strange fps issue

ShadowYami · September 27th, 2010, 18:29

At the stg splat game my gun took a fit and was cased early in.

Got it home gave it a once over checking it over and giving it a nice cleaning.
Got it all back together and tried to fire it. sounded nice and healthy loaded a mag and tried shooting it at a pop can 5 feet away. No impact, as I was taking the mag out I axidently shot my foot. I didn't feel a thing I just found a bb suddenly appear between 2 toes. Clocked it and came out with 50fps with a .2. After that I gave it a whole work over checking everything from the gears to air nozzle to spring to cylinder. Everything in the mechbox was up to snuff. I even installed the replacement spring I had intended to do after the game. Clocked it again and again 50FPS. The mechbox is upgraded to the point where its got the biggest spring it can take with out busting apart. every piece is perfectly fine or working better then normal. I checked hop up and inner barrel even replaced the hop up assembly with the old but still in packaging hop up I got about a year ago. Gave the inner barrel a really good once over.

By all accounts theres nothing wrong. but it still shoots only 50fps
pre splatters it was firring a consistent 325 average (1: 323 2: 327 3: 325 4: 329 5: 321 those are the numbers I logged presplatters)
I am at the point of turning it into a wall piece but I figured at least asking for a little help could show me something I might have missed or prove to me its time to let the dieing dog sleep

ArcticFox1984 · September 29th, 2010, 18:57

Take it to a reputable guntech, or if your the adventurous type.. Something in your air seal has gone sideways.

Best to start at the front and work your way back:

Confirm your barrel is clean..

1.) Is your hopup packing broken?
2.) Is your hopup unit cracked?
3.) Is your air seal nozzel in good working order?

Assemble these 3 components with the nozzle placed into the rear of the hopup unit as it would be at the moment of compression, place your finger over the tip of the barrel and blow into the nozzle. Is there a perfect airseal?

If this hasn't helped begin inspecting your Mechbox:

Assemble your Piston, Piston head, Cylinder, Cylinder Head and Nozzle into half of your open gear box.

With the piston in the rear most position place your finger over the nozzle and push the piston forward.

Is there a perfect airseal?

Confirm that the O-rings on the piston head, cylinder head and nozzle are all in good condition.

Also be sure to confirm that your cylinder hasn't expanded like a balloon.

ShadowYami · September 29th, 2010, 21:33

would the cylinder having expanded be easy to notice or would it be something that would need a targeted look see with a magnified glass? i have the gearbox in peices atm looking it over
1 hopup packing is well new
2 does not appear cracked
and the nozzel seals look good thank god thats one of the things that cant be fixed so easily cause its a v1

And as far as gun techs are concerned I am a gear head who intends on being a guntech so if i cant fix my own guns what proof would I have in the future that I can fix some one elses. I never got into airsoft for the "games" I got in it cause I am a tinker the games are mostly an excuse to put wear on a gun so it would brake naturally so I can fix it. They are marvels of technology.

ArcticFox1984 · October 3rd, 2010, 04:03

Sorry for the late reply,

Ballooned cylinders are generally easy to spot, the cylinder would seem loosely fit to the piston assembly and provide poor airseal.

My friends M4A1 had that issue, it was semi difficult to diagnose but seemed obvious once I figured it out.

The main indicator as is usually the case is in the sound of the action, a cycle will sound much snappier when there is a major compression issue as the piston travels much faster forward when its not pushing much air, or when that air escapes to readily.

Although keep in mind; if your gun is stretching its torque capability the rate of fire may increase as more and more momentum is imparted on the gears; this should not be confused with a compression issue.

The main thing to listen for when troubleshooting inconsistent fps is inconsistent "action harmonics". This is a clear indicator that there is something funky happening in your box... if it sounds smooth and consistent its likely something in the barrel assembly... a small crack in anything is enough to do it and would only show its ugly head under high pressure.

Amos · October 3rd, 2010, 04:33

Ballooning cylinders is something that RARELY (I'm not saying never because you can never be 100% sure, but read: Rarely on the verge of never) happens, what happens is the O-ring on the piston head will shrink when it's at rest for too long and that will make it seem like the cylinder head doesn't fit well in the cylinder anymore.

