Hw50s Grinding noise when cocking

Joined: June 21st, 2006, 3:48 am

May 24th, 2017, 1:31 am #1

Thank to everyone who provided advice on my previous post,.
I just finished doing a tune on my hw50s. The gun shoots lovely after installing the tune kit, but I'm having an issue with a grinding noise that wasn't there before (I doubt it has anything to with the kit). Here's what I did prior to reassembly.

Inspected the seal for damage
Duburred the cocking slot, piston slot, and cocking foot
Throughly degreased everything
Moly behind the piston seal, moly on the rear of the piston
Moly on the face of the top hat
Heavy tar on spring
Moly on the cocking foot/arm and plastic lever insert
Re-assembled everything

As soon as I cocked it the grinding noise was there. I fired the shot and tore it down again. Nothing out of place. I did some research and found that many people have removed the spring from the plastic cocking arm insert and did just that. I re-assembled everything, mounted a scope and started shooting. Everything was going great cocking noise was now gone, great groups and no dieseling. Then 30 something shots later the same grinding noise came back. Can anyone offer any advice? Thanks in advance.
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Joined: June 12th, 2004, 1:14 am

May 24th, 2017, 3:43 am #2

Lube under cocking slot & cocking shoe? Lube where cocking arm contacts receiver? (...Lube on back end of piston?)
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Joined: June 21st, 2006, 3:48 am

May 24th, 2017, 4:07 am #3

I think I found the problem. Will post pics in a bit. Thanks
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Joined: June 21st, 2006, 3:48 am

May 24th, 2017, 4:59 am #4

The plastic insert in the new style cocking arm is rubbing hard against the receiver. I removed the spring inside that pushes it even harder into the receiver. I went ahead and removed a bit of material on the pastic insert with sandpaper and relubed with moly. I'll put around 50 pellets through it tomorrow as it seem like the problem comes back after 30 pellets or so. Hopefully I got it right this time.

Sorry wasn't able to post pics.
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Joined: July 3rd, 2009, 1:08 am

May 24th, 2017, 6:53 am #5

Its my opinion that once the problem of the arm rubbing on the receiver is fixed that the rest of the problem is the other side of the cocking arm rubbing against that tower or even the stock bolt that goes thru that tower. I shortened the bolt a bit and polished that area and lubed that side as well and it fixed the problem. I have not figured out a way to put delrin on that side but its good enough with what I did to it. It would be great to put a delrin button on the end of the stock bolt but a lot of trouble.
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