What effect does porting have on bullet velocity?

C

C0untZer0

Moderator
For porting like the EFK Firedragon does the bullet lose velocity as it goes past the porting?

attachment.php


I want a little longer barrel for my 17L, and the EFK Firedragon has a longer barrel, but if a bullet loses velocity as it goes past the porting, it seems like a moot point. I don't want a longer barrel for the sake of a longer barrel, and the recoil is already so mild I don't think the porting provides a benefit for recoil reduction.


attachment.php
 

Attachments

  • EFK.jpg
    EFK.jpg
    9.1 KB · Views: 569
  • EFK2.jpg
    EFK2.jpg
    71.3 KB · Views: 568
The velocity goes down some in response to losing gas out of the porting, and not completing its journey to the muzzle. The only way to tell is to test with the two indentical barrels, one ported, one not; then chronographing to test for the difference.

You can tell that some of the powder expansion is wasted when you see the flash coming from the ports.
 
Over the years there have been lots of tests on this subject and the loss is fairly insignificant. The numbers I remember were something a 25 to 35 FPS loss. I wouldn't sweat that at all. If you want or need the porting, go for it. As previously stated when you start seeing flames you're going as fast as you need to. Any more is just for show.
 
OK, so I've heard that you gain approximately 20fps for each additional inch in barrel length (not to infinity - we're talking a difference of 7" v 6"). So if you lose approximately 25fps with the porting, a bullet coming out of a 6" non-ported barrel is going to be going about the same speed as a bullet from a 7" ported barrel.

Does that sound right?
 
Countzero:
I'm not sure how much velocity that I lose with my ported Smith Wesson Model 29 and my ported Super Black Hawk. The Black Hawk's barrell has been shorteded to 4 5/8 inches. Although they recoil less, they are stil a handfull. When the bullets hit the 100 yard steel targets the targets jump violently. The laws of physics dictate that some velocity will be lost with a ported barrel. How much velocity is lost must by determined by a chronograph.



Semper Fi.

Gunnery sergeant
Clifford L. Hughes
USMC Retired
 
OK, so I've heard that you gain approximately 20fps for each additional inch in barrel length (not to infinity - we're talking a difference of 7" v 6").
Click to expand...

You gain a lot more than that per inch with standard pistol barrel lengths. More like 50 to 75 FPS gained on average per additional inch of barrel length.
 
Velocity loss due to shorter barrels is not a straight forward prediction. There are many variables. Just one example from ballisticsbytheinch.com shows anywhere from a 4 fps to a 81 fps loss for one inch of barrel length reduction.

velocity_loss_by_the_inch.jpg

It makes sense that there is a greater per inch loss when that inch represents a greater percentage of the barrel length.

C0untZer0

What effect does porting have on bullet velocity?
For porting like the EFK Firedragon does the bullet lose velocity as it goes past the porting?
Click to expand...
The effect would be to lower bullet velocity by allowing pressure to escape before the bullet exits the muzzle.
 
Barrels for the 17L

The LoneWolf threaded barrel is 6.56"

The EFK Firedragon ported barrel is 7.00"

So what I'm thinking is whatever velocity I am gaining with the additional .44" I'm losing due to the porting.

I don't need recoil reduction, I just would like higher velocity.
 
...the recoil is already so mild I don't think the porting provides a benefit for recoil reduction.
Click to expand...

If you're seriously shooting for accuracy, the reduction in perceived recoil can be significant. Lots of .22 long rifle match pistols are ported for that very reason.

The biggest draw-back to porting I've ever encountered is the extra time it takes to clean the ports: up to two minutes per barrel. Actually, there's a second draw-back: more noise directed toward the shooter. If your hearing is as bad as mine, you may not notice it, but I'll recommend wearing both custom-made plugs and muffs.
 
I can say that you definately wouldn't lose any velocity with the KKM barrel pictured over the standard barrel. The KKM is longer than the standard before the bullet meet ports. With a barrel of equal length though you will lose some velocity.

The amount isn't just dependent on barrel it also has a lot to do with the load.
 
I wouldn't worry about any lost velocity. If any at all, it would be minimal. I think a lot of people just over analyze this. Trust me. Your target isn't going to outrun your bullet.;)
 
Count-
I believe your reasoning is correct. There will not be much velocity difference.
Those ported barrels were made without ports before the cuts were made. Why not contact the maker and see if they would sell an unported one?
 
for an after the fact opinion you should have checked the velocity before the barrel was ported and then compared after it was ported. I doubt that you will notice any difference in velocity.
 
my turn

Just because a barrel is longer does not automatically give it 'higher velocity'.
It is assumed that greater length will increase velocity. Actual testing will determine the reality.

Without actual testing we can only assume; test to know.



"Geez, Tim, why the negative attitude?"
"I'm not negative, I've just spent enough time chronographing numerous guns to know not to assume."
 
You must log in or register to reply here.
Back
Top