For the EXPERTS in fps loss

Spa · April 2nd, 2007, 15:13

Recently for my CA M249, i just cleaned out the barrel and put the hop up back together properly and i lost 120 fps... The gun doctors of manitoba have no idea what is wrong with the lmg and i have been working on it switching 1 part at a time in and out of it.

MY question is, What are the many sources of FPS loss in an AEG, and with this knowledge ill be able to continue testing it to figure out the problem.

Here are a list a parts in the 249:

Systema alum piston head
CA reenforced piston
systema area 1000 cylinder head
CA o-ring nozzle
systema v2 spring guide
(depends on the event) systemaM100 and M120 springs

I hope this helps, as i need to figure this problem out!

Thank you!

Spa

Greylocks · April 2nd, 2007, 15:33

Loss of fps relates to a loss of air pressure someplace along the way, and the power of the spring (volume of air moved rapidly does matter).

So look at the parts involved in air pressure loss.

Is the spring ok? Is the cylinder ok? The nozzle? The piston's o-ring? The hopup? The barrel itself?

It could be as simple as a .25 cents o-ring.

mcguyver · April 2nd, 2007, 15:34

Perhaps your piston head o-ring is not sealing against the cylinder wall like it should. They are easy to test at slow speed, as you can seal off the nozzle with your finger while you push the piston in the cylinder. But this is not always indicative of its performance at high speed. Ther can be slight dimensional differences between cylinders from one manufacturer to another, and this doesn't help matters at all.

Also, the lube for the cylinder should not be lithium (the white gunk) as it is a very viscous lube and has a bad tendency to gum-up. You should try CA's silicone-based cylinder lube. It is much less viscous and is really what should be used in cylinders anyways.

Spa · April 2nd, 2007, 15:39

I did change the o ring on the Pison head and there was pressure when i tested it by putting my finger on the sylinder head and did notice that there pressure.

It just bugs me that I put a better nozzle on the M249 then the stock one and the FPS dropped by 120, but in this operation i also took apart my hopup the clean the barrel.

could the hop up take away from the fps aswell?

and the parts are all in mint condition, most of them brand new.

but i will invest in some cylinder gease to see if it helps.

CDN_Stalker · April 2nd, 2007, 15:55

Apoc had the same problem, fps loss from changing the hop up rubber, and he eventually fixed it by over lubing the pistonhead O-ring (I know, I still laugh at him for doing it and for having to run like 30 patches through his barrel to clear the grease out) but it shoots hard and consistant now.

ILLusion · April 2nd, 2007, 15:58

You might also want to check your hop up level... I've seen huge FPS losses from having your hop up turned up too high.

Spa · April 2nd, 2007, 16:02

Yeah, I made sure that the hop level was just enough to hold the BB in place, but jsut enough not to decrease fps to much.

Yesterday when i put the new nozzle in, i tested the fps with medium hop up and no hop up, and the fps was still the same. The little clear palstic part that gets pushed into the barrel to create the grip was ripped a bit but it still does put pressure on the black rubber that comes into the barrel chamber...so im no to concerned with that.

If cylidner grease is what i need lets hope it works. ill go pick soem up today and let you guys know:P

Greylocks · April 2nd, 2007, 16:12

From what you just said, it sounds more like a hopup problem. Ripped just a bit? Any amount of problems with your hopup will follow through and make your life hell.

Otherwise, there is an air-seal problem somewhere in there.

Spa · April 2nd, 2007, 16:14

I dont think that 3mm clear plastic thats gets pushed up from turning the hop up will have nothing to do with air pressure, my assumptions from this are because it is exterrior of the barrel, and if not even used will have nothing to do with the barrel:P

I should take pictures and post them to show you guys:P

Eyeball (Green7) · April 2nd, 2007, 16:28

I'm absolutely not an expert, but i reassembled my EAG once (bough it dissassembled) and one thing comes to mind,
you said you changed the air nozzle, I dont Know if there is differences between different EAGs but if it's not the right one it can be that it's not sealing with the barrel properly so there could be a lost there...
but correct me if i'm wrong, it's just a guess...

Dan

Skruface · April 2nd, 2007, 16:58

Problems could include:

Piston head o-ring leakage: Soak it in 100% pure silicone oil overnight. Or, try a larger/thicker o-ring.

Nozzle o-ring: check to make sure it's still there, and soak it as mentioned above. A dental pick is a great way to get it in/out.

