Barrel Length vs Power

[cirelaw]

Since 9mm is the standard, does a particular model i.e. carbine or P08 have greater velocity or force depending on the particular model. I ask this as last year I fired both models for the first time and my artillery seemed much more powerful at the range using the same Winchester 9mm! Was it a mere illusion? Eric

[Chickenthief]

Here is some calculated numbers using Quickload:

Bullet: Hornady 124gr FMJ RN
Powder: Unique 5.0grains
Calulated max pressure: 31.5kpsi with full burn in a 4" barrel.

4" barrel: 1141fps
5" barrel: 1196fps
6" barrel: 1238fps
7" barrel: 1270fps
8" barrel: 1296fps

So it seems that there are indeed more power in a 9mm from a longer barrel.
As you can see the gain for each inch is decreasing.

[Rick W.]

When I think of powders(relatively vintage anyway), when I think fast; I think of bullseye. Medium.....Unique. Slow as far as pistol type senerios, blue dot, 2400.

It takes time down a barrel for the slow burning powders to generate max stuff; burn completely(?).

In a longish barrel, bullseye can be out performed by 2400; as a crude example. Conversely, in a short barrel, bullseye may out perform 2400 as most of the slower burning powder does so outside of the barrel.

Just glittering generalities, lots of variables that get into the specifics of cartridge performance. Powders are coming on line all the time that have some interesting characteristics, but so little time to try them all.......

In reading these forums over the years, I have come to use Unique mostly in 6" or shorter barrels in my Lugers. I have used blue dot loads in longer(8"-14") with some relative success.

I think a medium to slow powder gives the Luger mechanism the time it needs to work super nicely, in my opinion. The fast powders, while efficient, are pretty quick in reaction time, which I think(?) is hard on the mechanism durability; again just opinion.

[ithacaartist]

Eric, this will make sense if you consider that the more energy put into the bullet, the more "power." In a longer barrel, the bullet stays in the barrel longer, to be pushed/accelerated by the pressure of ignition that extra bit of time, which is why the exiting round is faster than one from a shorter barrel. Henrik's data tells the story!

[sheepherder]

Originally Posted by Chickenthief

As you can see the gain for each inch is decreasing.

From your figures, I would say it is increasing...

[mrerick]

in effect, the longer the powder burn gasses expand into the barrel (which is effectively a piston sealed by the bullet until it leaves the barrel) the more the mass of the bullet will be accelerated.

Rich, the relative gain per inch decreases. Between 4 and 5 inches it increases velocity 55fps... Between 7 and 8 inches, only 16fps. This is because powder burned fast, and is not burning as the bullet reaches the longer barrel ends. A slower burning powder would accelerate things differently. The total generated gas pressure is also filling a longer and longer expanding volume until the bullet exits the barrel.

There are many things that impact this. The type (burning rate) and amount of powder, the bullet's gliding surface (including the material and it's bearing surface on the rifling) and the length and bore condition of the barrel itself.

All things being equal, the longer the barrel, the longer the gasses will push the bullet's base and accelerate it's mass. That will result in higher velocity. If the entire powder load has not burned by the time the bullet leaves the barrel, some of it will burn outside the barrel and not contribute to accelerating the bullet.

When you use a chronometer to measure bullet speed, you usually see quite a variation between individual cartridges built with the same components and powder load.

Bullet mass times velocity at impact becomes the amount of terminal ballistic energy that is delivered to the target.

- - - - -

Thinking all this further, is it any wonder that Daimler invented the internal combustion engine. It's like a barrel with a bullet that never leaves the party...

[Chickenthief]

Originally Posted by sheepherder

From your figures, I would say it is increasing...

Yes and do
Yes there is an inrease in speed but the growth/gain in speed dereases.

From 4" to 5" the gain is 1196fps-1141fps = 55 fps
5 to 6 = 42fps
6 to 7 = 32fps
7 to 8 = 26fps

So you see that each additional inch adds less speed to the total.
So the growth is decreasing ;-)

[sheepherder]

Ah, I get your point now. 2nd derivative.

[cirelaw]

First, I'm proud to be a group of firearm geniuses! Basically, the more spin and loads will directly add to result! I never even givin this so important factor a second of thought. A Kentucky rifle even without rifling the longer the better!

[DavidJayUden]

So why is longer better in a BP Kentucky rifle? Black powder turns to gas much more rapidly than does Smokeless, and has less pressure against the bullet further down the bore.
Is it for accuracy, IE sight radius?
dju

[cirelaw]

It was just a guess!!! A wrong guess! TKS

[G.T.]

When I was 12 years old, my dad gave me a .30 Luger artillery to shoot, and a bunch of ammo! All I can tell you is that thing was plenty snotty and shot like a laser! I will have another some day God willing... GT...

[cirelaw]

G.T. I'm envious!!

[DavidJayUden]

Now there's a slice of real Americana, send a 12 year old out with a pistol and a bunch of ammo, tell them not to come home until it's all gone.
In my younger days my parents would drop me off at a nearby prairie dog town with a .22 and a brick of hollow points. They'd come back much later in the day, load me up and I'd sleep all the way home. Good times.
dju

[G.T.]

When I wasn't shooting the Luger, I had a Ruger 10/22 open sight Sporter, (first year!) on a sling around my neck on a Harley Davidson M50 (girls model step thru) going right down the center of the railroad tracks shooting gophers that dared to show themselves....... God it was fun! Many a gopher was the victim of ricochet!!! Rifle rocked!!! trigger pull was horrendous!!! I was a knot head... it was perfect! til....lat'r...GT....

[rhuff]

We had a prairie dog town about 2 miles out of town. On Sunday, my dad would load up the three boys and our .22 guns and out we would go. We shot from out of the car windows, or got out and shot across the hood. I question how many we really hit as none we close shots, but we thought we hit a lot of them.

One can't go home again, but I sure wish that I could every now and again.

[Rick W.]

When I was young and on the farm, Dad would load up 22 shorts in a Remington 550, and hand it to me. I was not allowed 22lrs, they were too powerful.... ......but he made sure I knew how to handle and respect firearms, before giving me a pass.

As I got older to be able to look out the front picture window, my uncle Ed would come over to hunt quail with his brothers. All had Browning A5's, mostly 20's; uncle Ed's was a sweet 16. At the end of the day, uncle Ed would sit me down with the 16 and teach me how to care for it.................gosh, I loved that back then and even now; nothing like a fine firearm and knowledgeable, loving folks.

My Uncle Dutch hunted with a 28 gauge; nope, not a Browning; he was a little bit of a maverick. Mom told me I am a little like Uncle Dutch, he always had a fast car; guess for now my blue devil is fast enough for me............but one can never have enough horsepower you know....... .

fond times, mighty generous of folks to relate such.

[cirelaw]

God Bless~

[wlyon]

I started hunting and shooting with my Dad in 1948. WW2 was over and ammo available again. Great memories of another time. Bill

[cirelaw]

A Norman Rockwell Moment!!