Pistol cylinders: serious question

[Widder, SASS #59054]

When I bought my first Ruger Super Blackhawk (or maybe it was a Blackhawk in .45 Colt),

the chambers were recessed for the case rims.   Ruger later did away with those type cylinders

for those big caliber pistols.

 

I have read and I have been told that one of the main reasons for cylinders with recessed chambers is to prevent

cartridge blowout at the rims.

 

BUT,  they (Ruger and others) still use cylinders that have the rims recessed for the chambers on Rimfire pistols.

 

WHY?    Is it a significant safety factor for rimfire?

 

..........Widder

 

[Subdeacon Joe]

My guess is that because rimfires fire by crushing the rim it is an issue of reliability.  

[Colorado Coffinmaker]

 

Hi Widder .. 

 

Partly/Mostly what Subdeacon Joe said.  Going back to the party of the first part.  Modern pistol cartridges are extruded with a "Solid Head."  The recess for the Case Rim sounds nice, but the case rim is below the bottom of the "Solid Head."  For that reason, a Blow-Out is simply not going to happen.  The working portion of the case head is completely supported by the chamber.  Some makers (Freedom Arms) still recess for the cartridge rim, but that process is most probably the result of already having that tooling.

 

For Rim fire, the recess is to prevent the rim from deforming when being hit by the firing pin.  Deforming of the rim is also is also why Henry and Winchester used a dual strike for rimfire cartridges.  A recessed chamber would make much more sense for older Balloon head cartridges although modern rimfire are still Balloon head.  Modern rimfire might still be subject to Blow-Out but would need a very thin case indeed.  Although the firing  pin strike might provide enough deformation to thin the Balloon head.  

[Knarley Bob]

My guess, is that most cases started out as rim fire. And would blow our.

But when center fire took over the rim was solid, and not likely to do that.

.22 Rimfire is still a rim fire, and needs a little "containment" ?

[Eyesa Horg]

Mr. Widder,

I had a Blackhawk .45 with the recessed cylinder you describe. It was a pain for the LTO to check, so I had a machine shop trim it down. Cold blued with Oxpho blue from Brownell's and never had an issue. The LTO's were pleased. Cost me $35.

[Joke 'um]

Containment when firing is probably part of it.  If you look at a loaded revolver from the shooter's point of view, you will most likely see the edges of the cases visable beyond the edge of the recoil shield.  The part of the rim sticking out this way is vulnerable to impact should the revolver be dropped or otherwise roughly handled.  If a centerfire, this is no big deal.  Impact on a rimfire case could be disastrous.  This is a big reason rimfire cylinders have recesses for the case head.  Just my $0.02.

[Pat Riot]

Here is link regarding recessed chambers in rimfires.

 

https://www.americanrifleman.org/articles/2014/10/28/pinned-and-recessed-smith-wessons/

 

Protection of the rim is the reason. 

There are lots of answers to this on other forums but we aren’t allowed to post links to other forums.