M4 Partialy FUBAR'd?

[Malakai]

My dad's M4 has suddenly lost power after a barrel swap (to a Madbull 6.03). He's had the entire rifle stripped and checked several times, and no change. The rifle has just lost juice, and shots are landing around 15-20ft. He's swapping the barrel back to stock as I write this, will post the results soon. But in the mean time, does anybody have any ideas to what could be causing a MAJOR loss of FPS and range? A checklist of stuff to go through would be appreciated. Cheers in advance.

[Phatvortex]

Re: M4 Partialy FUBAR'd?

When you changed the barrel, you put the hop rubber back on right?

Also check that you put the nub back in. Tiny little tube of rubber that sits under the hop arm.

[Malakai]

Re: M4 Partialy FUBAR'd?

Yup. Everything was installed properly. He just put the old stock barrel on and gave it some test shots before it was completely assembled, and it was firing how it should have been. After completely assembling the rifle, its back to shots dropping at 15-20ft. He thinks there's an air leak with the piston O-ring or something.

[Phatvortex]

Re: M4 Partialy FUBAR'd?

Is the hop unit fully engaged with the gearbox?

[Phatvortex]

Re: M4 Partialy FUBAR'd?

Only reason I say it, is because it was firing fine when it wasn't all together. There is a lip on the hop unit that goes into the gearbox, make sure its in, and give the hop unit spring a little stretch to keep it there.

[I'mhitalready]

Re: M4 Partialy FUBAR'd?

You could have torn the hop rubber by removing the barrel, this would cause a massive air leak and drop in power

[mrpugster]

Re: M4 Partialy FUBAR'd?

Are the barrels the same length?

[CK]

Re: M4 Partialy FUBAR'd?

Why would barrel length matter? Only thing that would prove a problem there would be the cylinder needing changing as well, would need to be a dramatic length change.

It sounds like a hop issue. perhaps seated incorrectly.

[mrpugster]

Re: M4 Partialy FUBAR'd?

Why would barrel length matter? Only thing that would prove a problem there would be the cylinder needing changing as well.

Without asking the question you never know!!!

[Phatvortex]

Re: M4 Partialy FUBAR'd?

Why would barrel length matter? Only thing that would prove a problem there would be the cylinder needing changing as well, would need to be a dramatic length change.

It sounds like a hop issue. perhaps seated incorrectly.

Remember, there's no such thing as a stupid question. Only a stupid person.

It does upset me how many tech threads have people suggesting things that have no relation to the issue the OP is having.

[Malakai]

Re: M4 Partialy FUBAR'd?

and give the hop unit spring a little stretch to keep it there.

I've just spoke to him and he says the spring might be bent a little. Gave him a spare, we'll see how that turns out.
And just for the record. both barrels are 362mm in length. One is the stock barrel, the other is a Madbull 6.03.