CA M15A4 Gearbox Broken. (Am I an idiot?)

[steve_keene]

Hey guys.

I purchased a CA AR15, which had been upgraded with a stronger spring, making it shoot around 400fps.. Now, the indoor limits around here are 300-350, so I figured "Hey, I'll just get a Velocity Reducer, and be fine!"

After reading some of the crap about Velocity Reducers, and watching a video on how to replace a spring in the CA Mechbox, and not having the 1.5mm hex key to remove my flashhider so I could USE the Velocity Reducer, I thought I'd give changing the spring a try.

(The Guy I bought the gun from included 2 springs, which he said were stock springs.)

So, after a great deal of fussing with the Mechbox, and a great deal of panicy "Oh shit I fucked it." outbursts.. I managed to get the stock (or what I thought was the stock) spring installed, and the gearbox locked up tight. I threw the motor in, and gave it a run of a few shots on auto to make sure everything was on the up and up...

and then, my "Oh Shit, I fucked it" outbursts took on new meaning, as the front of the mechbox, by the piston head, literally cracked and began to bend.

Now, my question is quite simply, would it have been the spring, or would it have been an error I made in instalation, or would it have been a combination of the two.

(As far as I can remember, it did have an aftermarket promethius aluminum piston head installed, which I've read can crack mechboxes..).

So, did I fuck up, or was it the springs fault?

ANd finally, do I have to get a specific CA M15A4 Mechbox, or can I just get any M4 style mechbox and be good?

Thanks for all your help.

-sk

[gandar]

I do believe that wasn't a stock spring. Either that or there was a flaw in your mech box.

[Greylocks]

If the gun was previously used for a long time with an over-powered spring, the mechbox metal will have weakened.
The spare springs may not be stock-power at all. Installing a stock spring is easy... so that's a clue.
Take it to an expert, this may have messed other things than just the mechbox frame. Your gear set may be screwed too.
I'd contact the person who sold it to you and ask what parts they used.

[ILLusion]

Were you dry firing it? Dry firing with an aluminum piston head on any version 2 gearbox will kill it as bad as you did.

[steve_keene]

Originally Posted by ILLusion

Were you dry firing it? Dry firing with an aluminum piston head on any version 2 gearbox will kill it as bad as you did.

Just for the 5 or 6 cycles after I put the gearbox back together to make sure it was working..

(It always seems to be suggested that you try before you reinstall the gearbox into the reciever to make sure the gearbox is working fine).

-sk

[ILLusion]

Yeah, but every shot counts when you're dry firing a v2 gearbox with an aluminum piston head. Some back pressure helps to relieve the impact. Test firing is recommended with other configurations, but never with aluminum on v2.

[steve_keene]

Originally Posted by ILLusion

Yeah, but every shot counts when you're dry firing a v2 gearbox with an aluminum piston head. Some back pressure helps to relieve the impact. Test firing is recommended with other configurations, but never with aluminum on v2.

Well.. Shit.

It's official. It's a little of Column A, and a little of Column B.

Now then, that being said, can I just drop any M4 style Gearbox in there as a replacement?

Like say, this one

Your input is appreciated.