ShadowYami · October 3rd, 2010, 11:35

wow after reading both posts and taking it into account. My gear box is FUCKED

I have to say arctic you were right the gun wasn't fired in a good while. Just so people can understand what I mean when I say fucked this is a disruption to the best of my ability's.

on the last dry fire out of gun for a listen i heard a rather interesting sound. from what I can figure the piston was moving loose. The spring guide snapped and then as it shot forward it made an impact on the air nozzle. No spring guide no air nozzle cylinder has this nice cut along it from getting chewed by the gears and the pistons face is now cracked.

Never thought to look for play between the piston and cylinder thanks for the tip.

I hate version ones
And for the record this all came to pass just an hour ago
Now if you will excuse me I need to see if I can't dig up a v1 air nozzle and spring guide.
the piston and cylinder is the same from a v2

ArcticFox1984 · October 4th, 2010, 04:00

Quote:

Originally Posted by Amos

Ballooning cylinders is something that RARELY (I'm not saying never because you can never be 100% sure, but read: Rarely on the verge of never) happens, what happens is the O-ring on the piston head will shrink when it's at rest for too long and that will make it seem like the cylinder head doesn't fit well in the cylinder anymore.

I've seen it a few times, but never on a reinforced cylinder... both incidents were caused by a stock type A cylinder on short barreled weapons combined with itchy trigger fingers and strong springs.

So what can you expect really.

@OP: Good luck sorting that shit out: The FAMAS is becoming an endangered species.

OMGWTF · October 4th, 2010, 13:49

Just a note... 9 times out of 10 if you're getting garbage FPS
it's an issue with your compression cycle.
With FPS Issues/compression cycle issues, first thing you want to look at is O-rings.. These maintain your airseal.

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September 27th, 2010, 18:29	#1
ShadowYami Trader rating Join Date: May 2010	strange fps issue At the stg splat game my gun took a fit and was cased early in. Got it home gave it a once over checking it over and giving it a nice cleaning. Got it all back together and tried to fire it. sounded nice and healthy loaded a mag and tried shooting it at a pop can 5 feet away. No impact, as I was taking the mag out I axidently shot my foot. I didn't feel a thing I just found a bb suddenly appear between 2 toes. Clocked it and came out with 50fps with a .2. After that I gave it a whole work over checking everything from the gears to air nozzle to spring to cylinder. Everything in the mechbox was up to snuff. I even installed the replacement spring I had intended to do after the game. Clocked it again and again 50FPS. The mechbox is upgraded to the point where its got the biggest spring it can take with out busting apart. every piece is perfectly fine or working better then normal. I checked hop up and inner barrel even replaced the hop up assembly with the old but still in packaging hop up I got about a year ago. Gave the inner barrel a really good once over. By all accounts theres nothing wrong. but it still shoots only 50fps pre splatters it was firring a consistent 325 average (1: 323 2: 327 3: 325 4: 329 5: 321 those are the numbers I logged presplatters) I am at the point of turning it into a wall piece but I figured at least asking for a little help could show me something I might have missed or prove to me its time to let the dieing dog sleep __________________ Its still alive? It should be dead by now. The famass that will not die. It only ever gets used because it has not fired its last shot yet. When I can't patch it up its going to be hung on the wall like a good version 1.

September 29th, 2010, 21:33	#3
ShadowYami Trader rating Join Date: May 2010	would the cylinder having expanded be easy to notice or would it be something that would need a targeted look see with a magnified glass? i have the gearbox in peices atm looking it over 1 hopup packing is well new 2 does not appear cracked and the nozzel seals look good thank god thats one of the things that cant be fixed so easily cause its a v1 And as far as gun techs are concerned I am a gear head who intends on being a guntech so if i cant fix my own guns what proof would I have in the future that I can fix some one elses. I never got into airsoft for the "games" I got in it cause I am a tinker the games are mostly an excuse to put wear on a gun so it would brake naturally so I can fix it. They are marvels of technology. __________________ Its still alive? It should be dead by now. The famass that will not die. It only ever gets used because it has not fired its last shot yet. When I can't patch it up its going to be hung on the wall like a good version 1.

