and didn't know much) and it came shooting above 400 fps according to the poor man's chrono and after 2 years of use, I finally got it actually chronoed at 400fps. Aftermath claimed it comes shooting 500 fps. I know that's bs, and most likely with a .12g bb.

 

So what parts should I add so that my gun can handle the 450 fps under plan A or plan B?

 

Plan A:

I buy a full-sized cyma m14 from the airsoftgi boneyard to get an intact gearbox shell and to convert my m14 to the full sized version(since I think it looks better) for around $50-60.

 

Note: I don't want to buy a tightbore barrel, even a cheap madbull one, the stock tightbore gave me satisfactory accuracy and range.

 

Pros:

Ability to switch upper receivers for different scenarios

I like the look of the full size m14

threads on the end of the barrel (socom doesn't have threads)

 

Cons:

I know the version 7 gearbox is one of the strongest, but can the CYMA gearbox shell even handle the 450 fps?

 

Plan B:

Get the G&P version 7 gearbox for $100.

G&P

 

I know evike isn't the most reliable source to buy things from, and I always buy from airsoftgi, but I couldn't find this elsewhere.

 

Pros:

I'm assuming it's stronger than the CYMA gearbox shell?

Comes with a spur gear (assuming it's better than CYMA's?)

Comes with a piston (assuming it's better than CYMA's?)

Also comes with 7mm ball bearing bushings

 

Cons:

Is it even better than the CYMA?

Doesn't get me the full length m14 look, but it's not too big of a deal

 

So, with what plan (A or B) can I get to my targeted fps cheapest? Also with either plan, if I have to add reinforced parts, what parts in specific should I add(post links please)? Or if you have another plan that sounds better, please state it.

 

Note: I do all the gearbox work myself. I tech my own and my friends guns and am very comfortable with version 7 gearboxes(version 2's as well), I don't have to use any youtube video guides or anything. I can also solder and weld and have tools to do it with. :a-wink:

 

I would like to maintain a budget of $150 excluding shipping and taxes, but I know that will be very difficult to reach. Unless I could get something off of the airsoftgi shocker deals or something of similar sale nature.

 

Thanks in advance for the advice!

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check the o ring on the air valve(I think). check the air nozzle. personally 400 with .2s is a lot. try using .25s and you'll see a big different range, accuracy, and consistency wise. maybe the motor is dead and it can't bring the spring back fully every time you shoot.

 

Did you read the post? The compression issue probably has something to do with the fact that a huge chunk of the gearbox shell is missing. If the motor wasn't pulling the spring back all the way then the gun wouldn't be shooting at all...Do you know how an AEG works?

 

I would go with option B. The CYMA shell should be able to handle a sp130/m140 reliably. You can also use sorbo pads to reduce stress on the shell. I totally agree with you on keeping the stock barrel. I run stock barrels in all my guns. Plus, CYMA actually makes pretty decent barrels.

Edited by 6mm man

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there is no reason to buy an expensive v7 gearbox shell when the cyma will work just as well. Its not a v2 where aftermarket shells are reinforced, they are all basically the same. The compression issue is definetly based on the chunk of the gearbox missing. The G&P gearbox also uses a different length motor from almost every other gearbox. It uses a middle type motor shaft

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Guarder 130 spring with good compression should get you right there or close. Going over to a 140 or larger may require more re-enforcement etc. Currently one of my M4s is shooting ~440 with a M130 and a 6.03 barrel. If that's not close enough you'll have to go over to a 140 but with a standard gear set, I think you are asking for trouble.

 

Personally I like the idea of having a boneyard gun around to rob parts from, but it really depends on what's wrong with the boneyard one to begin with. If it has say a stripped gear, and your gears are in good shape, then you're good to go plus you'll have a ton of parts to mix and match for the best setup. If the boneyard gun has a cracked gearbox, then well you're SOL and you'll have to buy a new shell.

 

 

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The boneyard would be better, you'd get a full set of replacements parts and it'd likely be cheaper.

