I am guessing about nickel silver on the 18, there may be a problem with soldering it to the tube where the brass there is no problem with the process.
I hope Scott might see this and clear up this fake news
Peter
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Peter Kaufman NRA Life GOA SAF RKCC CM-023 RKS #5642 SHAG # 005 Ironwood Nut Life is too short to have ugly knives