October 3rd, 2010, 04:33	#5
Amos Trader rating Join Date: Aug 2006 Location: Japan	Ballooning cylinders is something that RARELY (I'm not saying never because you can never be 100% sure, but read: Rarely on the verge of never) happens, what happens is the O-ring on the piston head will shrink when it's at rest for too long and that will make it seem like the cylinder head doesn't fit well in the cylinder anymore. __________________ Custom Builds: FA3674U Krinkov G3SD6

September 29th, 2010, 18:57	#2
ArcticFox1984 Trader rating Join Date: Feb 2007 Location: Toronto, Ontario	Take it to a reputable guntech, or if your the adventurous type.. Something in your air seal has gone sideways. Best to start at the front and work your way back: Confirm your barrel is clean.. 1.) Is your hopup packing broken? 2.) Is your hopup unit cracked? 3.) Is your air seal nozzel in good working order? Assemble these 3 components with the nozzle placed into the rear of the hopup unit as it would be at the moment of compression, place your finger over the tip of the barrel and blow into the nozzle. Is there a perfect airseal? If this hasn't helped begin inspecting your Mechbox: Assemble your Piston, Piston head, Cylinder, Cylinder Head and Nozzle into half of your open gear box. With the piston in the rear most position place your finger over the nozzle and push the piston forward. Is there a perfect airseal? Confirm that the O-rings on the piston head, cylinder head and nozzle are all in good condition. Also be sure to confirm that your cylinder hasn't expanded like a balloon.

October 3rd, 2010, 04:03	#4
ArcticFox1984 Trader rating Join Date: Feb 2007 Location: Toronto, Ontario	Sorry for the late reply, Ballooned cylinders are generally easy to spot, the cylinder would seem loosely fit to the piston assembly and provide poor airseal. My friends M4A1 had that issue, it was semi difficult to diagnose but seemed obvious once I figured it out. The main indicator as is usually the case is in the sound of the action, a cycle will sound much snappier when there is a major compression issue as the piston travels much faster forward when its not pushing much air, or when that air escapes to readily. Although keep in mind; if your gun is stretching its torque capability the rate of fire may increase as more and more momentum is imparted on the gears; this should not be confused with a compression issue. The main thing to listen for when troubleshooting inconsistent fps is inconsistent "action harmonics". This is a clear indicator that there is something funky happening in your box... if it sounds smooth and consistent its likely something in the barrel assembly... a small crack in anything is enough to do it and would only show its ugly head under high pressure.

October 3rd, 2010, 11:35	#6
ShadowYami Trader rating Join Date: May 2010	wow after reading both posts and taking it into account. My gear box is FUCKED I have to say arctic you were right the gun wasn't fired in a good while. Just so people can understand what I mean when I say fucked this is a disruption to the best of my ability's. on the last dry fire out of gun for a listen i heard a rather interesting sound. from what I can figure the piston was moving loose. The spring guide snapped and then as it shot forward it made an impact on the air nozzle. No spring guide no air nozzle cylinder has this nice cut along it from getting chewed by the gears and the pistons face is now cracked. Never thought to look for play between the piston and cylinder thanks for the tip. I hate version ones And for the record this all came to pass just an hour ago Now if you will excuse me I need to see if I can't dig up a v1 air nozzle and spring guide. the piston and cylinder is the same from a v2 __________________ Its still alive? It should be dead by now. The famass that will not die. It only ever gets used because it has not fired its last shot yet. When I can't patch it up its going to be hung on the wall like a good version 1.

October 4th, 2010, 13:49	#8
OMGWTF Trader rating Join Date: Jun 2010 Location: Yellowknife, NWT	Just a note... 9 times out of 10 if you're getting garbage FPS it's an issue with your compression cycle. With FPS Issues/compression cycle issues, first thing you want to look at is O-rings.. These maintain your airseal.

strange fps issue

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