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Horrible 'Rattling' Noise When Shooting (+ Couple Questions).

4411 Views 15 Replies 4 Participants Last post by  souponherhed
I've just upgraded my L96 with the following:
PDI Hop Chamber
PDI 6.05x495mm Barrel
Laylax Zero Trigger
Laylax 3 Element Piston
Laylax Spring Guide
Laylax Piston Head (accuracy cup thingy)
Laylax Teflon Cylinder
Laylax Cylinder Head
Laylax 170sp Spring

It's shooting quite hot now though - 590 on .2s, so I need to lose 90 FPS.
590 on .2s = 417 on .4s, both make a horrible rattle noise as I shoot. What could it be? Or is it simply the high velocity?
It used to do it with .2s when I was shooting 500 FPS, but not with .4s (travelling at 360 FPS).

Another problem I'm having is the cylinder scraping on the inside of the outer barrel as I push the bolt forwards. I've lubricated it, but it's not made a difference. The outer barrel is a PDI Fluted one if that helps.

I also, had problem with a Prommy hard rubber. The lip (where BBs enter, that stops it going all the way over the barrel) is really tough and BBs get jammed on it, making it extremely hard to push the bolt forwards, and when I do, the BBs are completely ruined, and now the hop rubber's in pretty bad shape. Any idea on this? It was definitely on right.

And finally, apart from getting a new spring, what's the best way to lower FPS? If cutting the spring, I know one coil at a time, but do I have to sand it down or smooth it off? And which way round does it go, cut end in the piston, or cut end on the spring guide?

Sorry for rambling a bit, but I kinda need this rifle shooting perfectly for two weeks time as I have a weekender and want some nice hits :).

Thanks a lot,
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Yup ranger nailed it on the scrapping. If you are missing that little ring, try and find one of those old plastic film canisters. You can cut the bottom off, and cut down the side. With a little fitting you can get the canister to fit and you have a nice little sleeve :D

For the spring, yes go very slow as one wrong cut and you are out a spring. And yes you should file and sand the end down. This will make sure that it doesn't grab on to anything on the inside of the cylinder, and none of the scrapings get into your bucking or barrel.

As for the rattling it could just be the tension of the spring releasing. Springs of that high of an FPS rating are already under tension when you close the cylinder up. And when the sear lets go of the piston all that energy in the spring is released and snapped forward very quick. When the spring hits the end of the space, it will still have momentum, and will thrash around inside of the cylinder. And that is probably what you are hearing after you fire the shot.

It is really nothing to worry about, but just watch the stress on the cylinder head. You may end up finding that the cylinder head will start to pull out of the cylinder itself. So I would look at the cylinder after every game just to make sure that there are no signs of wear or anything like that.
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What about that small set screw that holds the outer barrel to the receiver? If you over tighten this it will poke through and scrape the cylinder ;)
Hmmmmm..... what about any burrs or anything like that on the inside of the barrel? Take a cotton swab and run it inside the barrel, as well as the receiver. If you see any of the cotton fibers stuck on the inside of either part, then you will have to sand those down and make it smooth.

I know a few of the rifles I have had, did have some really nasty ridges and stuff on the inside of the receiver. After some time on the lathe you can get it nice and sanded down and smooth.
It could just be the sear that is riding on the cylinder itself as well. Or one of the screws that is holding the trigger mech on is a little to long.
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