Barrel ports and how they affect velocity

[Polar Express]

Hi All,

Generally accepting that the length of a barrel will have a significant affect on the energy of the bullet, (longer bbl= higher energy)...

If someone puts a port in a barrel (say to reduce muzzle rise from recoil) how much energy will be lost?

To clarify my question here is a more specific example:
Lets say I have a 6" bbl, and a qualified person puts proper ports in the barrel (for sake of example only) exactly 1/2" and 3/4" from the muzzle, would that mean that the performance of the EXACT same load would perform similar to an unported barrel that is 5.25"? (the location of the first port).

OR.. would it perform similar to an un-ported 6" bbl?
OR... would it split the difference, or be in the middle but closer to one length or the other?

I sure hope the word choice in my question is clear, I know what I'm trying to ask, but I'm slightly afraid I may not be communicating it clearly.

Thanks in advance,
PE

 

[Snyper]

Go to "ballistics by the inch" to see the difference losing an inch of barrel makes, and I think you'll see the effect of having a few holes in the barrel is hardly noticeable.

http://ballisticsbytheinch.com/

 

[243winxb]

Mag-Na-Port

Little velocity is lost. If shooting lead bullets, some of the lead will form around the ports. Hoppe's number 9 easly removers it. The red insert will become dark gray. There will be more noise. Accuracy is still good as before. If you shoot a 44 mag at full power, double action, you will want the Mag-Na-Porting.

[/URL][/IMG] I have seen/heard guns when the porting is just a series of holes drilled into the barrel. Makes to much noise and doesnt work as well. IMO.

 

[Polar Express]

I went to BBTI, I've seen that site before, and it's very interesting. The data those fellas put together is pretty cool.

I hunted around BBTI, and was unable to find where it addressed ports in a barrel. It certainly could have been right in front of me, but I did look, at LOTS of pages there, and I didn't see anything.

If a LITTLE velocity is lost, I'm just fine with that. It tells me, that if I were to go for a bit longer, ported bbl, I'd be looking at better performance and have a little help from the ports with follow up shots, helping (at least a little) with muzzle flip.

The dirtyness, I don't give a hoot about, I clean my guns, and for the purpose this is for, it'll get cleaned often.

Thanks,
PE

 

[Jim K]

BBTI shows the difference in velocity for each inch of barrel. So if you have a caliber/load with a 6 inch barrel that gives 1300 fps, and a 5 inch that gives 1230 fps, you have 70 fps loss with just cutting the barrel. Since slotting the barrel for ports will reduce the velocity less than cutting it, you could probably say that porting the 6 barrel will reduce velocity by 30-40 fps or less, not a significant velocity loss.

The question is whether your better shooting with less recoil is worth that relatively small velocity loss. That is your decision.

Jim

 

[Polar Express]

Jim K,

Thank you! That is the more definitive answer to my question: approx 30-40 fps, (or less), all other things being equal.

PE