Generally I've been impressed by what folks have posted about the accuracy of their Knight rifles on other forums.
I suppose watching company videos showing extreme long range accuracy from their Green Mountain barrels also persuaded me, but I had already seen similar proof about other Knight models.
But whether to buy one depends on what kind of gun appeals to you and its price range.
Even the least expensive Knight rifles are very accurate.
There appears to be a bare primer breech plug and bolt body adaptor for those who don't want to use full plastic jackets.
The adaptor is preferred by some for use with BH 209.
I believe that they are sold by Lehigh Defense through its SSK Industries subsidiary. --->>>
https://www.lehighdefense.com/firearm-components
This thread has very favorable comments about the Mountaineer showing that some folks are very satisfied and wouldn't trade theirs for any other gun. --->>>
https://www.modernmuzzleloader.com/threads/knight-mountaineer.37349/#post-326426
I found that thread by doing an advanced search for Mountaineer on the modernmuzzler forum.
Here's the raw search results if you want to explore them further: --->>>
https://www.modernmuzzleloader.com/search/193555/?q=mountaineer&o=relevance