If you have GOOD compression on your gun.. please read this.
 

i need some help. can anyone suggest me a good combo of cylinder, cylinder head, nozzle, etc... that will work nice together to fix my compression. i have a TM m733 commando with the following:
promethius ak47 length titebore
guarder steel bushings with dual oil chambers
systema duracon pistonhead
guarder sp120 spring

from what i hear..im suppose to be shooting in the 420'sfps. im only shooting 398fps. so im guessing my problem is bad compression. if you guys can either just tell me the combo you have on your guns or just recomend me which things to get that to hopefully fix my compression. oh one more thing...i read somewhere there is two types of grease to use...one for the gears and one for the cylinder. i already have the lithium grease.

You aren't far enough off to be worried about compression. I'd say the only thing missing is the bearing spring guide which would add another 15-20fps to your velocity (compresses the spring a bit more, gets a little bit more oomph out of it). Whatever guide you read to assume 420fps, chances are it was upgraded, and you didn't mention stock or bearing spring guide.

BTW, if you have a leaking problem somewhere, you'd most likely lose a LOT more fps than a mere ~20fps. More likely 100fps loss at least.

And the white lithium grease you have you can use for both the gears and the cylinder.

Ewww!!! Turf that lithium out of the cylinder. Use a silicone-based grease. It can be had from Marui, Systema, CA pretty easily. Lithium is one of the main causes of G&G failures and IMHO the primary cause of CA M249 piston failures. Marui doesn't use it in the cylinder and for good reason.

Lithium offers too much resistance to piston movement as it is much "stickier" than silicone grease. Over time, lithium will pick up contaminants and turn into a black sludge. No good can come form it's use in the cylinder. Gears is a different story. It work fine on gears as it adheres well to everything.

hmm ok ill try silicone grease.

fyi i use schwinn bicycle grease and it makes my m4 sing. it can be had at any crappy tire and is dirt cheap.

do you use that on the gears or cylinder?? and by what means do u mean ..makes ur m4 sing hahah

Superlube on everything!

Word is common that too much hop up setting is the main cause of CA M249 pistons shredding, based upon experience of course. G&G............ well, that seems to be the main cause of failure right there, not what grease is used.

I agree that white lithium grease can end up being a bit too sticky for some uses, but it's an option that is better than nothing at all. Recently I've switched to anhydrous graphite which is working amazingly well in my guns, better than anything I've tried yet.

The CA M249's that I've replaced the pistons in were chewed to hell in a specific way. Not 1 or 2 teeth, but more like 7 or 8. The only guns other than that I've had to fix with that same destruction were G&G. Not only UMG, but M14 and GR16 series. All used lithium in the cylinder.

Systema, Marui, G&P, ICS, and other CA guns I've worked on did not use lithium in the cylinder and I have never seen another piston failure like that in any of their guns.

Too much hop-up destroying a piston? I'd like someone to explain that one to me.

Frankly, you're better off with no lube than with lithium. I've seen guns go for thousands of rounds bone-dry and others with lithium pack it before the first mag is empty. Even silicone oil in the cylinder is very effective if you have nothing else.

But you've had your experiences Stalker and I've had mine. We both go with what we know.

I recall someone saying the CA249's hopup could be overcranked and actually block BBs and cause a jam, resulting in tappet plate dammage, piston and gear dammage.

I see, but the piston would end up being random collateral damage, much like the other damaged parts in the mechbox, and not unlike the damage that could occur with any other mechbox when the tappet breaks.

The damage that I've seen is the piston chewed to rat-shit, but not other damage to any other parts.

One of our guys bought one of the first CA M249s in Canada when Kang got them in. Within a thousand rounds or so, his piston got chewed to hell (mind you, was a CA stock yellow piston). We installed another one, stock TM piston we had around, it did the same thing. He contacted Kang about it, who contacted CA, was informed that adjusting the hop up too much (as in enough to fly 0.25g like any other gun) was what caused the piston to chew. We got in a shipment of newer (aka. version-wise) CA M249s and I don't believe any of them have had any piston problems, mainly I'd assume, because everyone of the new owners were told not to set the hop up too high, just a touch.

I agree though, this is my experience and the info as I know it, and is pointless for us to niggle right & wrong. The later batches of the M249s have been improved upon over the initial batch.

so wait, the gun is firing legal limit for MOST feilds and you want it higher?

Check out his location.