Many years after trading away my Taurus "Brazilian Beretta", because I was only interested in "carry guns", I have a S+W 915 on the way. (It was more my general interest in 3rd gen Smiths than my want or need for a "duty-size" or "hi-cap" gun.)

Anyway, the original crop of "wondernines" all featured slightly longer barrels than the Smiths, even though most other measurements of size, weight and capacity were very similar. The Sig 226- 4.4"; CZ75- 4.7"; Beretta92- 4.9"; Glock 17- 4.49" and even the "Original Wondernine", the BHP has 4.5". Leads me to my 2 questions:

1- Do any of you historians know why the (only) 4" barrel? Was it perhaps due to long history of the "standard" 4-inch revolver?
2- How much benefit to accuracy and velocity does a 1/2" make? I'm more interested in the difference between my S+W compacts with 3.5" vs. the 4" than I am the Smith's 4" vs. the others' 4.5"+.

Thanks, all!

I don't know this for certain, but I suspect S&W's use of the 4" barrel in the third generation guns reaches all the way back to their original 9mm pistol which eventually became known as the model 39. This decision allowed all the full-size holster- carried 9mm's to use the same barrel. In fact, until the advent oh the 69 series pistols circa 1987, I don't think they offered another barrel length for their 9mm's. As to why that barrel length was originally selected in the late 1940's; most likely it made a nice, well balanced firearm (which is absolutely the case with the M-39). If memory serves, both the original Luger and the P-38 had 4" barrels, so S&W was just following suit (I am by no means an authority on Lugers and Walthers, so if I'm wrong about the barrel lengths, don't flame me too badly). I will also add that, although modest gains in velocity are realized in longer pistol barrels (carbines and SMG's notwithstanding), the 9mm pretty well reaches its ballistic potential in a 4" tube.

HRF

Congrats on getting your 915!! Superb, very underated pistol.

I doubt the 1/2" difference in barrel would amount to 50 FPS using factory ammo.

My 915 is a tack driver. Using Ranger ammunition I'm confident in its ability to get the job done with a 4" barrel. Enjoy your 915!! Regards 18DAI.

18DAI;
I researched the 915 as best I could and your comments popped up everywhere. I hope I am as happy with mine as you are with yours. Through this and other forums I only saw 1 or 2 negative comments about the 915. I've become quite a fan of the 3rd gen 9's and am bringing this one home for a tad under $225. Couldn't really pass it up at that price.

BUT I started this thread generally speaking about the 4" barrels. Interesting comment from Sharpshooter about the 9mm "reaching its ballistic potential" from a 4" barrel. It just seemed kind of curious to me. All the autos I mentioned were basically developed in the same era. I think the S+W's barrel at 4" is the shortest of any "full-size" gun in their class. We had years of many years of 5" 1911's as standard service weapons and we've had quite a few now of the M9's almost 5" tube. It just had me wondering why S+W stuck with the shorter one.

I believe it had more to do with the military interest in a smaller, lighter 9mm handgun after WWII to replace the 5 inch 1911 .45 Auto. Although the military did not go through with replacing the 5 inch 1911 .45, realizing it had plenty of them in stock, the public and the police got the benefit of the commercial release of the Commander from Colt and the Model 39 from S&W.

The pistols developed pursuant to the military's wish list at the time were the Colt Commander in 9mm, which had a 4 1/4 inch barrel, and the S&W Models 39 and 44, which had 4 inch barrels. The 39 was the survivor in the S&W catalog, and is a so-called traditional double action and the Model 44, of which very few were made, is a single action.

Once S&W had the 39 in place, it was pretty well discovered that it could do double duty as a uniform pistol and an off-duty pistol, and the Illinois State Police, who first adopted the Model 39, at least on a large scale, did exactly that, using the issue pistol for both uniform, plain clothes and off-duty.

It is difficult to find a better feeling, better balanced 9mm than the S&W 39s.

There is a perception out there that a longer slide and barrel (which creates a long sight radius) makes a gun more accurate. This is of course not always true but has definitely permeated the gun market. 3-3.5" barrel for concealment, 4-4.5" for duty and 5" for tactical or competition. It seems every manufacturer has to make a long slide version of their guns, even S&W made a 5" 9mm performance gun. But like Sharpshooter said, the 4" barrel is really all you need in 9mm.

It is not a perception, it is a mathematical reality. If you have two identical firearms and there is not a mechanical deficiency in either, a longer sight radius will be more accurate due to simple math. Any error in placing the post exactly in the center of the post is magnified by a shorter distance between the sights. It sounds small but it doesn't take much angular error over the distances we shoot to see the error. That doesn't mean short barreled guns are inaccurate by any means but they will show aiming errors to a greater extent than a longer sighting radius. Pretending that this sighting induced error doesn't exist doesn't make it true.

