Problems/Questions Upgrading M733 To 400 Fps

[GlockFu]

I've got an M733 that I'm having a hard time getting to 400 fps. All I have in it so far is metal bushings, M120 spring, KM tightbore and Systema Duracon Piston Head with bearings. It is only registering at an average of 362 fps with .20 bbs

I've talked to a lot of people and have done a lot of research and one of the things that I think will help is changing my cylinder from the stock closed cylinder (don't know why TM put these in there) to an M4 cylinder. That's the only problem I can find but I really doubt it will jump the fps to 390s.

My friend has the exact same gun (we ordered it together) and he was having the same problem. He finally got it to average 397fps but he is using metal bushings with dual oil chambers, same piston head as me and a SP120 spring. Before he changed the closed cylinder to an M4 cylinder it got 385 fps, thats why I don't think my gun will jump to 390's with the cylinder change.

I was thinking about chaging out my spring to an SP120 as well but after doing research I think that spring is too strong for my internals. Also, when he shoots semi auto it sounds like his motor is straining a lot more then mine. So I thought, why don't I just switch out some of my other compression parts instead to get more fps and so my gun doesn't have to take as much abuse.

These are the parts I was thinking about getting. Any suggestions of which ones to get and which ones arent worth the money would be cool...
1) Systema cylinder $10 (I already have a CA one someone gave me tho)
2) Systema Nozzle $8.50
3) Systema Spring Guide with Bearings $15.50
4) I was thinking about getting a new Cylinder Head but I'm not exactly sure what that would do

Sorry that was so long but I have a couple more questions...
1) Why the hell isn't my gun shooting 390's with what it has??
2) Is the SP120 too strong without upgrading my other internals (gears, piston, ect...)
3) What parts would you suggest to increase my fps to close to 400 fps

THANKS FOR ANY HELP!!

sounds like you have air seal problems...for all reasons, you should be OVER 400fps.

but, since its an old gun, the cylinder head oring may be dried out. Lube it, lube it like crazy. thats one way to find out if its a air seal problem. I had the problem with my AK. had all the parts and was getting really low FPS. i dumped all kinds of lube in the cylinder...i mean lots. and didnt fire it before the chrony. all the extra lube isnt a solution, but if its an air seal problem, your 1st shot with the extra lube should tell you what the problem is.
with my AK, i was almost 200fps lower then what i should have been...and i couldnt figure it out. so i lubed it like mad and fired it through the chrony...my 1st shot was back up to where it should be...that told me that it should be one of the fallowing:
cylinder head
piston head
cylinder
nozzel
but thats just something i tired, and its messy.

also, check your hopup, lube it....also make sure the barrel is in the right position...once while installing my tightbore in my SR16, the spring on the hopup fell off during install and i was getting low fps because the barrel was to far up from the mechbox.

[CDN_Stalker]

Barrel is too short.

[GlockFu]

I'm pretty sure everything is in place. I had AEX look at my gun and another guy that works on airsoft guns. We did the compression check by blocking the nozzle and pushing the piston in and it seemed good. I know this doesnt always say everything but it seemed okay.

I am pretty sure that I am going to get a new cylinder, cylinder head and piston and then see what happens. Do u think a new nozzle will do anything to increase my fps?

I dont think the barrel is too short. Yes it is shorter but I have heard of people getting thier m733's up to 400 fps.

the barrel length shounld make much difference

[Mantelope]

It's definitely the cylinder.

[CDN_Stalker]

Was talking to Illusion today, is why I bought it up, because according to him even a 10cm barrel length difference can make a huge difference on fps. I put a 110 spring in my MP5, had the bearing spring guide in there, calc'd rough fps out to be about 375fps, was getting at the top end 345fps (my Glock 19 shoots at 340fps, AEG should be higher). Hence my saying, he's seen 110 springs put out everywhere from 330fps to 400fps, depending on other upgrades and barrel length. Seeing as how this topic is about a 120 spring................

[damage]

Inner barrel and cylinder should match.

[Greylocks]

Agreed, there is only so much you can do with a very short barreled gun.
Go for dependability and accuracy instead. 400fps is not the holy grail, it's an upper safety limit, not a goal to reach.
Nothing wrong with 360fps if the gun works well.

[Skruface]

High FPS does not necessarily mean a "better shooting" gun. I've built a number of 340-350 FPS guns that regularly outshoot (groupings) and outrange (effectively - not lobbing bb's) 400 FPS guns around here.

I also own a 350 FPS M733. Since it's already a short gun, there are a number of tricks you can use to increase the barrel length, like buying a 200mm silencer and installing an G3-length tightbore, or a 250mm silencer and an M16/SIG550-length tightbore. You will need to swap out the cylinder for a more appropriate one if you do this.

Also, a KM "New"-style hopup bucking will make a difference. So will cleaning your barrel every time you walk off the field.

You can also wrap some hockey tape around the inner barrel so it fits very snugly inside the outer barrel.

Finally, as a last resort, I'd try a new cylinder-cylinder head-nozzle combo. Make sure the nozzle is the type that has a rubber o-ring on the inside.

[damage]

I have one too a Full metal M733 with maxed out internals and it shoots 383fps on Prometheus MS110sp.

[GlockFu]

Originally Posted by Skruface

High FPS does not necessarily mean a "better shooting" gun. I've built a number of 340-350 FPS guns that regularly outshoot (groupings) and outrange (effectively - not lobbing bb's) 400 FPS guns around here.

I also own a 350 FPS M733. Since it's already a short gun, there are a number of tricks you can use to increase the barrel length, like buying a 200mm silencer and installing an G3-length tightbore, or a 250mm silencer and an M16/SIG550-length tightbore. You will need to swap out the cylinder for a more appropriate one if you do this.

Also, a KM "New"-style hopup bucking will make a difference. So will cleaning your barrel every time you walk off the field.

You can also wrap some hockey tape around the inner barrel so it fits very snugly inside the outer barrel.

Finally, as a last resort, I'd try a new cylinder-cylinder head-nozzle combo. Make sure the nozzle is the type that has a rubber o-ring on the inside.

How have you gotten more range then a 400 fps gun with a 350 fps gun? My main concern is not really the fps itself but more of range. I figured that the faster the bb was coming out of my barell the farther it would go. My whole reason for upgrading my gun was for range. Can you please explain how I can get more range without increasing my fps?

[CDN_Stalker]

I've picked guys off at 150ft with my 365fps MP5, using 0.25g BBs (for a 229m inner barrel, that's pretty damn good, mind you, I know how to best shoot all my guns, GBBs with heavy sniper BBs going out past 120ft to sniper rifles with match grade ammo hitting guys 230ft away). Mind you, I aimed a couple feet above their heads, and things have generally been easy to reproduce. Hop up setting and BB weight is more important than higher fps. I use the Guarder clear (50%) hop up rubber in all my guns, those are amazing.

[damage]

Originally Posted by GlockFu

How have you gotten more range then a 400 fps gun with a 350 fps gun? My main concern is not really the fps itself but more of range. I figured that the faster the bb was coming out of my barell the farther it would go. My whole reason for upgrading my gun was for range. Can you please explain how I can get more range without increasing my fps?

Longer inner barrel is your answer.

[GlockFu]

Originally Posted by damage

Longer inner barrel is your answer.

I was hoping to stay away from that since that was the main reason I got the m733... is this the only way?