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Here's a chart from Quickload that happens to be for a 357 Mag. Granted, a 22 LR will operate at a lower pressure and velocity will not be as high but the relationship between barrel length (bottom row of numbers), chamber pressure (red line and numbers), and velocity (blue line and numbers) will bear resemblance. As you can see, the slow burning powder in the 357 Mag cartridge peaks in pressure at about 1.5". However, as pressure drops off (red line) the bullet continues to accelerate (blue line).

Sr40Ken, There are many different burn rates for powder. Some examples: Bullseye totally burns up in 2 inches of bullet travel, Unique takes about 4" of bullet travel to burn up and W-296 takes a whopping 15" of bullet travel to burn up. Oddly enough, there's not much difference in burn temperature, peak pressure, and burn velocity so the time it takes (rated in bullet travel) is where the difference really comes into play. In essence, the longer the powder takes to burn, the higher the velocity will be. Of course, if the bullet runs out of barrel length, the rest of the powder will burn up in the air and create a muzzle flash.

 

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@Iowegan, I darn sure know I am getting in the weeds here. I wonder how far down the barrel in the graph you presented, is the given powder consumed. As the bullet moves, the volume increases behind the bullet. So, pressure can be decreasing even as powder is still burning.

We used to say in engineering school............mechanical engineers build weapons, civil engineers build targets. I am a target builder....
 

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Hmmm
Any good reloading manual would answer the OP query.

Years ago my shooting pal and I shot a 10" Contender barrel against a Marlin Camp 9 16.5"? With the same factory ammo. The camp 9 was almost always a few fps under the Contender. Proof is in the chili...
 

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Corndog, QuickLOAD is pretty nifty .... it allows you to set the barrel length where ever you want. This chart was generated using a .357" 158gr XTP bullet, 16gr of W-296 powder, in a 357 Mag case with the gun's barrel length at 7 1/2". If you set the barrel length long enough, QuickLOAD will also draw a vertical line indicating a "95% powder burn" at X inches. I ran this chart again only this time I plugged in a 20" barrel. The 95% burn line appears at 15.8", which is about 15" of actual bullet travel.

I don't know exactly where a 22 LR powder charge reaches a 95% burn but based on other data I have found; it has to be close to 10".

So, pressure can be decreasing even as powder is still burning.
Indeed, as indicated in the chart at 7 1/2". Pressure has dropped from 35k psi to just 7000 psi (blue numbers on the left). As the barrel length gets longer, pressure will continue to drop but velocity will continue to increase .... to a point. In the new chart I extended, MV increases to 1750 fps at 20". This is a pretty accurate number because I have chronographed a Marlin 1895C with this same load and it is very close to QuickLOAD's prediction.
yavapaisam, Not a fair comparison. A semi auto will always rob some velocity to operate the action. A T/C has a sealed chamber with virtually no loss of pressure.

There's a lot to be said about computing a gun's velocity based on barrel length. Fortunately, we have an instrument that works really well to take the math and guess work out of the equation. It's called a chronograph and it will tell you precisely what velocity your gun and ammo will produce.

We used to say in engineering school............mechanical engineers build weapons, civil engineers build targets. I am a target builder....
Sometimes I think I am the target.
 

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I'm still trying to wrap my head around powder burning at 6000 fps. All powder? different containers?
 

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SR40Ken, the burning gasses produced by modern smokeless gun powder expands at a rate of about 6000 fps. Some powders are a bit faster; some are a bit slower but most fall in the 6000 fps expansion range. Smokeless gun powder in its purest form can generate much higher expanding gas velocities but all powders have additives called "dope", a retardant that adjusts the powder to the desired burn rate. This makes the theoretically fastest possible bullet exit the muzzle at the speed of 6000 fps. When powders burn faster than 6000 fps, they become an explosive instead of a propellant. As an example, C-4 explosives generate expanding gasses at 26,400 feet per second .... not something you would want in your 22 rifle.
 

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Discussion Starter · #30 ·
Thank you very much from the bottom of my heart :) This table has helped me

Thank you all for responding to me

What I see from the attached table above is that there is no room between the 5-inch and 6-inch barrel, while there is a big difference between the 4-inch and 5-inch barrel

That's what I wanted Arafa actually the 4-inch barrel is ineffective for me..