Hopup rubber - if it's torn, it leaks air and needs to be replaced. Replace it, and you could also try a single wrap of teflon tape around the outside of the hopup rubber/barrel to minimize air leakage.

Piston head - it's plastic - it may have a nick or be out-of-round. Check it.

Cylinder - is it a full cylinder (no holes) or a ported cylinder? If it has holes, make sure the holes are at the back, not the front.

Spa · April 2nd, 2007, 16:59

All nozzle diameters are the same, its the length of the nozzle that is different with the AEG's to let the BB's enter then chamber when the tappet plate pulls it back.

I hope to god that the issue is not the nozzle im almost 80% sure that it could not be the problem. But all in all, fixing an AEG is a lengthy process testing each part 1 at a time to identify the problem.

I will check the o-rngs on all the parts again. and i will definatly re assess the hop up. ill get back to everyone tommrow

ILLusion · April 2nd, 2007, 18:55

Best way to check to see if it's the nozzle is to toss the old one back in and see if the velocity jumps up. If it does, you'll need to carefully inspect the new one and figure out what the bugger is going on.

Spa · April 3rd, 2007, 01:14

ya illusion, thats exactly what i was going to do:P i wish i owne da cronograph to help test these things so im gonan have to wait till out indoor facility opens up so i can go work on it there to figure out the problem.

mcguyver · April 3rd, 2007, 01:18

Use a popcan. Works reasonably well.

Under 320 fps - no penetration
320-360 penetrates one side only
360-400 penetrates both sides
400-430 penetrates bottom only
430-480 penetrates top only
500+ penetrates top and bottom

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April 2nd, 2007, 15:13	#1
Spa Trader rating Join Date: Oct 2006 Location: Winnipeg, Manitoba	For the EXPERTS in fps loss Recently for my CA M249, i just cleaned out the barrel and put the hop up back together properly and i lost 120 fps... The gun doctors of manitoba have no idea what is wrong with the lmg and i have been working on it switching 1 part at a time in and out of it. MY question is, What are the many sources of FPS loss in an AEG, and with this knowledge ill be able to continue testing it to figure out the problem. Here are a list a parts in the 249: Systema alum piston head CA reenforced piston systema area 1000 cylinder head CA o-ring nozzle systema v2 spring guide (depends on the event) systemaM100 and M120 springs I hope this helps, as i need to figure this problem out! Thank you! Spa

April 2nd, 2007, 15:34	#3
mcguyver Trader rating Join Date: Aug 2005 Location: Northern Alberta	Perhaps your piston head o-ring is not sealing against the cylinder wall like it should. They are easy to test at slow speed, as you can seal off the nozzle with your finger while you push the piston in the cylinder. But this is not always indicative of its performance at high speed. Ther can be slight dimensional differences between cylinders from one manufacturer to another, and this doesn't help matters at all. Also, the lube for the cylinder should not be lithium (the white gunk) as it is a very viscous lube and has a bad tendency to gum-up. You should try CA's silicone-based cylinder lube. It is much less viscous and is really what should be used in cylinders anyways. __________________ Age verifier Northern Alberta Democracy is two wolves and a sheep discussing what's for dinner. Freedom is the wolves limping away while the sheep reloads. Never confuse freedom with democracy.

April 2nd, 2007, 15:39	#4
Spa Trader rating Join Date: Oct 2006 Location: Winnipeg, Manitoba	I did change the o ring on the Pison head and there was pressure when i tested it by putting my finger on the sylinder head and did notice that there pressure. It just bugs me that I put a better nozzle on the M249 then the stock one and the FPS dropped by 120, but in this operation i also took apart my hopup the clean the barrel. could the hop up take away from the fps aswell? and the parts are all in mint condition, most of them brand new. but i will invest in some cylinder gease to see if it helps. Last edited by Spa; April 2nd, 2007 at 15:41..

April 2nd, 2007, 15:33	#2
Greylocks Trader rating Join Date: Dec 2001 Location: Gatineau, Quebec (Near Ottawa)	Loss of fps relates to a loss of air pressure someplace along the way, and the power of the spring (volume of air moved rapidly does matter). So look at the parts involved in air pressure loss. Is the spring ok? Is the cylinder ok? The nozzle? The piston's o-ring? The hopup? The barrel itself? It could be as simple as a .25 cents o-ring.

