How much energy is lost with...

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10-Ring

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How much engery is lost with...

When shooting a shorter barreled gun that has been ported, how much energy have you really lost? 10%, 25%, 50%...more?
 
I don't think a general answer is possible on a % basis. I was informally told that by having my Taurus 445 2" snubbie ported I was giving up ~50 fps muzzle velocity but I bet the guy that told me that took a SWAG (scientific wild a** guess). Trouble is, for the 180 grain Hornady loads I usually carry is this 50 out of 1000 or 50 out of 750 (for a .44 S&W special most published mv's are for 5-1/2" bbl or longer). This would amount to (950/1000)^2 = 0.9025 or 9.75% for one and (700/750)^2=0.8711 or 12.9% for the other. I sure hope someone has chronograph data to share because it's a good question I would like a concrete answer to.
 
It can't be anything significant in a rifle or shotgun because the bullet has reached very close to max velocity by the time it gets to the ports and the ports release only some of the pressure . The operation of porting is that at the instant the bullet leaves the barrel the barrel is filled with still expanding gas, that then creates in effect a rocket. That rocket effect is responsible for about 25 % of the recoil. If we release those expanding gases just before the bullet leaves the barrel we then have reduced the recoil and if the ports are on top of the barrel we have reduced muzzle rise. For a 2" snubbie perhaps 5 % ? In a revolver the loss from the barrel and cylinder gap should be no more than That.
 
This is one of the biggest reasons that I won't own a ported snub.

I am already giving up so much velocity by having a short barrel that I don't want to give up ANY more with ports.

Ports don't help with recoil they help with muzzle rise. And they don't help as much with shorter barrels as they do with longer ones.

For less recoil I prefer an all steel snub. The don't weigh THAT much.
 
A "rule of thumb" for pistols is about 50 FPS per inch of barrel, so if the ammo specs are 900 FPS from a 5" barrel, you'll get maybe 750 FPS from a 2" barrel. Energy is, of course, a direct function of velocity.

However like any "rule of thumb," it's no better than using your thumb for a ruler....
 
Two added comments: I bought my ported Taurus 445 2" bbl in .44 special AFTER I fired a non-ported gun: the porting does really help reduce tendency to flip up and the stress on the web of my right hand. There is an upward fireball that is not too bad for the 180 grain Hornady ammunition but can get pretty intense with my Unique 200 grain handloads. You would never want to shoot this gun from the waist or you would have it spray gas and particles in your face. I guess like life, choice of what you shoot is a compromise. That's why one gun won't fit all.
 
Leaving aside percentage figures ....I do reckon that biggest losses occur with hot loads and slow powders ... the faster powders that can be used with lighter loads will IMO be more efficient ... the speed of gas production will mean a faster ''shove'' on the bullet to achieve faster acceleration in the short time the gases are confined ... a lot is wasted for sure with slower powders . thus the fireball!!
 
The latest issue of American Rifleman had something on this, minus the porting and in a revolver, I do believe. And it was specifically for .44 mag. So as un-related as it seems at first, it gives a good idea of the velocity (and energy) loss per inch of barrel loss. FYI, the started with an 18 inch barrel and removed one inch for each test, down to 1 inch total.

Take a look at it to get an idea of how barrel length affects velocity and muzzle energy.

It didn't discuss porting, but I don't think porting affects it as much as barrel length does. Course, I don't have any numbers to back that up.
 
There is ONE golden rule here, and that is:

Each gun is an individual.

There, that is all there is to it. You can chronograph 5 IDENTICAL revolvers and have a spread of 20%. Pistols are less spread than revolvers but still very much individuals.

Some snubbies will be as fast of faster than 4" guns. Some 4" guns will be faster than 8" guns. Some snubbies are pathetically slow as are some long barreled guns.

There is ONE way to find out what your particular gun is like, and that is to shoot it over the chronograph. Until you do that you might as well be reading chicken bones to get your answer.
 
American Rilfeman Data

Table for Velocity Vs Barrel length for a 44mag revolver (From Page 28 of the December 2003 Issue)

Length (in) velocity (fps @15ft)
1 742
2 935
3 1067
4 1165
5 1239
6 1298
7 1345
8 1384
9 1417
10 1445
11 1469
12 1490
13 1508
14 1525
15 1539
16 1552
17 1564
18 1575

Delta v goes from 11 fps at the 18" end down to 193 fps for the jump from a 1" to a 2"

Not linear; my guess would be that as you get somewhere up in the 10" range you've burned all the powder for the round they used (240 grain factory loads)

As mentioned above (chicken bones et al) your mileage may vary.
 
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