i recently noticed my 350 shooting low for no reason/after inspecting it i noticed the lock mechinisim on thetube is wore form the ball bearing rides on it whn cocking.
and so when the gun fires is causes the barrel to move dropping slightly when fired
can the little piece on the tube side be replaced?

Yes its a part that Umarex can get you !

ahh thnxs will have to go to there site and order one

do you have through your 350 if I may ask? I remember the little locking mechanism that comes in contact with the ball was like new in my 350 after ~2,500 shots. Did you try cleaning the barrel or put the gun through the chrony to check velocities? It's possible the performance is not there? Just guessing, but please post back with your findings after your replace that part.
thanks
Harry

RWS Diana 350 .22 (MIA w/Curtis)
RWS Diana 36 .177
RWS Hammerli 850 .22
Lemak custom AF Condor .25
Talon Tunes AF Condor .25
Airhog tuned AF Condor .22
Crosman custom 2300XT .22
Various other Crosman Pump & CO2 .177

the gun has about 3000+ shots through it ran it over the chrony an got 860 fps with cp 14.3 gr. i never had a problem with the gun in till a weel oor so a go when the POI keep dropping about 3 inches every few shots at same veloicty . i checkd the gun out and found the little latch that depresses the ball deten had worn quite a bit i guess the ball bearning was stickng more that it should and caused wear. but gonna order the part soon hopfully it wll corect the problem any idea on how the latch peice comes out on the schem on the web site looks like its threaded in but not usre is its loctite in any idead please let me know