I have one of the chief special m36's that came with hogue rubber grips. The downside is a lack of a grip pin in the frame, meaning I have to come up with something to hold wood stocks in place.

I've tried to order the grip pin from both ebay and numrich, and both times I was shipped a solid pin, not a roll pin like all of my other revolvers have. Making it worse, the solid pin ain't gonna fit in the little hole.

Any ideas what size roll pin should be used? I tired cutting a nail down, but it isn't the best solution since a 4d is a hair small and a 6d is too fat.

Most auto parts stores have .125" (1/8") roll pins, which should fit. The S&W style OEM roll pins are approx. .120" X .600-.625".

Dorman AutoGrade 44613 - Roll Pin | O'Reilly Auto Parts

The OEM pins should also be available from S&W Customer Service. 1-800-331-0852. If you call them and explain your circumstances, they may send you one free. Have your serial number at hand when you call.

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Ret. LE, FA Instr, S&W Armorer

You can take a Drill Bit of the appropriate size, cut it to size with a Dremel, slightly round the ends and Locktite it in place IF the friction fit is not perfect. If you get just the right size Bit, you will not need the Locktite. I actually like the drill rod over the roll pins because they are perfectly smooth and will not tend to enlarge the relatively soft Walnut grips on Revolvers. I've done this many times and it works great - but instead of using Drill Bits I have a complete set of blank Drill Rod that I invested in many years ago.

I also make my own punches if I do not have the exact size I need. Drill Rod can be purchased at McMaster-Carr, MSC or most Machinist Supply Company's. If this is just a one time use - use the Drill Bit.

I make it a point to do this on Revolvers that have Ivory, Stag, Bone or similar grips as sometimes the Roll Pins tend to dig in to the grip panels and enlarge the holes. I have NEVER been a fan of Roll Pins as I think of them as a "cheap" way to do retention.

The obvious answer would seem to be 5d?

I went out and mic'd one (a roll pin on a S&W, not a nail) and it measures .1175", so I am gonna guess 3mm.