Tumbling can smooth out the park on them. If heavily parked, they are too grippy on the rounds and cause problems. As mentioned, the Ni plated ones are gtg out of the box.No. I bought a few of the en blocs online (Garand Gear, maybe?), and others came from a karma on here. I'm going to order a couple from that guy on CMP and SLED to help me get through the occasional visit to Pembroke. Maybe over the winter I'll look into options for caring for these clips. (Most of them are the un-stamped kind...itsapissachit)
Part of improving your scores but most importantly improving the fun factor is eliminating the little frustrations that tend to crop up. Good enblocs is one of the cheapest frustration fixes to be found for Garand matches. I have a bunch of little things I have picked up from Franco, Mac, and others over the years- stuff for loads, match prep of rifles, and little things as silly as double-tying your boot laces to make sure you don't f-up because tripping on loose laces. Since I drive 1.5 hours to these things, I don't want to screw up a match over something easily preventable.