Not having any experience with AR builds, or ARs in general, other than shooting a couple, I can't answer your question. I will say (please don't take this personally, as I'm saying this for the benefit of others who may have similar questions) that this is a question that should be asked before a purchase, not after. Having said that, I'm sure some people here can speak to the quality of the Mag tactical lower.
I don't think there's such a thing as a "bad" AR lower anymore. Making a lower is pretty common, enough so that it wouod be hard to get it wrong. The only variable is the size of your buffer tube if you should want to change later. If the LPK fits and functions go ahead and build it. I wish I could find a reasonable set of anything to build lately.
CMMG makes great quality lowers, and I own several CMMG firearms. As for bad quality lowers I have yet to experience a bad one. Though I always dismantle complete lowers I receive, and replace it with my lowers.
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