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Forensics question: 9mm vs 357SIG

Discussion in 'Caliber Corner' started by Henry's Dad, Jun 16, 2012.

  1. Henry's Dad

    Henry's Dad woof, woof

    Here's a question that's been on my mind lately:

    If a forensics team extracted a slug from a shooting victim, or a wall, or ballistic gelatin, etc., and the slug remained intact, how would they be able to tell if it came from a 9mm or a 357SIG firearm?
  2. dkf


    Aug 6, 2010
    Usually the .357sig bullets are slightly different than 9mm bullets. They could also get some idea of how fast the bullet is going but the expansion, damage and etc. If you load the exact same 9mm bullet into a .357sig and load it to 9mm velocities they are never going to be able to tell the difference. Well unless you leave the spent case at the scene.:supergrin: IMO I think some of these forensic ballistics people flatter themselves a little too much as to how reliable the data collected from only a bullet is. Primarily when it comes to tool marks.
    Last edited: Jun 16, 2012

  3. Decguns


    Dec 29, 2003
    Your standard 9MM has a rifling twist of 1 - 9.84. The 357 Sig has a standard 1 - 16 twist. A lot of 9MM after market barrels are 1-16, though.

    Pick up a handful of projo's from your range's backstop, and you can tell the difference between the two rifling twists.
  4. Henry's Dad

    Henry's Dad woof, woof

    I thought rifling might be the easiest way to tell the difference, but Glock seems to use the same rate of twist in the 17 and 32. And as you mentioned, many 9mm barrels may be 1 in 16.

    So, discounting twist rate and assuming "standard" 9mm bullets were loaded in the 357SIG, how else might one determine if a slug was fired from a 9mm or 357SIG?

    If it had a 1 in 9.84, you could say it was a 9mm. But if it was 1 in 16, you couldn't say definitively, as it might be either.

    I'm just wondering about this from a CSI perspective. What would the forensics people look for in order to tell the detectives, "hey, your shooter used a 9mm (or 357SIG)."
  5. cowboy1964


    Sep 4, 2009
    What the other guy said, unless you recover the bullet or the case it would just be a guess thought they may get a general clue from the side of the entry hole.
    Last edited: Jun 18, 2012
  6. Ljutic


    Jun 8, 2011
    Wouldn't the same question exist for the .38 Super?
  7. dkf


    Aug 6, 2010
    Pretty much. You could add the 9x25 to that list as well.
  8. unit1069


    Oct 10, 2007
    So. Central US
    I think the question in your example would be whether forensics could tell if the bullet was fired from a .38 Special or .357 Magnum.
  9. larry_minn

    larry_minn Silver Member Millennium Member

    Dec 16, 1999
    They would just pick up fired brass, read headstamp and ......

    :) Someone had to say it.
  10. unit1069


    Oct 10, 2007
    So. Central US
    But if the shooter(s) didn't leave the brass at the scene how does forensics determine the caliber?
  11. Tiro Fijo

    Tiro Fijo

    May 31, 2011

    First of all, CSI is total BS. :upeyes: The real answer would be:

    "Sorry fellas, the lab is backed up for 6 mos. due to budget cuts. What's that? Rate of twist? Whadda we look like, NASA?"


    If you want to know how murders are solved in the REAL World then watch The First 48. It's the most depressing show on TV as it really shows you how the other half "exists".
  12. unit1069


    Oct 10, 2007
    So. Central US
    The First 48 is one of my favorite shows, although it's true that it's very depressing.

    Last night an episode featured three very young men (all teenagers, I believe) and two of them had no prior records of any kind. They decided to call another teenager for some marijuana and planned on murdering him beforehand.

    The victim picked up a friend of his and both of them were murdered for a small amount of weed and $200. Not only are two young men dead for a piddling amount but three other young lives are completely down the drain. One has to wonder how some young people get so caught up in the gangsta image that they completely lose sight of reality.

    It's astounding to me that a number of young people are without any moral compass or sense of values. More alarming is that we interact with a good many of them on any given day.
  13. fredj338


    Dec 22, 2004
    I doubt they could tell. I have been to a couple autopsies, spoken w/ the examniers. Unless you find something unique about the bullet, an expanded bullet isn't telling you much about the specifc case it was fired from. ACtual caliber is easy if enough bullet is left to measure, which cartridge was used, is almost always determined by finding a case.
    Last edited: Jun 17, 2012
  14. PghJim


    Apr 21, 2005
    You cannot tell for sure, but you could make some assumption. I think only Glock uses the faster rate for both 9mm and 357, or at least the number is low. I would say if the rifling has land and groves and has a fast rate of twist, it would be a 9mm. This all discounts after market barrels. BarSto uses 1 in 16 for their 9mm also. So if it had a slow twist, you would not know.
  15. Ben B

    Ben B

    Feb 28, 2012
    I was wondering kind of the same thing with conversion barrels. like a 23 can use a 32 or a 9mm conversion barrel. I never figured how the would now a 23 was used to commit a crime if a 32 barrel was used.
  16. Adamz04


    Mar 28, 2012
    I think this question only is relevant if you are a criminal. If it was a justified shoot and you had to go to court your gun would be evidence so they would know what you were shooting.
  17. banger


    Nov 8, 2005
    Where evil lives

    Sorry to say but, I think you have somewhat of a distorted view of what forensics actually says.

    Absent some unique bullet style, a forensics report would read that the projectile in question recovered at the scene is approx. .355 in in diameter, weighing approx. 125, and a construction that would be consistent with ammunition manufactured by----(insert brand here),

    The report would then indicate that rifling marks on the bullet revealed X number of rifling marks, right or left handed twist, conventional or polygonal bore.

    The report would then conclude that the weapon in question is likely a (example) Glock type pistol of medium caliber consistent with a 9mm weapon, but also consistent with .357 Sig caliber and maybe even a .380 caliber (on the assumption that the bullet in question is a style loaded in both calibers).

    The forensics reports you are citing exist...on television, not real life.

    T.V. is great, I once watched CSI (Las Vegas) get finger prints off ......ready....a BRICK!

    Let a real techno-weenie do that and they'll present him with a Ph.D..
    Last edited: Jun 19, 2012
  18. Fletcher D

    Fletcher D

    Apr 20, 2011
    The projectile in a 357sig is not the same projectile as a 9mm parabellum. It's the shape and size of a .38 or .357magnum. The 9mm is ever-so-slightly narrower and has much more of a point.

    Andy D
  19. banger


    Nov 8, 2005
    Where evil lives