The 4013 single stack large frame also has an alloy frame like the 4013TSW (either railed or pre-rail).
The 4013's robustness is in the barrel dimensions.
My 4013's slide & barrel weigh 17oz.
My 4013TSW pre-rail's slide & barrel weigh 14oz.
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4013 vs 4013TSW barrel -01
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4013 vs 4013TSW barrel -02
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