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Discussion Starter · #1 ·
I have read on the forum that a longer barrel will increase velocity and that a shorter barrel will not decrease inherent accuracy, although shorter sight radius makes accuracy harder. There have to be some limits on this. At what length will a barrel start slowing down a bullet? What barrel length is too short for accuracy? Let's say a 9mm piece so we have that in common.
 

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With snubbies, you not only get a shorter sight radius, you also get lighter weight, especially less weight out forward at the muzzle. This also tends to magnify shooter error. Have gotten some excellent accuracy with 2" revolvers on a good day, but it's a lot harder to do than with even a 4" barreled gun. Not a less accurate gun, just a harder gun to shoot.

As for velocity in a conventional handgun cartridges, you need to get into rifle length barrels or specialty pistol length barrels to really see the point of diminishing returns or a point of no gain. A 357 mag or 44 mag is a MUCH faster shooting cartridge in a rifle barrel. Milder cartridges, less so.

Velocity in a handgun, though, needs to be considered as only part of the load package. Really needs to match the bullet type for the job at hand. As an example, for self-defense work, penetration is as much dependent on bullet type as it is on velocity and, as always, bullet placement is still number one.
 

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I shoot .38/.357 magnum a lot. I load my own, and test regularly with my chronograpgh. My go to revolvers are my 4" Smith 66, 4" GP100 , 2.25" SP101 , and my 2" KLCR . 357. (and yes, I know the GP100 is 4.2", and KLCR is 1 7/8", but I generally call them 4" and 2")

My 4" revolvers consistently give me between 150-200 fps faster velocities with any given load in .357 Magnum over the 2" magnums. And usually about 100 fps more with .38 special.

I still manage to get 158 gr LSWC's up to 1350 fps out of the 4" guns, and 1150 fps from the 2" guns. Still respectable from 2"ers. So, when you hear "There's no advantage from a 2" .357 magnum over .38 ", it is simply not true. You won't see any 158 gr .38, +P or not, close to 1000 fps, much less 1150!

For the critters down here, 2 or 4 legged, those velocities will easily get the job done!
 

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Bill West, Sometimes a visual aid helps with understanding barrel length versus velocity. In the below QuickLOAD chart, I plotted a 357 Mag with a 140gr bullet. The Red line represents chamber pressure which peaks sharply in just 1"of bullet travel then begins to peter out as the bullet travels down the bore. This trace does not take the revolver's B/C gap into account so actual chronographed velocities will be a few percent less.

The Blue line represents velocity ... starting at zero bullet travel. After 1 inch of bullet travel, velocity has climbed to about 600 fps. By 2 inches of travel, velocity has increased to almost 800 fps. At 3" ... 1050 fps, at 4" ... 1250 fps. At 5", the bullet is traveling at about 1350 fps and at 6", about 1450 fps .... so, about 100 fps per inch but as you can see, velocity continues to climb as barrel length increases ... but at a slower rate than in the first few inches. It takes about 15 inches of bullet travel to totally burn all the Winchester W-296 powder so velocity will peak out at about 20 inches of bullet travel. If a barrel is longer than 20", this particular load may actually start to decrease in velocity.



Keep in mind, other bullet weights and specifically other powders will develop totally different velocities but will still resemble the basic concept.

As for accuracy .... indeed a longer sight radius will help but it is not the only determining factor. It takes about 4" of bullet travel to establish enough velocity where the rifling will spin the bullet fast enough to maintain downrange stability. It is very common to see 9mm or 38 Special bullets fired from short barrels turn from nice round holes in a paper target at close range to "key holes" at more distant ranges. Of course accuracy goes down the tubes when bullet start to tumble. Most bullets fired from a short barrel will maintain stability and acceptable accuracy to 15 yds but by 25 yards, it's not surprising to see them tumble (oval or key holes in the target).

If you take practical things into account, a snub nose revolver or sub-compact pistol's intended design is for close up self defense ... 5 yards or so. These short barreled guns do not make good range or target guns ... typically too punishing to shoot much.

When real accuracy counts ... like in NRA bullseye competition, a 6" revolver or a 5" pistol is the most popular barrel length. Both take advantage of the stabilizing spin rate and sight radius. Anything past 6" starts getting unwieldy. For an "all purpose" revolver, a 4" barrel is a good compromise ... long enough to develop decent velocity and have a decent sight radius, but short enough to be concealable. Every barrel length has its pros and cons so it's really a matter of matching the gun to the application.
 

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I was going to reply with some observations, but Iowegan's explanation and illustrations just put me to shame :) Well explained Sir, well explained!
 

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:rolleyes: Iowegan ... Ever pragmatic & informative
 

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Discussion Starter · #7 ·
I want to thank you all for the information.