 

And actually, the compression could be something else. The cylinder seals up with the cylinder head, not the GB shell. Sure it could very well be the problem, but unless the shell has warped and is pulling something out of place the piston head, cylinder, and cylinder head should all be sealing properly. Of course, there's also the nozzle. If I were you I'd pull the cylinder/piston/head out and check that compression, then buy a CYMA boneyard gun.

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Well the crack was leaking air, since the cylinder head was slightly at an angle.

Also, if you look closely in the first picture of the gearbox, there was a fracture.

65911_168832323130234_100000104035217_578378_1644363_n.jpg

When I opened the gearbox, instead of the spring guide trying to shoot back at me, the cylinder head just broke the rest of the gearbox shell.

 

I just decided to get a boneyard CYMA m14.

Worked out pretty well actually, $50 for a full functional m14 just missing a flash hider and bolt. So I switched out some of the externals and dropped in the prometheus air nozzle, kwa 2gx bucking, metal spring guide w/ bearings, shims, and a guarder sp120 I had lying around in a pile up stuff that never ended up in a gun. I'm getting great compression now as well.

 

I left everything else stock. I figure that if the CYMA AKs can take the 450 fps they come at on their stock pistons, this should be able to as well.

 

I have yet to chronograph it since I don't own one, but I'll take it in to my local shop and have them chrono it for me.

I'm glad I went this route, now I have 2 stocks, and 2 upper receivers to choose from. Depending on the terrain I'll be playing in.

33562_168808773132589_100000104035217_577928_5312133_n.jpg

69405_168802076466592_100000104035217_577878_8155070_n.jpg

 

Thanks for the advice!

Edited by Sedole

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Alright guys, good news and bad news;

good news; my m14 is up and running very smoothly, and I got her chronoed.

bad news; she chronoed at 385-399 fps..and that's with nearly perfect compression in the cylinder assembly compression area and a Guarder sp120 spring, which according to the airsoft canada spring chart, should be around 428.

 

also my range is horrendous. The MAX range (hop-up on all the way, shooting level) is about 150 feet until the bb touches the ground. There seems to be almost no hop at all, all the way off to all the way on there is almost no effect on the bb (maybe an increase of 10 or so feet).

 

So I have a couple of ideas on what could be wrong, the prometheus air nozzle doesn't fit well with the hop-up assembly, the kwa 2gx bucking, I'm using my old m14's hop-up (it's a cyma). Ohh and I'm positive that the hop-up nub is in, I held the barrel up to the light and pressed down on the hop-up lever to be sure that it was working, and it was (before I finished assembly)

 

So first I'll try the stock cyma bucking on the old hop-up assembly. then I'll try the new hop-up assembly w/ the 2gx bucking(it has a small deformity on the tube that feeds the bb's in), then the new hop-up assembly with the cyma bucking. And last I'll try the stock air nozzle with all the above combinations.

 

But has anyone used the prometheus air nozzle with their cyma m14 and gotten a loss of fps?

 

First I'll try

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Problem solved: the culprit was the kwa 2gx bucking and the old hop-up assembly. I couldn't take the gun back to get chronoed again since they close at 6pm, but I used the poor man's can chrono and was able to fully penetrate the bottom edge of the can. It could not penetrate the top center, but was able to make a big indentation with a crack about half of the size of a bb in it.

 

I also noticed a major increase of range. I paced out the distance I was shooting to be around 190-210 feet. I was shooting at a wooden gate about 4ft wide by maybe 6ft tall. Hit it 9/10 times with one flyer

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Problem solved: the culprit was the kwa 2gx bucking and the old hop-up assembly. I couldn't take the gun back to get chronoed again since they close at 6pm, but I used the poor man's can chrono and was able to fully penetrate the bottom edge of the can. It could not penetrate the top center, but was able to make a big indentation with a crack about half of the size of a bb in it.

 

I also noticed a major increase of range. I paced out the distance I was shooting to be around 190-210 feet. I was shooting at a wooden gate about 4ft wide by maybe 6ft tall. Hit it 9/10 times with one flyer

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