gearbox suggestion

[freewheelin4eva]

just wondering what ya'll would suggets for a new ver2 gear box, what size of bearings, and what brand, not going to crazy hoping to get 320 fps.

[Greylocks]

Normal oilless bushings, spring guide, and something like an M100 spring or equivalent. The standard parts for the rest.

[TokyoSeven]

Some decent metal bushings to replace the stock ones and a good M100 or equivalent sounds about right, you could cheap out and use the stock spring guide, but I wouldnt.

Bushings come in 6mm and 7mm what size is dependant on what your gear box takes.
I recommend systema brand for both bushing and spring.

[Greylocks]

It would also help a lot if you told us for which gun, by which company... I should clarify what I meant: New bushings, new (better) spring guide, new spring. The rest can stay the same.

PS, knowing how to put it all together is no easy task the first time; go meet a gun doctor and watch.

[freewheelin4eva]

sorry hear is a little more info, it is an TM M4, got it broken as a project, had been upgraded w/t metal bushings, shimmed, spring guide, high torque gears, and a systema M120 spring, all into a TM gear box. I am sure every one can picture what happened after so I was told by original owner, maybe 1 or 2 thousand shots, the front of the gbox blew apart, and the tm hopup blew apart as well.
so I got the gun for a reasonable price, plan to put a gbox in it and maybe sell it.
so me being somewhat uneducated compared to some of you guys, would like to know what gbox is good and will hold up, also I think I will go w/t bearings, from what I do every day, I know that bearings are better than a bushing also bigger the better, well more load and stress they can handle. I take it It is the same in a gbox. am I right? and as I posted before I am only going to make it shoot 320 max.
oh and this will be my second gbox rebuild, the first one is still shooting strong after bout 10 thousand through it.

[TokyoSeven]

The thing about mechboxs with or without upgrades is that its not whether or not they will far apart, its about when. Upgraded parts maybe of higher quality and can take a longer punishment, however they are not invincible and just take longer to wear down then stock parts.

An m120 with metal bushings and only upgraded springs is pushing the limits of a stock v2. I suppose if all those parts are still in order, just grab a new mechbox, rehouse them, put your new spring in, and some stock gears and new hopup and you may be good.

[ILLusion]

At 320fps, you can get by with a bone stock gearbox, and at that velocity, even 6mm bearings can handle the load with the added benefits.

The front end doesn't just "blow apart." It usually happens with a combination of:
- Too strong of a spring
- Too stiff of a piston head (such as an aluminum one)
- Too much dry-firing.

If you want the gearbox to last a looooong time, throw in a silent head set with that.

[TokyoSeven]

Aluminum? Uh oh! *questions the newly purchased systema aluminum piston head on the counter*

I knew I should have gone with the other one. Oh well the whole cylinder piston system is getting replaced, it should be fine.

[freewheelin4eva]

ya this gun had a systema aluminum piston , and aluminum piston head.

I also noticed that when I was taking the gun apart I noticed that the thrust bearing on the inside of the piston did not rotate freely what so ever, oh and also the gun must have lastly fired on full auto and not fired on semi last, since the piston was pulled half way back, just a few things I have noticed.
cleaned all the gears up which are systema High torque gears, and they are all good, the pinion gear shows a little wear though.

[Darklen]

Originally Posted by freewheelin4eva

...and a systema M120 spring, all into a TM gear box.

= very bad idea.

A Systema M120 spring would put an M4 into the 380-400fps range, waaaaaay over what a stock TM shell can handle, especially with a metal piston & cylinder head set. I've replaced about half a dozen gearbox shells for tha same reason, too much spring, not enough reinforcement.

To get 320fps is easy, even with a stock TM spring. First off, get a tight bore barrel, 6.04mm or 6.03mm. Biggest bang for your buck. Gives you speed, range and accuracy increases in one upgrade by forcing the same volume of air to go through a smaller tube. Next, a good quality ball bearing spring guide and piston head. These free up energy from the spring by eliminating binding. Then seal up the cylinder, cylinder head and hopup chamber as much as possible. I've have very good luck with a combination of a Systema silent head set (piston & cylinder head) and a Systema hopup chamber with a Guarder hopup sleeve & bucking. Going with a bore up set (which increases the internal volume of the cylinder) will give a modest performance increase as well, but you have to relace the cylinder, piston head and cylinder head as a set for it to work.

[S.H.I.E.L.D.]

Never hurts to go to a reinforced mechbox either. A ProGear or other decent brand to take increased stress. Colder weather with a "hot" gun in a stock mechbox case can cause your mechbox to crack in some instances. Nothing is infallible though. Cdn_Stalker is a good guy to talk to, same with Madmax, Illusion and some of the old boys who've seen inside of mechboxes more than anyone. Make sure you get the right combo of gears, piston etc. to get the longest life you can out of your gun. And if you aren't comfortable doing upgrades yourself, listen to Grey and get a gun doc to look at it.