Are the 3913 and 4013 exactly the same size externally...?...I'm getting interested in an older Smith da/sa for a carry pistol.

I don't think so. 3913 weighs 25 oz and the 4013 weighs 27 oz. 9mm vs .40 cal. The 4013 has to be beefier to handle the charge. I don't know the specs.

The 3913 & the 4013TSW are medium size frames. Besides the larger caliber & the double stack mag of the 4013TSW, they're very similar size. Exactly the same externally? Close.

But NOT the 4013. It's a single stack but on the large 45's frame. Completely different.

My 3914 weighs 25oz. & my 4013TSW pre-rail weight 27oz.

My 4013 weighs also 30oz.

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4013 vs 4013TSW barrel -01


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4013 vs 4013TSW barrel -02


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4013 vs 4013TSW barrel -03


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Even a 3914 & a 6906 aren't exactly the same, but they're close.

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4013TSW & 4056TSW (pre-rails)


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Waiting for the break of day

But the 6906 and 4013TSW have the same external dimensions....

The 4013 (as well as its rare cousin the 4014) is basically a 4516-2 in 40 S&W with an alloy frame.


Here are my "Salt & Pepper" boys. Only 550 4014 pistols were produced by S&W per Roy Jinks, S&W Historian.

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1st Signal Brigade, RVN '70

Close but the 4013 TSW has a slightly wider frame. I own a 6904,3914 and a TSW 4013. Some holsters will interchange but some will be to tight for the frame on the pre rail 4013. I carry all mine in the same holster but had to leave the 4013 in the leather holster for a couple days to let it slightly stretch before I was comfortable in drawing from it.
Hope this helps.