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Please explain revolver internal chamber rings

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rajbcpa

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At the forcing cone end of each of the cylinders in all of my S&W DA revolvers is a visible constriction ring inside the chambers - about a few thousands of an inch smaller than the measures of the chambers at the hammer end.

What are these internal rings called and what purpose do they serve? Are these present in non-S&W revolvers? I have a Colt SA reproduction (Pietta) that also has these rings.
 
It's called a throat and ,ideally,it is the same diameter as the grooves in the barrel and a hair smaller than the bullet.It helps center and stabilize the bullet when the gun is fired.On some guns that use rimless cartridges it determines the headspace since the rim can't.
 
Not wanting to hijack rajbcpa's thread but this is interesting to a new revolver guy. My 3" 65-3 has the throats and they are smaller than the bullets I handload. This seems to indicate that the throats reshape (squeezes down) the bullets before they enter the larger forcing cone. Isn't this virtually the same as loading undersized (smaller diameter) bullets which we have all been told tends to reduce accuracy. What am I missing here? I'm old but still learning:)
 
oldgranddad said:
Okay. Then why would they be in a .357 magnum 65-3?
Click to expand...

That info is incorrect.... the throats are not for limiting a magnum cartridge from being chambered in a .38 special revolver, that's a function of the chamber length itself, not the throats in front of them.
 
oldgranddad said:
Not wanting to hijack rajbcpa's thread but this is interesting to a new revolver guy. My 3" 65-3 has the throats and they are smaller than the bullets I handload. This seems to indicate that the throats reshape (squeezes down) the bullets before they enter the larger forcing cone. Isn't this virtually the same as loading undersized (smaller diameter) bullets which we have all been told tends to reduce accuracy. What am I missing here? I'm old but still learning:)
Click to expand...

As long as the throat is not smaller than the barrel,it's perfect.If it is smaller,lead bullets probably won't group well,but jacketed might.
 
Revolvers with long chambers, like the Governor or Taurus Judge suffer some performance loss with hand gun cartridges.

It's been said that early Colt 1917's were bored through.
 
arjay said:
As long as the throat is not smaller than the barrel,it's perfect.If it is smaller,lead bullets probably won't group well,but jacketed might.
Click to expand...

That makes sense. So if I'm shooting a revolver with throats in the charge holes, it's unlikely that going up a .001/.002 on a LRN bullet diameter is going to help reduce group size unless the throats are too large. Yes?
 
Right.You should be able to drop a bullet in there and it will hang up.If it falls through,they probably won't group well.45 Colt seems to be the main culprit in S&W and Colts.
 
the 'rings" you actually 'see' are the step in the chamber from the case diameter, to the smaller throat, this step is due to the chamber reamer (cutter) making the cut, ,the reduction in size gives the appearance of "rings", ergo, the step....
some confuse this with the 'leade' another story, and in a rifle, the "shoulder".
 
oldgranddad said:
That makes sense. So if I'm shooting a revolver with throats in the charge holes, it's unlikely that going up a .001/.002 on a LRN bullet diameter is going to help reduce group size unless the throats are too large. Yes?
Click to expand...

Yes. The bullet will be sized down by the throat. The older cartridges were made like 22lr rimfires many years ago. The bullet was the same size as the outside of the case. They used a heeled bullet. The chamber was bored straight through. They were also outside lubed. The later inside lubed bullets were made small so the bores were made small to make up for it. The throat was then added to the cylinder.

Some revolvers were made with bored straight cylinders. The early Colt Army model in 38 Long Colt was made that way and is reported to be able to chamber the 357 Magnum. Not a good idea. Also, as someone mentioned, the early Colt M1917 revolvers were made that way.

For more info, look up the 41 Long Colt cartridge.

If you are getting good accuracy from your revolver I wouldnt worry about the throat size. You could push a bullet through and then measure it if you are interested. If you get a lot of leading and accuracy is poor, it could be a problem.
 
Other than intentionally machined...

Other than features that intentionally machined into the chamber such as the throat and possible chamfering the cylinder walls are better the smoother they are. Ideally they should be mirror smooth. Rough chamber walls can cause sticking of cases.
 
An undersized throat will swage down the bullet and give a less than perfect fit in the barrel (if the barrel is the correct bore size). I've had 3 revolvers with undersized throats, that when later corrected shot better with less lead splatter.
But, it's a matter of expectation also. I won't keep a target revolver that shoots over 3" at 50 yards.
 
Well I have a few Army Navy colts and one of those is in the old 38 long colt chambering which is straight bored threw the cylinder. The other Army Navy I have is an early one chambered for the 38 special and has the throat. Also have a throw down H&R top break with a straight bored cylinder in 32 long. That one is for throwing after slathering all six at a target. Man does that one spit powder lead and what ever else. Another I own is a Swedish Nagant with just a gradual taper in the chamber. Beautiful old revolver and I hope to load some ammo for it that will shoot good one day.
 
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