Rifle grinding when cocked

[No.1Dad]

To start off I'd like to thank the members of this forum for helping me out with any of the problems I have encountered thus far. I greatly appreciate you for going out of your way to offer advice.

I was pumping lead into the ground trying to get to that magical 500 number to break in my rifle. And about 80 pellets in I started to hear a light grinding/scraping sound. I stopped when it continued 5 shots after.

Could it be something as simple as needing a little bit of oil? Or is the gun going to get serverely damaged if it is used any further?

[oldpro]

 What make and model please

[Kailua]

If its a metal scraping sound.  I don't think oil will help.  Is it a springer?

[Motorhead]

Sadly ... most mechanical grinding upon cocking spring guns is a BROKEN SPRING gouging into sides of tube. 
EXTREME lack of lube may as well, tho less frequent or noticeable for most users.

[No.1Dad]

What make and model please

It is a Benjamin Titan NP. If you need the model number I can provide that after work.

[No.1Dad]

If its a metal scraping sound.  I don't think oil will help.  Is it a springer?

No, it is a nitro piston

[avator]

Had this happen to a Crosman Nitro Venom. Pretty sure it's the same power plant setup basically. The piston was canted and rubbing metal to metal on the compression chamber wall. I ended up doing the old school piston buttons. The way I did it was to clean the piston with alcohol. Then I used super glue to attached 4 1/4 x 1/4 inch nibs of plastic soda bottle at 2:00,4:00, 8:00 and 10:00 around the butt end with the contact point being at 12:00. Then I sanded them down until it fit nicely back into the compression chamber. You will want to de-burr all the stamped out slots and holes and smooth out and scarring from the grinding. Apply a light coating of moly paste and put it back together. It's a good time to do all the other springer tune mods such as, brass pivot washers and polish/lube the trigger parts. Possibly even upgrading to a CDT trigger. This worked very good for over a year and several shots before the nibs wore out and the grinding returned. I've since traded the gun off to Longhunter and I think he has come up with a more permanent fix. You might PM him and ask what he did. If it's under warranty I would look into a replacement first. Being a Nitro piston gun, there is not going to be a spring in the gun to be the cause of the issue.

[avator]

Also, there are other possible causes such as foreign object is there and there are also other ways to button a piston such as drilling pockets in the piston and filling them with JB Weld. All depends on your abilities and access to tools. I'm sure others will have more suggestions. I now have a Crosman Blaze NP and, so far, no grinding.
Good Luck

[anuthabubba]

Sounds like Bill could be right. Once fixed an R9, for a guy, that the upper piston skirt had galled the main tube due to lack of lube, making a horrible grinding sound when cocking. After smoothing the galled area, OS buttoning and thoroughly moly lubing the tube/skirt, it shot fine w/o the noise. I'd suggest not shooting it 'til it's fixed.

[No.1Dad]

Also, there are other possible causes such as foreign object is there and there are also other ways to button a piston such as drilling pockets in the piston and filling them with JB Weld. All depends on your abilities and access to tools. I'm sure others will have more suggestions. I now have a Crosman Blaze NP and, so far, no grinding.
Good Luck

Thank you for the advice. It is still under warranty so I am deciding whether I should send it to crosman for repair/replacement or contact a forum member to repair and tune it.

I have next to no experience tinkering with air rifles so I'm leaning more towards having it tuned by someone. Is there anyone here who specializes in this sort of thing?

[mobilehomer]

My NVD was doing the same thing. it was the foot of the cocking arm rubbing against the inside of the slot. I took it apart, de-burred and moly lubed the compression tube and the foot. No more grinding.

[anuthabubba]

Could be that.