Very basic question about revolvers

G

ghbucky

New member
I know that revolvers work.. as in they go bang and bullet goes down the barrel and on down range with very precise repeatability.

I understand the principle of how closed bolt systems work. I'm missing a step with revolvers.

When the charge sends the bullet out of the cylinder and jumps to the forcing cone, there is now an air gap behind the bullet in the barrel. Why doesn't the charge just completely vent out of the cylinder gap at that point?

How is pressure maintained?
 
For the same reason that a pin hole in a mylar balloon does not vent all the gas instantly. The cylinder-barrel gap is too small to let the very large volume of gas escape before the bullet is pushed out the end of the barrel.
 
You do lose some velocity due to the gap compared to the same cartridges fired in closed breach guns with the same barrel length. But it isn't enough to make a real difference.

It is also important to hold revolvers properly to avoid damage to your hands from the gases venting from the barrel/cylinder gap. Particularly with powerful rounds.

http://www.freerepublic.com/focus/news/2313371/posts
 
Actually, pieziometric measurements show that maximum pressure is attained when the bullet covers the gap - so no loss of peak pressure. As others have stated, the gap does vent pressure but what remains is still enough to accelerate the bullet.

Here is data which helps to quantify the effect of cylinder gap on cartridge performance.

http://www.ballisticsbytheinch.com/gaptests.html



.
 
Thanks all!

It is also important to hold revolvers properly to avoid damage to your hands from the gases venting from the barrel/cylinder gap. Particularly with powerful rounds.
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This is exactly what prompted me to ask this question.

I was at my local indoor range yesterday and a couple of guys were acting rather goofy. It was just me and those 2 on the range. They finally called to me and asked me to fire their rental gun.

At first I said, no thanks. But they told me it is a .500 S&W. I passed again, but finally decided that the last thing we needed was 2 non-shooters getting in trouble with a beast like that without some help. I can't imagine what thumb burn would look like on that thing!

Turns out the gun was non-operable. The range hadn't bothered to clean the thing so the cylinder was frozen.
 
Vital teaching point !!!!

Why doesn't the charge just completely vent out of the cylinder gap at that point?
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Think about the path of least resistance. ...... :)

I can't imagine what thumb burn would look like on that thing!
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There are pictures on the internet and it's not pretty. When I demonstrate a revolver. I Loosely fold a piece of cardboard over this area. The damage is a great teaching aid.. :eek:

If there is a problem with the revolver, the potential hazard gets multiplied. Look at the Taurus revolver rifle and you will notice a shield that redirect this flash. .... ;)

Be Safe !!!!
 
ghbucky said:
I know that revolvers work.. as in they go bang and bullet goes down the barrel and on down range with very precise repeatability.

I understand the principle of how closed bolt systems work. I'm missing a step with revolvers.

When the charge sends the bullet out of the cylinder and jumps to the forcing cone, there is now an air gap behind the bullet in the barrel. Why doesn't the charge just completely vent out of the cylinder gap at that point?

How is pressure maintained?
Click to expand...
Whats really strange ...is when identical loads of calibers like 9mm Luger , 10 mm Auto and 45 acp , are fired in both a semi-automatic handgun and a revolver , like a Ruger Convertible Blackhawk , and the velocities are recorded ...
The strange part is the revolver shows a few fps higher velocity than when fired in the semi-auto pistol with no forcing cone gap , in every instance !

"OK Lucy ...Splain this one to me !" Strange but the gap doesn't seem to matter .
I have an idea of what happens and the answer(s) is rather simple .
Gary
 
OK Lucy ...Splain this one to me !" Strange but the gap doesn't seem to matter .
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I'm not Lucy but here goes. Slide movement has nothing to do with it. Semi slides barely move or not at all before the bullet has left the barrel. It has to do with the difference in how semi's and revolver's barrels are measured.

The barrel of an auto is measured from the breech face to the muzzle and for the revolver, from the forward end of the cylinder to the muzzle. In other words, a 5" auto has effectively a shorter barrel than a 5" revolver. In a 5" 1911 shooting 230gr ball, for example, 1.25" +/- is eaten up by the length of the cartridge vs a 5" revolver shooting the same load. 3.75" of usable barrel length for the semi vs a full 5" for the revolver.

Longer barrel, more velocity.
 
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Never stand beside the gun because of the side blast. I used to take a plain sheet of legal size (regular is too short) and with the muzzle pointed down range, drape it over the gun and hold the ends together under the trigger and pull down to tighten over the gun. Fire the gun and watch what happens to the paper.

It always impressed the jr shooters to not stand forward of the shooter's shoulder
 
gwpercle said:
Whats really strange ...is when identical loads of calibers like 9mm Luger , 10 mm Auto and 45 acp , are fired in both a semi-automatic handgun and a revolver , like a Ruger Convertible Blackhawk , and the velocities are recorded ...
The strange part is the revolver shows a few fps higher velocity than when fired in the semi-auto pistol with no forcing cone gap , in every instance !

"OK Lucy ...Splain this one to me !" Strange but the gap doesn't seem to matter .
I have an idea of what happens and the answer(s) is rather simple .
Gary
Click to expand...

https://www.shootingtimes.com/editorial/revolver-vs-semiautomatic-pistol-a-ballistic-oddity/360682
 
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