Let's be honest about it

So in this case [the letters of Ignatius] one is actually dealing with eleventh-century manuscripts witnessing to a second-century writing which often loosely cites the text of the NT in the (vain?) hope of trying to glean insights into the state of the text of various NT writings prior to, or contemporary with, the earliest hard evidence of actual texts of these writings. From the outset the potential of this approach to yield decisive results should be judged for what it really is—extremely limited. Rather, at best, the quotations in these writings, if cited accurately rather than loosely, if transmitted faithfully rather than freely, if randomly preserving units of text that are known to preserve variation units that allow a differentiation between text forms, may then at best provide corroborative evidence to supplement observations about the state of the text in the second century. The probability that anything decisive may be adduced is incredibly low.—The Early Text of the New Testament, page 283

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It makes looking for the proverbial needle in the haystack seem easy! Interesting book, by the way. It certainly doesn't lend itself to excerpting, though—too many charts and tables. But, you really should read the fourteenth chapter: "'In These Very Words': Methods and Standards of Literary Borrowing in the Second Century" by Charles E. Hill (available here). Well worth the effort. I was trained as a Classicist, so nothing he said was new, but if you are unsure about the stability of the text of the New Testament in the second century, this article will reassure you. Check it out!
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