Pistol Caliber carbines and power

[CCCLVII]

Recently I got to shoot one of those 9mm high point carbines. After running it over the chronograph I saw it was gaining less than 200 FPS from the 16 inch barrel over his 5 inch pistol.

Why is it that Revolver rounds seem to gain so much more power from a carbine than a semi-auto round?

I know my 357 magnum gains about 350-450 FPS from most factory loads from a Carbine.

[Metal god]

I think a 357 round is hotter period . When you look at some balistic charts the average 357 round seems to be a bit hotter then the average 9mm round .It also shows how much powder is wasted in the 357 round out of the shorter barrel.

[arch308]

As I understand it revolvers lose a little pressure thru the gap between the cylinder & barrel. That is eliminated with the carbine. Pistols have no such gap.
Just a guess on my part.

[Metal god]

revolvers lose a little pressure thru the gap between the cylinder & barrel.

Forget my last post I like this answer :cool:

[Brian Pfleuger]

9mm has very little powder space. 357mag has much more. 9mm will max out speed somewhere in the 12-15 inch range, actually lose speed thereafter and not gain much after 6 or 8 inches. I'll have to check QuickLoad later for a better idea.

The short answer is, more space for powder means better use of available barrel length.

[Deja vu]

Revolver bullets tend to have much more case capacity than bullets for semiautomatics.

[Magnum Wheel Man]

Semiautos have to be tuned to function / operate the action, burn rates & pressures are often softer on auto cartridges than with revolver cartridges...

that said, I'd bet you could load some 9mm with a slower powder, & may gain some more out of the longer barrel, but also may not get the carbine to cycle correctly...

... & of course the barrel cylinder gap makes a big difference ( probably at least 100 fps ) IIRC I gain at least that much in my Contenders with revolver cartridges, with similar barrel lengths ( barrel & cylinder added together when measuring on the revolver )

[jmortimer]

Powder has a big role in this. Consider the rim-fires - they pick up a whole lot of speed. .357 sig picks up 250 fps or so. Cylinder gap is an issue as noted, but case volume is a factor as noted. As most know its all right here
http://www.ballisticsbytheinch.com/calibers.html

[SHR970]

A few things come into play here.
The first, which has already been covered in this thread is the difference in the amount of powder space available / used between the rounds. In most given powders for similar bullet weights the 357 uses around 50% more powder. For the biggest difference, the 357 uses powders generally regarded as too slow for the 9mm and these powders are used in even larger charges.

The second and more importantly, the semi auto actions are almost exclusively blow back actions. You are stuck using powders and in amounts that work these actions without beating them to death. You are also utilizing a fair amount of energy to overcome the friction of expanding brass in the chamber and actuate the heavy weight bolt and spring assemblies. Compared to the difference of loss at the cylinder gap of a revolver and the losses here is night and day.

Third, a revolver caliber carbine goes from a cylinder gap loss system in a revolver to a sealed chamber system in a rifle. The gap losses are now added to the energy available to push the bullet. Vis A Vis a pistol in which you start with a certain amount of loss moving the locked slide / barrel and now we add the losses at the breech when you have a blowback pulling the brass out when there is still pressure in the barrel. The slower the powder used, the more this exacerbates the loss effect.

Fourth, in a semi auto carbine, if you are on the too slow end of powders and in bigger charges you can be spending energy deforming the brass as it comes out of the breech.

When you add all of these losses up, you have bigger losses in the semi auto system vs. the locked breech / revolver system.