This is of course a discussion of absolutes and the skill of the person behind the trigger will make this "difference" moot in most cases. Snubbies are mechanically just as accurate as a six inch barrel, that sight radius just magnifies any error that you put in. The exact same error over a longer sight radius simply is magnified smaller less because the angles are less.

Back to the original thread, I got to say I have no idea why they use 4" barrels. My Beretta Cougars are more like 3.5 and I always wondered the same thing.

One man's reality is apparently another man's perception. Your explanation claims sighting errors, which is a human factor and not a gun factor (which you did mention). A 3.5" auto in a ransom rest will prove equally accurate as an identical but 4.5" auto in a ransom rest. I watched a skilled shooter put 5 out of 5 rounds into a man size target at 75 yards with a 1 7/8" snub nosed revolver (S&W 638). I have also watched people spray holes all over targets (emphasize all over) with long slide Glocks at 10 yards. Again, human factor. And for some reason the math never helped either of them shoot better.

Exactly. Mechanically a 3 inch tube is just as accurate as a 6 inch tube. The only gun factor that makes the longer gun more accurate (all else being equal) is the longer sight radius. The reason people shoot the longer ones better is MATH. Examples of people shooting more accurately with shorter guns doesn't prove anything. If you test two identical guns with the only variable being sighting planes, then your argument would hold water. You can argue all day and I will take math and science over your feelings all day. If you want to take a Ransom rest shooting everywhere you go then you will in fact never shoot a longer handgun better or worse than a shorter one. But, since most of us actually use those funny little bumps on top of the slide and induce visual error (unless you have some magical skill the rest of us don't) the visual error is magnified (mathematical fact) the shorter the distance between the two sighting planes. It is not the mechanics of the gun but to argue that all else being equal the longer handgun won't be more accurate (nothing to do with the gun, everything to do with the sighting error) is nonsensical.

I have plenty of shorter guns that I shoot better than longer guns. That is anecdotal and doesn't prove anything. Two identical guns the one with the longer sighting plane will have less induced sighter error and your groups WILL be tighter. Put a scope on the shorter and erase the optical error and then this argument is moot, but over sights you can never overlook this as a factor in shooting. Sorry if the science (or me pointing it out) annoys you. It still is true.

Here is a reasonable example. Take a skilled bullseye shooter, not some bumpkin "spraying holes" all over the place and give him two identical smiths, one with a three inch tube and one an eight inch tube. He will be plenty accurate with both, mechanically the two will shoot hole for hole with each other at 25 yards. But, since he has to use the sights on the gun, he has an error induced, over the course of fire the error will be bigger with the smaller sighting plane. Once again, I agree it is not because the GUN is more or less accurate but because the shooter HAS to use the sights and so an error (bigger or smaller depending on the sight plane length) WILL by definition be introduced. This is not mere musings on my part. This is all hard science, the same kind that sends a rocket TO the moon not just NEAR the moon.

And yet both of your posts about math and science have done nothing but validate my point which was (and is); "There is a perception out there that a longer slide and barrel (which creates a long sight radius) makes a gun more accurate. This is of course not always true."

In the words of Plato: "Science is nothing but perception".

A longer barrel and slide by definition makes a longer sight radius. A longer sight radius makes ANY gun capable of more accuracy. I wont argue semantics.

This is your quote:

"There is a perception out there that a longer slide and barrel (which creates a long sight radius) makes a gun more accurate. This is of course not always true."

Two theoretically identical guns, one with a longer sight radius will ALWAYS (if sight radius is the only difference, identical guns remember, take away all other factors) outshoot the shorter one because a human being is behind the sights and has to aim the weapon. You will induce larger errors with the shorter sighting plane. That is not perception, that is reality, even Plato would agree with this. There is always error and as the distance shortens the error magnifies. Can you find shorter guns that are more accurate than longer guns, can you find guns that individuals shoot better than others regardless of length? Of course, but that is the difference between anecdotal and empirical (you quoted Plato after all!) All else being equal (that is the critical component here) ANYONE will shoot smaller groups with a longer sight radius and to act like this isn't a valid factor (while telling tales of idiots with long slide Glocks, as an aside, I love my long slide Glock) does not do anyone justice. That is all I am saying. If your spouse/buddy/family member merely wanted to shoot tighter groups on paper, no ccw/competition/duty/etc. and they found the firearm that fit them perfectly and it came in differing barrel lengths, steering them to a shorter tube would be a disservice. We pick different barrel lengths because of necessity, but longer (as else being equal) will lead to tighter groups. Of course, without training or knowledge the longest slide in the world makes a very good hammer.