April 2nd, 2007, 15:55	#5
CDN_Stalker Official ASC Bladesmith Trader rating Join Date: Jul 2003 Location: Ottawa, Ont.	Apoc had the same problem, fps loss from changing the hop up rubber, and he eventually fixed it by over lubing the pistonhead O-ring (I know, I still laugh at him for doing it and for having to run like 30 patches through his barrel to clear the grease out) but it shoots hard and consistant now. __________________ STKR Knives http://www.facebook.com/#!/pages/STK...17036668380871

April 2nd, 2007, 15:58	#6
ILLusion GBB Whisperer Trader rating Join Date: Jun 2002 Location: Toronto	You might also want to check your hop up level... I've seen huge FPS losses from having your hop up turned up too high. __________________ *Advanced Airsoft Armaments and Enhancements* Quick to the gun, sure of your grip. Quick to the threat, sure of your shot. Diligentia, Vis, Celeritas Accuracy, Power, Speed

April 2nd, 2007, 16:02	#7
Spa Trader rating Join Date: Oct 2006 Location: Winnipeg, Manitoba	Yeah, I made sure that the hop level was just enough to hold the BB in place, but jsut enough not to decrease fps to much. Yesterday when i put the new nozzle in, i tested the fps with medium hop up and no hop up, and the fps was still the same. The little clear palstic part that gets pushed into the barrel to create the grip was ripped a bit but it still does put pressure on the black rubber that comes into the barrel chamber...so im no to concerned with that. If cylidner grease is what i need lets hope it works. ill go pick soem up today and let you guys know:P

April 2nd, 2007, 16:12	#8
Greylocks Trader rating Join Date: Dec 2001 Location: Gatineau, Quebec (Near Ottawa)	From what you just said, it sounds more like a hopup problem. Ripped just a bit? Any amount of problems with your hopup will follow through and make your life hell. Otherwise, there is an air-seal problem somewhere in there.

April 2nd, 2007, 16:14	#9
Spa Trader rating Join Date: Oct 2006 Location: Winnipeg, Manitoba	I dont think that 3mm clear plastic thats gets pushed up from turning the hop up will have nothing to do with air pressure, my assumptions from this are because it is exterrior of the barrel, and if not even used will have nothing to do with the barrel:P I should take pictures and post them to show you guys:P

April 2nd, 2007, 16:28	#10
Eyeball (Green7) Trader rating Join Date: Jul 2006 Location: Trois-Rivières, Qc	I'm absolutely not an expert, but i reassembled my EAG once (bough it dissassembled) and one thing comes to mind, you said you changed the air nozzle, I dont Know if there is differences between different EAGs but if it's not the right one it can be that it's not sealing with the barrel properly so there could be a lost there... but correct me if i'm wrong, it's just a guess... Dan __________________

April 2nd, 2007, 16:59	#12
Spa Trader rating Join Date: Oct 2006 Location: Winnipeg, Manitoba	All nozzle diameters are the same, its the length of the nozzle that is different with the AEG's to let the BB's enter then chamber when the tappet plate pulls it back. I hope to god that the issue is not the nozzle im almost 80% sure that it could not be the problem. But all in all, fixing an AEG is a lengthy process testing each part 1 at a time to identify the problem. I will check the o-rngs on all the parts again. and i will definatly re assess the hop up. ill get back to everyone tommrow

April 2nd, 2007, 18:55	#13
ILLusion GBB Whisperer Trader rating Join Date: Jun 2002 Location: Toronto	Best way to check to see if it's the nozzle is to toss the old one back in and see if the velocity jumps up. If it does, you'll need to carefully inspect the new one and figure out what the bugger is going on. __________________ *Advanced Airsoft Armaments and Enhancements* Quick to the gun, sure of your grip. Quick to the threat, sure of your shot. Diligentia, Vis, Celeritas Accuracy, Power, Speed

April 3rd, 2007, 01:14	#14
Spa Trader rating Join Date: Oct 2006 Location: Winnipeg, Manitoba	ya illusion, thats exactly what i was going to do:P i wish i owne da cronograph to help test these things so im gonan have to wait till out indoor facility opens up so i can go work on it there to figure out the problem.

April 3rd, 2007, 01:18	#15
mcguyver Trader rating Join Date: Aug 2005 Location: Northern Alberta	Use a popcan. Works reasonably well. Under 320 fps - no penetration 320-360 penetrates one side only 360-400 penetrates both sides 400-430 penetrates bottom only 430-480 penetrates top only 500+ penetrates top and bottom __________________ Age verifier Northern Alberta Democracy is two wolves and a sheep discussing what's for dinner. Freedom is the wolves limping away while the sheep reloads. Never confuse freedom with democracy.

For the EXPERTS in fps loss

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