Bullet velocity of a ported barrel

Bullet velocity of a ported barrel

This is a discussion on Bullet velocity of a ported barrel within the Defensive Ammunition & Ballistics forums, part of the Defensive Carry Discussions category; Looking at buying a new(Storm lake) barrel for my M&P compact. Standard length barrel is 3.58" in length. I could put in a 4.28'" length ...

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  1. #1
    Senior Member Array Sig35seven's Avatar
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    Jun 2010

    Bullet velocity of a ported barrel

    Looking at buying a new(Storm lake) barrel for my M&P compact.

    Standard length barrel is 3.58" in length. I could put in a 4.28'" length or 4.28" ported.

    It would seem to me that the longer barrel would increase bullet velocity but the ported barrel would allow the expanding gas to escape early and have little gain in velocity. Wouldn't I gain more velocity using the non-ported barrel of the same length (4.28")?

    Also, is there a way to determine the velocity gain when switching to the standard (non-ported) 4.28" barrel?
    I am using the 3.58" length in 357sig.

    Thanks for any help!
    "Confidence is food for the wise man but liquor for the fool"

  2. #2
    Senior Member Array JohnLeVick's Avatar
    Join Date
    Aug 2009
    Texas High Plains
    A ported barrel of the same length as a non-ported will usually lose some velocity. Simple physics: you bleed off some of the gas that drives the bullet before it's through driving it, and it will go slower. The effects are pretty variable, though. The bigger the ports, the greater the velocity loss. The closer the ports are to the chamber, the more velocity is lost. Hybrid ports lose the most. Now, if the ports are in an expansion chamber, like the Smith Power-Ports, the actual barrel length ends before the ports are reached, so that changes things. Speaking purely technically, such ports have no effect on velocity. FWIW, my experience with ported barrels, including factory-ported Glocks, Magna-Ported revolvers and autos, Power-Port Smiths, Hybra-ported revolvers and several others is that the ports do little to reduce muzzle flip or recoil UNLESS they are large and close to the chamber, like Hybrid ports, or on an expansion chamber, like on a Smith Power-Port or K-Comp.

    To my knowledge, there is no formula for determining just how much velocity will be lost by ports. Even if there was, there are too many variables to allow much accuracy. What are you trying to gain? If velocity increases are what you want, then you should go with the non-ported barrel. If it's muzzle flip reduction, then you want the ports. The .357 Sig has enough gas volume to make ports work some, but without an expansion chamber, you won't likely notice much reduction in muzzle rise.

  3. #3
    Senior Member Array adric22's Avatar
    Join Date
    May 2011
    Fort Worth, TX
    Not sure. My Glock 19c has a ported barrel. I didn't go out of my way to buy it that way, it was just the only Glock 19 they had in the gunstore back when I bought it. It shoots a V-shaped pattern of burning powder out the top of the gun. So I'm sure it loses some velocity that way. Heck, I'm not entirely sure what the purpose is. They say to limit recoil, but I'm not convinced.
    "Good people do not need laws to tell them to act responsibly, while bad people will find a way around the laws." -Plato


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