I agree with what Kingfisher said about the forward stock screw. If it's a little too long the cocking lever could drag on it and give you that galling feeling.
As for it not cocking, that may be due to the rear trigger guard screw being too tight. Might try backing that screw out about an 1/8 to a 1/4 turn and see what happens.
Ok, if it's not the lever dragging on the screw and it's galling on the tube, but only when the action is in the stock, you might check the inletting of the stock and see if there's any rub marks from the cocking lever. Could be a clearance issue with the stock that's pushing the lever up into the action.
Fixing the tube/cocking lever galling is pretty easy. JM sells a plastic insert that you can cut down and fit in the lever to keep it from rubbing on the tube. Or you can make your own insert from a plastic jug.
Here's a link that shows the JM insert I put in my HW30S. It should give you an idea how to fit one in yours, whether it's JM's or a homemade one. Main thing is you want the insert to sit just above the top edge (but not too high) of the lever to keep it from rubbing on the tube.
https://www.tapatalk.com/groups/TheDianawerkCollective/the-hw30s-i-m-likin-it-a-bit-long-t13141.html
Glad you got it sorted out. But I don't understand why you had to remove so much metal from the cocking lever. Most of the time all that's needed is just a smoothing up and polishing of the lever so that if it should rub on the tube it will just slide against it instead of eating it away. On my 30S I didn't even do that. All I did was add the JM insert and put it back together. No problems with any galling since.
Anyway, I'm glad you got it fixed and now you can enjoy your 30S.
i decided to check deeper because everytime i thought it was fixed it would start back galling after ten or fifteen shots so i pulled it apart and the galling was the piston at the back where it is belled out , it was galled half way around so i put it in the lathe turned 5 thousandths off polished to 600 grit and now after fifty shots its smooth as silk has anyone had this problem before?
Was there any lube inside it? That was, and may still be, a problem with the Diana break barrels as they generally came lacking proper lubrication from the factory. But I don't think I've heard of this in an HW.
I just shot mine yesterday and it still feels nice and smooth. I've had it for almost 3½ years and haven't been inside it yet. Only thing I've had to do to it is add the insert to the cocking lever.
i didnt go to the trouble to button my piston i probably should have but it is shooting very smooth and acurate now if i start feeling it galling again i will put the piston in the mill and button it but so far so good just removing about 5 thousandths fron the bell on the piston seems to habe taken care of the problem we will see