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Velocity differences, 4.5" v. 5.2" 357SIG barrels

Discussion in 'Reloading' started by jeffreybehr, Oct 9, 2011.

  1. jeffreybehr

    jeffreybehr Silver Member

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    Bought a StormLake 5.2" barrel for my 31G4.
    [​IMG]

    Chronografed 2 loads today thru this barrel and the original 4.5"er. CED chrono, 1st screen at 10', about 80dF, all samples 10 rounds. Cartridge OAL 1.135" to 1.140".

    PD load--125g. Barnes all-copper TAC-XPs--
    4.5", 1359FPS, SD 12.5
    5.2", 1365FPS, SD 9.0 ... < corrected
    This load uses 9.2g. [each load weighed] HS-6, the overall-best powder I found with this long bullet, WSPs, and Speer nickel cases.

    Practice load using new (to me, at least) Montana Gold 125g. HPs--
    4.5" barrel, 1364FPS, SD 7.0
    5.2" barrel, 1373FPS, SD 17.9
    This load uses 8.5g. 800X, WSP, Speer nickel cases. 800X is a course, large-flake powder which does NOT dispense evenly from the mechanical powder measure I use for my practice rounds.

    I'm surprised at the small differences; I expected something more like 20 - 30FPS. The SL barrel is nicely machined and fits a little tighter in the slide. I think the chamber is slightly smaller than that in the original Glock barrel; my former PD load won't chamber in it.
     
    Last edited: Oct 10, 2011
  2. fredj338

    fredj338

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    Every gun/bbl is diff, not unsual at all.
     

  3. bansheex

    bansheex

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    I have the same gun, stock glock 357sig barrel, and am getting ready to reload. It looks like the HS-6 worked pretty good for you. I plan on using the Montana Gold 125gr JHP because it's a truncated bullet like your using. Anything else to look out for?

    Don
     
  4. dkf

    dkf

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    Any pics of the new MG 125gr. JHP? MG doesn't have pics on their site.
     
  5. Brian Lee

    Brian Lee Drop those nuts

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    I have a G20 so I've been able to compare velocities from stock 4.6" barrels to 6" ones. Even then, the difference is never more than 75 or 80 FPS, and that is often within the variation I get from one round to the next anyway, using factory ammo.

    When I first got my chrono, I was only mildly put off by the fact that my 6" barrels didn't give me the velocity boost I hoped for. What REALLY ticked me off was discovering that so many ammo companies LIE about their velocities, (some more than others - by a LOT) and also how inconsistent the velocities are. IMO, factory ammo that gives 80 FPS differences from one round to the next OUT OF THE SAME BOX, is CRAP. It's also proof that any reasonably careful person can make reloads of much higher quality than what you typically buy new at a store.
     
  6. Colorado4Wheel

    Colorado4Wheel

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    G20 has a too light of recoil spring. So it opens to fast and can have erratic FPS as a result. I got a heavier spring and it tightened up the ES/SD a lot. But I hated the way it felt so I went back to the stock spring. Below a certain threshold you don't see it but above 1100FPS with 180 gr bullets.it does make a difference.
     
  7. Brian Lee

    Brian Lee Drop those nuts

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    This is very true and I forgot to mention it. I get the same result as well, beginning at about the same power level.

    A 20 or 22 pound spring helps a lot with velocity spread when using full power ammo in a G20, (Thanks to Tim on the Buffalo Bore website for his tech article on that!) but in my remarks I should have mentioned that I already replaced the spring, and still found way too much spread in the velocities of certain brands of ammo that I had once been a big fan of, so I really think ammo quality is often the reason.

    I guess my real point is that having your own chrono can drastically alter your opinion of who makes good ammo, and who makes over-priced crap. In my case, I'm no longer the self-appointed fan club president of a certain "crap maker" who I no longer buy from. I used to be all Ga Ga over their velocity lies, until I realized how much of it was just lies.
     
  8. PEC-Memphis

    PEC-Memphis Scottish Member

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    Doh ?
    Some have reported that all other things being equal, the polygonal rifling produces a better gas seal than conventional rifling. Some IDPA shooters had to slightly increase their powder charge when using conventionally rifled aftermarket barrels to make PF. You may have picked up a little velocity by using the longer barrel, but lost some due to the rifling.
     
  9. fredj338

    fredj338

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    The poly rifling in the Glock can produce a slight vel increase, again, every gun is diff & it seems to vary w/ caliber. I bought a LW bbl for my G17, vel are almost identical, well within the margin of vel variation one normally gets from any ammo, 20-30fps. The poly rifling does seem to give slightly higher vel in my G32 vs my USP, but it's always going to vary & a chrono is the only way to KNOW what your ammo & gun is doing.
    I am not so sure it's a lie vs they cherry pick their best vel runs. Your gun/test platform is not theirs, so you can't realisticly expect identical vel. It's been like this for decades w/ ammo manuf. Even handloaders w/o a chrono will tell you their ammo does this or that based on a reloading manual's numbers. It just isn't reallity. A chronograph is a sobering tool for any handloader.:whistling:
     
    Last edited: Oct 10, 2011
  10. jeffreybehr

    jeffreybehr Silver Member

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    I believe this is an MG bullet; I bought them from Rocky Mntn Reloading, and I think Jake is already out of them.
    [​IMG]
    Pictured with the Barnes TAC-XP, the only other loose bullet I possess.
     
  11. dkf

    dkf

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    Thank you sir.:wavey:
     
    Last edited: Oct 11, 2011
  12. Neal

    Neal Millennium Member

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    Just for comparison, back in the days when I was shooting and chronographing ProLoad 357 SIG ammo (125 gr jhp), I got an average of about 1500 fps with my KKM 4.4" barrel in my Glock 23. The same ammo chronoed 1570 fps out of my KKM 5.3" Glock 35 barrel.
     
    Last edited: Oct 15, 2011