What about RWS Hobby's? The lighter weight might also boost the MV a little.https://www.airgundepot.com/rws-hobby-22.html#231-7377
I checked the two wadcutters I use and both would work for you. They are Daisy and Webley Vermin Pell. The problem is both have been discontinued. I think you can get the Webley pellets overseas but they won't be cheap. Check eBay. Good luck
Might be looking at the other end...seems like a thicker skirt edge would work to stop that kind of nesting. Can't think of a current .22 WC that doesn't have at least a little edge bevel.Don't have a 600....did have the same issues with a "side shuttle" Crosman 99. Are people here that are still running their 600's, so there must be at least some pellets that work.
This is a tin of current production Hobby 22s. I can't force the nose of one inside the skirt of another one without it sliding off at an angle. It took several attempts to get one to stand on top of another one without falling off.
In my C600's the RWS Meisters "seem" more accurate than the RWS Hobbys, but both feed very well. -------While Mac1 claims the JSB wadcutter works well in C600's, they didn't in mine (at all).http://www.mac1airgunshop.com/jsb-exact-express-22-14-3-500-tin-p/jsb13.73.22ma.htm?CartID=1But in my SW78G, this JSB pellet is wonderfully accurate. The problem is that I have one tin left and don't want to open it yet. -------Pyramyd Air shows to have H&N wadcutters soon. I haven't tried them since I've acquired my C600's. https://www.pyramydair.com/product/h-n-sport-22-cal-13-73-grains-wadcutter-250ct?p=1505
I think you need these, and they are available from many vendors on Ebay Almost forgot the link 500 pellets starting bid $14.00 ...https://www.ebay.com/itm/274820110937
What about wide hollow points, such as the Crow Magnum?https://www.pyramydair.com/product/h-n-crow-magnum-22-cal-18-21-grains-hollowpoint-200ct?p=732Would round ball work (assuming it is large enough in diameter to grip rifling)?https://www.pyramydair.com/product/gamo-round-22-cal-15-43-grains-lead-balls-250ct?p=610