I got a couple of nipples to try out. The first thing I found was the nipple hole is .026 vs .034 for a Hot Shot. I had a ton of hang fires. Then the deal breaker. I tightened the nipple in and went and shot. The gun shot well and no hang fire. I get home and I can't get the nipple out. So I work on it and finally get it out. I found that the threads are longer than a hot shot. What difference does that make?
Well the longer threads went down and hit the clean out screw. Once it hit the clean out screw the threads were messed up and as I backed out the nipple it goofed up the threads a little on the breech plug and the end of the nipple is really messed up. I can't get it to thread back in.
So I threaded in a Hot Shot and it went in tough but went in. I backed it out and back in a coulpe times. I think it will be fine. The Platinum nipple is maybe hosed. My plan is to get a 1/4-28 die and try to thread it on. Then shorten the nipple a little. Heck it is hosed so I might as well Frankenstein it.

The end of this story is if you have a Green Mountain barrel I would highly suggest to NOT buy these nipples.

Good advise. Thanks for the heads up.

Thanks Ron.