Detent on yoke question

I was cleaning/lubing up some of my guns the other day; I'm headed on a rather long military deployment and don't want to come home to a bunch of "freckles" if you know what I mean.

I noticed my 1917 M&P has a detent in the yoke and a small machined recess on the frame to match. When did S&W stop doing that? And why? Seems all it does is make the cylinder a little tougher to swing open.

Actually the detent, spring and plunger work to hold the yoke open , not closed. I don't think it made it long after WWI

I only have two revolvers with yoke detents a TL and a Brazilian 1917 made in 1938 so they used the detents at least until 38. I'm not sure about the second run of Brazilians after WWII.
steelslaver is correct about the reason for the detent, think cavalry and trying to reload a revolver while on horse back without the cylinder closing by itself.

Cyl/yoke detent hold open device:

A classic old feature to keep the cyl open when loading/unloading and prevent it from slamming closed if the gun is tipped to the right slightly and scratching the recoil shield with the extractor star.

The cylinder hold open device or detent was introduced on the very 1st hand ejector, the ".32 HE Model 1896, 1st Model" thru the ".32 HE Model of 1903 - 2nd Model" thru 1904. It was used and continued in pre WWI K frames beginning on the ".38 M&P Model of 1899" thru at least the pre 1919 ".38 M&P Model of 1905 - 4th Change", and also the N frames beginning with the 1908 44 Triple Lock.

By the Mar 10, 1919 change order: all cyl hold open detents in all frame sizes had been ordered eliminated. However, likely due to many surplus Model 1917 yokes being used from inventory, they are still found in most N frames pre WWII, and even thru some post war Transitional N frame HEs.

Another example of old world panache Smith was known for that we won't ever see again. And very easy to add to any later model Hand Ejector. To install a detent in a gun that doesn't have one, Drill the hole in the yoke hinge with a # 37 drill bit to a depth of .890" for the N frame, and cut the shank off of a #38 drill bit that slips easily into the hole in the yoke.

Use a sharpie pen to blacken the frame side of the hinge. With spring and plunger installed, install the yoke/cyl assembly in the half way open position. Then pivot the cyl to the full open position that the cyl clears the frame where it rubbed, remove yoke/cyl assembly. Center punch and drill the dimple shown above at the end of the inscribed line in the black ink.

Important Note: if you remove the yoke beware of the cyl detent pin and spring! If you aren't careful, it can launch across the room to no man knows where! If it's missing, that's likely what happened to it.

TO MAKE THE MISSING PARTS:
Although the yoke stop spring is available here: Smith & Wesson 1917 Revolver Parts, Schematics | Numrich
The yoke stop (pin) hasn't been in stock for years.

If you have a parts stash of old parts, it's not difficult to substitute pins and springs that'll do the job.

Original parts just aren't found and are too easy to make to hunt for them. Cut the shank off of a numbered drill that slips easily into the hole in the yoke. For K or N frame, pins are in the .540" to .570" length range. The yoke detent pin diameter measures .100" to .101"; and is dome SHAPE on one end. Use a BIC lighter spring cut to about ½".

Install spring and pin with domed end out. You can experiment with different spring lengths for just the right tension. If the yoke pivots too tightly cut a coil or two off the spring.

Plunger shown here in bottom of yoke and has a spring underneath it:


Photo credit: handejector

You guys are awesome. Thanks for enlightening me!

hkcavalier said:

I was cleaning/lubing up some of my guns the other day; I'm headed on a rather long military deployment and don't want to come home to a bunch of "freckles" if you know what I mean.

I noticed my 1917 M&P has a detent in the yoke and a small machined recess on the frame to match. When did S&W stop doing that? And why? Seems all it does is make the cylinder a little tougher to swing open.

Click to expand...

Thanks for your service to the good ol' US of A!

As per instructions from folks in this forum I used in my Brazilian the flint and spring of a BIC lighter. It worked quite well !

Regards, Ray

If you remove the cylinder, do it in a large plastic bag to avoid launching the pin to a place where it can never be found. A cool worthless feature on some old revolvers.

sodacan said:

If you remove the cylinder, do it in a large plastic bag to avoid launching the pin to a place where it can never be found. A cool worthless feature on some old revolvers.

Click to expand...

Good advice.

But once the open cyl falls towards the frame with the sharp cornered extractor star pushed to the rear while you're ejecting empty cases and puts a nice scratch in the bluing on the back of the recoil shield or the wood grip, it suddenly becomes a lot less of a worthless feature!

Take note of how many guns one can observe at gun shows with these tell tale scratches.

Ray said:

As per instructions from folks in this forum I used in my Brazilian the flint and spring of a BIC lighter. It worked quite well !

Regards, Ray

Click to expand...

I would highly recommend against using the flint. It's so hard it will chew a deep gouge in the frame hinge in no time.

Thanks Hondo44, I´ll see to that, regards, Ray

Thank you for what you do. I pray that you and all our troops make it home unscathed.

I have a 1917 Brazilian, 2nd shippment that had the hole and detent drilled but not used. I had a dozen pins made and springs and installed one in it. Nice feature that I like. I also use 800 grit sand paper on the back of the extractor star to take all the sharp edges off. I do that on all my revolvers. Even my cheap Rossi's.

Hmmmmm........My Registered Magnum #220 has a hold open detent. And, it was made in 1935.

tombstonegunsmith said:

Hmmmmm........My Registered Magnum #220 has a hold open detent. And, it was made in 1935.

Click to expand...

That would be the norm for all pre war N frames and even some post war transitional N frames.

To be clear, my gun is a K frame M&P made in 1917, not a “1917”.

hkcavalier said:

To be clear, my gun is a K frame M&P made in 1917, not a “1917”.

Click to expand...

Thank you for your service to our country!

I understand that. The existence of the detent in the N frames, like the 1917 is a different situation than your M&P.

Your M&P has the detent because it was made before the detent was eliminated for the M&Ps as shared in post #4.
You apparently have a ".38 M&P Model of 1905-4th Change" (1915-1942).

Stay safe my friend! Many prayers for ya'lls Safe return! Go with GOD!

THE WHYS AND WHEREFORES

I wasn't there at the time, but I hear tell the "hold open detent" came to be in order to help shooters at the firing line comply with a range command which called for weapons to be placed open on the bench. (??)

Ralph Tremaine

hkcavalier said:

When did S&W stop doing that? And why? Seems all it does is make the cylinder a little tougher to swing open.

Click to expand...

The "why" S&W dropped the cyl hold open detent I'm sure, was to lower cost of production.

If your detent makes the cyl "tougher to swing open" it could be that there's rust or crud in the hole. And if not, you could snip a coil or two off the spring under the pin to relieve the tension a bit.