Rough cylinder opening

[penny_royal]

I have a new-production 940 that has been breaking in nicely everywhere except for cylinder opening. The face of the bold is slightly less than flush with the recoil shield, and the pin on the cylinder is scraping slightly as it comes off the bolt when opening the cylinder. Is the face of the bolt supposed to be completely flush, and should the face of the bolt and the left side of the opening that the bolt comes through be polished, or just left to work itself in over time?

 

[armorer951]

Yes, when the thumbpiece is pushed forward to open the cylinder, the bolt should come forward to the point of being flush with the breechface. If the bolt fails to come forward fully, the center pin will not be pushed fully forward during cylinder opening. If the center pin cannot move fully forward, there will be unwanted contact between the end of the center pin and the center pin cavity in the breechface, and at the center pin's interface with the front locking bolt.
You might check to see if part of the resistance when opening you are feeling is coming from the locking bolt catching on the end of the extractor rod during opening. Very common problem.

When the thumbpiece is pressed forward, the center pin should come flush with the end of the extractor rod, or just slightly above flush. You can check to confirm the center pin is the correct length by removing the cylinder, and standing it on the extractor end on a hard, flat surface, and pressing fully down on the cylinder, noting whether or not the center pin comes fully out to the end of the extractor rod.

Excessive end shake on the cylinder can also be a contributor to rough opening, as can a loose extractor rod. Be sure and check for these issues too.

The drag mark on the breechface caused by center pin contact is considered normal wear and tear. This area should not be polished.


Carter

 

[penny_royal]

Thanks, Carter. I went through that list and confirmed that the center pin is clearing the end of the extractor rod, that the rod itself is tight, and that as much as I could by manually manipulating it confirmed that there is no play with the cylinder on lockup.

Photo below; the bolt is a few thou below flush, and you can see the shiny spot on the left side it has started to wear in. Still feels very rough for the first 5 degrees or so on opening the cylinder. This is the very end of its travel; when pushing the thumbpiece forward, there is no additional movement.

This is a return-to-Springfield for correction, right? I am comfortable taking the thing down to bones and replacing a part, but don't see anyway from parts diagrams and disassembly videos where there is any place where the bolt can be fitted or adjusted to sit further forward.

 

[armorer951]

If it's new and under warranty I would recommend sending it in for repair. Normally, when fitting the new bolt, the pin on the end of the bolt may be a bit too long and has to be ground down to be flush with the breech.

What concerns me most is the apparent wear circle around the center pin hole in the breechface. This appears to have been caused by the boss on the extractor. In your photo, that wear ring looks like it extends below the breechface surface, and shouldn't be there.
Normally, contact between the boss and the breechface will cause the finish to wear off, but this looks abnormal in your photo, like there is an indentation there.

Hope you get the problems sorted out.


Carter

 

[tom 45]

My 360j was just like that...
It was very hard to open and the bolt face sat low.
I took out the bolt and with a set of jeweler's files dressed down the area at the base of the pin until the pin sat flush with the breechface. It works fine now.

 

[penny_royal]

I hadn't noticed the wear circle but yes, you can catch a fingernail on it so it's not just polished. Will call them today to arrange the return. Thanks again, Carter.

Good to know Tom, but as it looks like there's more than one thing going on here, will leave it to Smith & Wesson to figure out.