M14 Airleak 118fps

[The Dr]

Hi All

Hopefully someone can help me.
I have a TM M14 which I had to change the hop rubber on as the original had started to perish.
I cut a FireFly rubber to fit and when it was next chronod it was firing at 118fps....
I've taken it apart and everything seems right.

Anyone have any ideas?
Cheers

[rjdo]

Re: M14 Airleak 118fps

What was it firing at before you decided to change the rubber?

Could you have mashed the rubber in when setting the barrel back in the hop up? Have a look in the back of the hop up with the barrel set in it, you might have been a bit too forceful and the lips of the rubber might not be getting a decent seal.

Have you messed with another internals (e.g. Had the gearbox open for cleaning etc) recently?

NB. This is based on my personal experiences fiddling with my TM G3, rather than an M14. I'm also no expert, rather I tinker, mess it up, then fix it through trial and error.

[The Dr]

Re: M14 Airleak 118fps

It seemed OK before but i honestly can't remember.
I checked the rubber and it was in there fine, reckon i could of cut it too short so that it doesnt created a good seal?

I haven't touched any other parts, just the barrel and hop rubber.

I did test it with it under powered and changing the rubber has fixed my first issue of it curving.

Cheers for your help.

[rjdo]

Re: M14 Airleak 118fps

So you were having those wonderful stray rounds curving off beforehand and changing the rubber has fixed that? That's a win in some respects then.

Like I said before, I'm more of a tinkerer but I've never come across poor airseals from badly fitted hopup rubbers causing that much of an fps drop. Someone else might know/have experienced such a problem though.

I'd hazard a guess at air leaks/poor seals on the inside of the gearbox, but I'd also want a second opinion before going and delving around in one to sort it.

[The Dr]

Re: M14 Airleak 118fps

Ok well thanks for your opinion. I'll see how it goes Sunday and if not I'll have to enter the gearbox which I really don't want to do.
I am more of a bolt action guy, much simpler haha
Thanks again!

[helpimonfire]

Re: M14 Airleak 118fps

Try wrapping some PTFE tape around the hop unit at the barrel end of it. Try to seal the gap between the hop unit and barrel. Might help a little until the rubber has bedded in. I've done this before, not entirely successful but helped a bit.

[Figjam]

Re: M14 Airleak 118fps

That much FPS is also possibly the nozzle not aligning properly with the hop rubber lips. I'm not familiar with the M14, but is there a spring to push the hop unit back against the gearbox like in an M4? Or the rubber is not seated 100% right. Often you can fix this by just taking it off and trying again rather than getting all technical.
As said elsewhere, if it was shooting well before the mod and all the work you've done is with the hop unit its highly unlikely to be anywhere other than with the hop unit, so its either this or give it a bit of teflon tape.

[The Dr]

Re: M14 Airleak 118fps

Cheers for all the help

I just took it apart and put it back together again then chronod it. Now it's at 180, someone suggested trying a new spring.
What size spring would I be looking at?
Btw yes it does have a spring pushing it back towards the nozzle.
Oh and the hop rubber isn't new it's my old one from my L96 so doesn't need bedding in.

Cheers again

[The Dr]

Re: M14 Airleak 118fps

Took the gear box apart today to put the new spring in to find out the old one was snapped in half.
Problem solved.
Now to just get it back together (2 hours so far) haha
Cheers again