What is this hole under the lug

[maxxer2]

This is s&w 610-3. I don't know metallurgy so maybe this is needed?

 

[toroflow1]

It's for lube for the ejector rod. No, just kidding! BTW: sorry you in CA.

 

[maxxer2]

It's for lube for the ejector rod. No, just kidding! BTW: sorry you in CA.

Nod. Hence I can only buy 610-3. Even if other 610 are available online I can't buy them because they are not on the roster.

 

[jaymoore]

Dirt, rust, etc., clearing hole for the locking pin assembly. Probably also eases factory inspection to ensure the longitudinal hole is full depth. Barrels without the full lug don't need it since the lock pin protrudes out the front of the partial underlug, whether shrouded or not.

 

[Hawg Rider]

Dirt, rust, etc., clearing hole for the locking pin assembly. Probably also eases factory inspection to ensure the longitudinal hole is full depth. Barrels without the full lug don't need it since the lock pin protrudes out the front of the partial underlug, whether shrouded or not.

I don't have a clue about the hole in the full lug, and have never seen it before. But jaymoore's explanation is probably a good one. The hole shouldn't negatively affect the performance of the revolver, and that 10mm should be a fun and accurate shooter. Buy it and enjoy it!

 

[stang1911]

That's where the gas block go's for auto operation oh wait.

 

[gwpercle]

My un-expert guess is ... Drain Hole !

A place for excess cleaner , lubricant or ... water

To drain out . Here in louisiana we have lots of water , from the sky and the ground ...Louisiana is the Bayou State ... you fall in the bayou and get all wet ... the water can drain out easy .
Hole looks too neat to be Termite's ... dey eat up everything except the Cypress wood !
Gary

 

[handejector]

Dirt, rust, etc., clearing hole for the locking pin assembly. Probably also eases factory inspection to ensure the longitudinal hole is full depth. Barrels without the full lug don't need it since the lock pin protrudes out the front of the partial underlug, whether shrouded or not.

All of this is probably correct, plus it serves as a pressure release that prevents back pressure on a well oiled or greasy locking bolt.

 

[Yendor357]

Thread that hole. Plug it. Report back.

^that was a joke

 

[stansdds]

The 10mm Auto is such a powerful cartridge that when it fires, there is such a pressure wave that the forward cylinder lock needs to be able to vent the shock wave.

 

[Photog]

Someone put the muzzle break on the wrong side.....

 

[GypsmJim]

If it's needed for maintenance, wouldn't the Owner's Manual show it in the directions?

 

[Nomadmax]

Thread it and install a light

 

[tlawler]

All of this is probably correct, plus it serves as a pressure release that prevents back pressure on a well oiled or greasy locking bolt.

BWAHAHAHAHA!

You guys are about a week early, but just getting warmed up, I see!

 

[Alk8944]

The hole is a vent to assure the locking bolt will move freely as necessary. Without the vent the locking bolt could operate sluggishly if excess oil caused either air compression or a vacuum in the locking bolt hole.

handejector beat me to it! I didn't read every post before answering.

 

[stang1911]

If antifreeze is coming out of that hole you need a new water pump.

 

[JohnRippert]

'Ba-dum, tiss!' (rimshot for all the amateur comedians working their acts in preparation)

 

[jaymoore]

All of this is probably correct, plus it serves as a pressure release that prevents back pressure on a well oiled or greasy locking bolt.

Definitely a factor if the clearance with the pin is a 0.001" or less (in clean conditions.) If it's much more than that, assuming the oil hasn't congealed or is very thick, binding or other hydraulic resistance factors rapidly diminish for this small of a diameter. (Too many years running jig grinders and such! Bigger "piston/cylinder" assemblies are easier to produce air cushions and such. Usually you needs good surface finish on both parts and a 0.0005" clearance or less to get good "air float".)

Having never measured one of these pin bores, specifically, and compared compared it to the locking pin, which do usually have smooth finishes, possibly 16 RMS or better, I just made a SWAG.
I'd be surprised if the holes receive any more attention in manufacture than reaming. Likely they're just drilled, which means they're three lobed rough-finished messes, on a tiny scale.

Way down the rabbit hole of S&W revolver trivia! But fun to contemplate.

 

[444 Magnum]

Glad you posted this OP. I have the same on my 586's and was wondering myself.

 

[Bobbysixkiller]

I would think in case it gets fluid behind the locking bolt that it won’t hydro lock. Like a piston/cylinder full of liquid. As liquid doesn’t compress so if it’s full of fluid it will drain and you can still open the cylinder. Say it was dropped in water etc. my guess anyway.