Iowegan, your knowledge is downright frightening. Do you give tips on sporting events? I see a way to make a little money.
 

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I had marlin 44 mag rifles in 16 20 and 24 inch and the 20 inch was the fastest with all loads and the 24 inch was always slightly slower than the 20 inch and the 20 was 200 fps faster than the 16 inch. The same results were obtained in 45 colt.
 

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bwinters, Your data for the 44 Mag rifles follows the same path as the above chart for 357 Mag. If you tried 44 Specials in those same rifles, my bet is ... the 16" barrel would chronograph the fastest, 20" would be slower, and the 24" the slowest. Why? 44 Specials use faster burning powder than magnum cartridges. The same would hold true if 38 Specials were used in a rifle versus 357 Mag ammo.

I think it's important to note ... with handgun cartridges loaded in actual handguns, you probably won't find a barrel long enough where velocity starts to chronograph slower. Fast burning powders (ie Bullseye, AA#2, Red Dot, etc .... build up velocity much faster than slow burning powder but even though the powder is totally burned up in 2" of bullet travel, the bullet will continue to accelerate for about 8". Of course acceleration won't be as great at 6" as it was at 2" .... but it will increase. Mid-burn rate powder (ie Unique, Universal, Power Pistol) burn up in about 4" but continue to accelerate to about 12". With slow burning powder (ie 2400, W-296/H-110, Lil'Gun, etc) it's like the above chart ... totally burned up in about 15", continues to accelerate to about 20". Another nifty side effect ... slower burning powder generate less chamber pressure than faster burning powders so it's a win /win situation ... higher velocity, lower chamber pressure.

Bill West, Sorry, I didn't mean to frighten you. Do you give tips on sporting events? Yes, here's a sports tip .... on game day, spend your money on beer and junk food. After the game you will be happy ... win or lose.
 

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. Do you give tips on sporting events? Yes, here's a sports tip .... on game day, spend your money on beer and junk food. After the game you will be happy ... win or lose.
EXCELLENT ADVISE,,,, as always. :D

I find this site helpful. You can click the caliber you want on the right , and bingo.
http://www.ballisticsbytheinch.com/357mag.html
BBTI - Ballistics by the Inch :: 9mm Luger Results

I think IMHO, the trick is choosing a weapon to meet your requirements. . They all take big jumps from 2 to 3 to 4 to 5 inches. But after 5 inches, the velocity "jump" slow way down on most calibers. . So if you want maximum sight radius, with the best velocity, and still want to have a sidearm you can carry. There is really no point going over a 5 or 6 inch barrel in most calibers. In my case, my hunting revolvers are ALL 5.5, 6.5, & (1) 7.5 Ruger revolvers. I want to shoot accurately @150 yards. I need the extra sight radius to do it, but I still want to have a reasonable pistol to carry. Once over about 6.5, your gaining very little. Its really not worth the trade. That chart really shows you where you should be looking for length, when you combine it with your requirements.

And as Iowegan stated, and as the charts show, Mostly ALL pistol calibers start slowing down between 16 and 18 inches.
 

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Here's the deal with sight radius. When you compute for 25 yards (900 inches) divide the sight radius by 900 and you will see how much the sights move to cause the point of impact to move 1". Example: let's say you have a 4" GP-100 with a 6" sight radius. 6/900=.0066" ... meaning for each .0066' you move the gun, your bullet will strike one inch off target. If you have a snubby revolver with a 2" barrel, it will have about a 4" sight radius. 4/900=.0044". A 6" barrel revolver will have about an 8" sight radius or 8/900=.0088" As you can see, a longer sight radius is more forgiving. In the above examples .... a 2" barrel versus a 6" barrel .... you can move the 6" barreled gun twice as much to get the same POI change at 25 yards. In other words, sight radius is very important with a short barrel when shooting at longer distances, however if you stay with design concepts (snubbies = close-in self defense), chances are you will never use the sights in a real self defense situation.

As in dcdixon's examples with muzzle velocity, after you get to a 5 or 6" sight radius in a handgun, there's not much of a practical advantage with longer barrels. So in my opinion, sight radius isn't all its cracked up to be. Rifles are a different story ... mostly because you will shoot at a much longer distance. My 22 LR CZ target rifle has a 24" barrel with a 20" sight radius. My Ruger 10/22 has an 18.5" barrel with a sight radius of 16". The reason .... you can hold a rifle a lot more steady than a handgun so you can actually take advantage of a long sight radius, whereas with a handgun, it's virtually impossible to hold it steady enough to take advantage of the longer sight radius. So .... there's a point of diminishing returns where extended sight radius probably won't improve your marksmanship. That said, there's a lot more important issues that affect accuracy more than sight radius.
 
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