Thank you all again
 

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Here's a chart from Quickload that happens to be for a 357 Mag. Granted, a 22 LR will operate at a lower pressure and velocity will not be as high but the relationship between barrel length (bottom row of numbers), chamber pressure (red line and numbers), and velocity (blue line and numbers) will bear resemblance. As you can see, the slow burning powder in the 357 Mag cartridge peaks in pressure at about 1.5". However, as pressure drops off (red line) the bullet continues to accelerate (blue line).

Sr40Ken, There are many different burn rates for powder. Some examples: Bullseye totally burns up in 2 inches of bullet travel, Unique takes about 4" of bullet travel to burn up and W-296 takes a whopping 15" of bullet travel to burn up. Oddly enough, there's not much difference in burn temperature, peak pressure, and burn velocity so the time it takes (rated in bullet travel) is where the difference really comes into play. In essence, the longer the powder takes to burn, the higher the velocity will be. Of course, if the bullet runs out of barrel length, the rest of the powder will burn up in the air and create a muzzle flash.

Thanks, that table provides a useful concept for those seeking subsonic. I guess super vs sub is not the only issue re noise perceived by the operator, since longer barrels are generally thought of as quieter. I guess this means perceived noise is a function of multiple variables: (1) pressure, (2) super vs sub, (3) distance of muzzle from operator, and (4) maybe others.
 

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You can't use that chart for getting to sub sonic because the powder used, W296 ain't going sub. Reduced loads of 296 can cause serious problems.
 

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Sr40Ken, The OP was talking about the velocity per inch chart, not the QuickLOAD chart, which I posted just to show the relationship between barrel pressure and velocity at different barrel lengths.

If you look at the QuickLOAD chart, you will see the velocity in a 3" barrel is well under the speed of sound (about 1155 fps). Further, this is a max load with W-296 so with a minimum safe load, a bullet will exit subsonic with a 4" barrel.
 

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I guess I best not go further with my load. 158 gr Everglades over Hodgdons recommended minimum w296 is going over my chrony dead on 1200 fps out of my 3" SP101.
 

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And keep in mind as altitude increases Mach decreases. Its also effected by relative tempature and humidity.
At least that was the physics around Mach capable aircraft.
One of the fighter pilot's I worked with was Cdr VanHoften who became a shuttle systems specialist. He had a diploma in fluid dynamics. He could mesmerize us with slide rule and pencil and paper figuring how many pounds of solids an F-4 ran into at 20k while traveling Mach 2. Great fighter pilot and best I could tell great scientist.
 

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GONRA, I don't understand your post ... would you mind sheading some light?
 

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I have 9, 20” Henry rifles paired with matching revolvers for almost all of them. There is an average 200fps speed increase going from a 5.5”-6.5” barrel to a 20”. Now those are across most revolver cartridges.

I have several 3”-3.5” semi autos with corresponding 4.25”-5” barrels. I see an average increase in speed between 70-150fps adding 1”-1.5” of barrel. That is across most semi-auto pistol cartridges.

What does that actually equate to in power? The faster a bullet is moving, the bigger the power gap becomes. Some quick math in 200 fps increments:

230gr bullet @ 800 fps = 327 ft lbs
230gr bullet @ 1000 fps = 511 ft lbs

That’s a net gain of 184 ft lbs over the previous.

230gr bullet @ 1200 fps = 735 ft lbs

That’s a net gain of 224 ft lbs over the previous.

230gr bullet @ 1400 fps = 1001 ft lbs

That’s a net gain of 266 ft lbs over the previous.

Those are small but realistic gains and the effect they have on muzzle energy. If you look back and compare the original 800fps @ 327ft lbs and add 600fps, it tripped in power. 75% speed increase created a 306% power increase.

Those are a close approximation based on firing a 230gr 45 ACP bullet from both 45 ACP and 45 Colt casings from 3.5”, 5.5”, 10” and 20” barrels.
 

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Thanks for breaking it down this way. Are these actuals? Did the 230gr bullet go supersonic from a 10" barrel?
My ACP and Colt loads are loaded very close to each other. I have a pair of Ruger Blackhawk convertibles I test all my loads in. I will have to lookup the actual from the 10” but this is the 45 colt load from a 5.5…


250gr Berry’s CPRN
9.5gr Unique Powder
Winchester WLP Standard or Magnum primers

Fired from a 5.5” stainless Ruger SA Bisley

1st Round 997 fps
2nd Round 1001 fps
3rd Round 1002 fps”


A disclaimer here. This is a max load for a lead bullet per Alliant load data.

Short answer is, yes. A 230gr 45 ACP hand load can break the sound barrier from a 10” barrel.
 
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