I don't even use a lock ring to hold the sprocket, I think they are more dangerous than they're worth. I'd rather have the rear sprocket unthread on a descent than to have the chain get trapped and have the rear wheel lock up because the sprocket won't unthread. I raced track for 35 years and never used a lock ring and never had any problems. As long as you tighten the sprocket with a chain tool, it will stay on as long as you don't do a stupid skid stop. Not using a lock ring lets you use the older threaded road hubs.