Re-thinking the whole concept of handgun compensators...

[Jim March]

Folks,

As most know I've been modifying my Ruger NewVaq357. I have a working gas-powered system for auto-ejection of empties as I shoot. Seriously. Right this moment I'm putting the finishing touches (just cosmetic) on the 3rd try and will be taking it to the range for testing and a photo shoot either today or tomorrow. More on that later.

Meanwhile, I've learning a LOT about how serious the muzzle blast power is on a 357Magnum, and how to direct it and tap it. I'm mainly using those gasses to power the autoeject system but the original plan was to also do a compensator.

Well until I get access to better tooling, the comp plan is on hold.

Basically, I've been trying to add a tube around the original barrel, extending forward about 1/2 to 2/3rds of an inch and using that as a gas pressure chamber by "capping" it. In other words, from the bullet's point of view, the bullet comes out the original barrel, enters an area that is over-bore (by a fair amount) and then passes through a final constriction that is still over-bore (bullet never touches it!) but is still smaller than the area just behind it. This final constriction point is what I call the "endcap". I figured that would trap a LOT of gas pressure.

Holy crap did it ever! Enough to completely detonate the original brass "endcap" piece. Once re-done in stainless steel and aircraft aluminum (using the upper 3" or so off an old motorcycle fork tube and the original screw-on cap for same) those pieces "held" but the screws holding all that to the barrel and sight base were bending under the pressure and I stopped at around 2/3rds of a box of full-house 158gr 357 ammo.

I've now rebuilt it all so that there's one more screw holding it to the sight base and finally, there's no ending "cap" constriction. I figure this'll give me plenty of auto-eject pressure in 357 but I won't have much extra to tap for a compensator. I'm OK with that...it's a bit annoying but what the hell.

Here are my notes on what a really serious handgun compensator chamber might look like:

So far as I'm aware, none of the current designs work like that for handguns. They do for the major-grade comps you find on 50bmg rifles, such as:

 

[Bob Knizner]

Hi Jim-

The comp on my S&W 500 has some similarity to your "ideal design". It actually has a lip just inside the very end of it to act a little like the cap in your design.

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I wish that this comp had the rearward gas deflection like the 50 BMG rifles!

Bob

 

[Jim March]

Ah. Yeah, I figured somebody was doing something like it.

To get rear-and-sideways deflection you'd have to make the chamber slightly fatter than the barrel, and that makes for a funky holster. I had to completely redesign my holster to make my setup work.

On a gun with a fairly thick barrel wall (narrow yet potent caliber like the 357Mag, 356GNR or 357Maximum), rear deflection would be easier.

 

[Standing Wolf]

Stand back. Keep your voices down, please. No shoving or pushing. We're about to witness the reincarnation of the semi-automatic pistol, unless perhaps the automatic pistol, though it may evolve into the... Well...

Seriously: I made it through a physics course in high school without understanding the mathematics involved, so don't take my word for it, but I have a hunch a peek into a pneumatics text might be of use.

I like the idea of using gas from a barrel to do useful stuff, but must admit I've never understood how to keep things clean and/or keep them from getting hotter than the ductwork in Hades' furnace room.

 

[Jim March]

I'm seeing no evidence of crud buildup...but then again I wouldn't want to shoot black powder with this kind of thing .

In fact, I'm pretty sure now that gas-operated anything couldn't have been invented until after smokeless powder was a reality. It was apparently experimented with in the black powder era as some gas-operated systems started to ship not long after the smokeless changeover. By WW1 we saw a fair number of gas-operated autos, although some like the Maxim were still purely recoil-driven.

 

[kozak6]

Alright, what you need to do now is tap the gas to run a piston to recock the hammer, which will cycle the cylinder, and then have it eject the empty. Just don't forget a disconnector, as you don't need full auto.

After you get that figured out, you need to work out a way for the gun to automatically reload the cylinder from a tube magazine as you shoot.

 

[Slopemeno]

I think you'll find there's a lot of "work" happening inside an expansion chamber comp. At my shooting league on of our tinkerers had the whole front half of his home brew comp blow off and actually score a low D hit at 50'. He was shooting .45 ACP with 155 grain bullets making 165 PF.

 

[Jim March]

Ohkay, so I'm not the only one having these issues .

 

[jersey_emt]

This sounds really cool. I can't wait to see what you've come up with.