BUT I ROLLED ALL 6's!

Recently the question came up about a ranged attack roll of all 6's being a hit regardless of DEF against models with stealth.
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This is true however it still doesn't work against models with Stealth, because all shots further than 5" away are an automatic miss.
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Automatic misses always trump automatic hits.
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Therefore even though you rolled all sixes and it's a hit regardless of DEF, it is not an automatic hit, and the automatic miss from Stealth has priority in the rules.