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reloading 357 sig

Discussion in 'Handloading and Reloading' started by pennsylvanian, Jan 14, 2020.

  1. pennsylvanian

    pennsylvanian Member

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    Hi, this is my first post. :)
    I've been reloading for rifle and also pistol, but I'd certainly not say that I'm a pro at it, by any means.
    I bought some Frontier CMJ .357" 125 grain bullets that I was going to load into my 357 magnum, but they look so close to the factory 357 Sig bullets, that I thought about loading them for this, even though they are .002" thicker. I wondered if the CMJ would make a difference. These also have a cannelure. Any recommendations for powder?
    I might just buy the jhp bullets that are made for the 357 sig.
     
  2. redbullitt

    redbullitt Member

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    357 sig takes .355 bullets, so honestly I'd just get the proper diameter ones. There would assuredly be a pressure increase, and 357 sig tends to be picky with bullet profile what with the bottleneck and all. How big of a pressure increase I can't say... they would likely chamber, but you'll be doing your own pressure testing in the dark without tools...

    Cast bullets like to be fat, like .002 or even .004 over sometimes, but jacketed does not play by the same rules. Plated can be a crapshoot based on how thick the plating is.

    Hodgdon has all the data you need on their site.

    General advise is to stick to the reloading data. What youre suggesting is definitely not that lol.
     
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  3. Middletown

    Middletown Member

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    I agree with redbullitt. .002 inch doesn't sound like a lot but for 357 Sig it probably is. 357 Sig is the hardest cartridge I ever reloaded for with proper neck tension the hardest thing to achieve. At least for me. I do like the idea of the cartridge.
     
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  4. fxvr5

    fxvr5 Member

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    Those bullets might be fine in the 357 Sig. Not all barrel makers follow the traditional party line for recommending which bullet diameter to use for the best results. Some recommend using oversize bullets to ensures a good gas seal and positive rifling engagement. Schuemann recommends a jacketed bullet of .001 to .002 inches larger, and lead bullets .002 to .003 inches larger for the best accuracy. Nowlin also suggests slightly oversize bullets.

    It can depends on several things, one is whether the loaded round with the slightly fatter bullet will still fit in the chamber.

    Just because a barrel is chambered for a .355" caliber cartridge, it doesn't mean the barrel's groove diameter is .355". Most are oversized. You can slug the barrel to find out. I've slugged about a dozen 9mm barrels, most are .356" or .357". Only one has been closer to .355" than .356". Lots of folks shoot .357 and .358 bullets in their 9mm barrels.

    SAAMI barrel dimensions for the 357 Magnum and 357 Sig are the same; .355 groove diameter and .346 bore diameter (+.004). That means anything between 0.355 to 0.359 is within spec. https://saami.org/wp-content/upload...FP-and-R-Approved-2015-12-14-Posting-Copy.pdf

    Same dimension for 9mm Luger and 38 Super and 380 Auto.

    Hornady shows three bullet diameters for their 38 Super data, .355, .356, .357".
     
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  5. pennsylvanian

    pennsylvanian Member

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    Thanks for the replies. I don't have to rush into this. I don't have the dies for this caliber yet. I'm going to load some of those projectiles in 357 mag and 38 first, and might see how one would fit in a 357 sig case, once sized and expanded. fxvr5, how do you slug a barrel?

    I took one of the projectiles and placed it flat nose down, into my conversion barrel, and not much of it dropped in, so it's probably closer to .355. I'm just amazed at how similar these are, to the factory loads that I compared them to.
     
  6. pennsylvanian

    pennsylvanian Member

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    Have you ever reloaded any bullets with a cannelure in this caliber?
     
  7. fxvr5

    fxvr5 Member

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    https://www.starlinebrass.com/articles/slugging-handgun-barrels-identifying-proper-bullet-size/
    https://www.meisterbullets.com/slugyourbarrelsdetails.asp

    you need an oversize bullet, or you can use a round ball like in the article(s). A oversize bullet should be a little bigger than .358 to .359". many lead bullets will be in that range.

    You can't tell from this.
     
  8. M1key

    M1key Member

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    I load it with some success using 124gr Hornady XTPs over 13.0 gr Accurate #9. I recommend getting a Lee factory crimp die to give a tighter grip. I prefer the Speer Gold Dot 125 gr however.

    M
     
    Last edited: Jan 17, 2020
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  9. Middletown

    Middletown Member

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    Short answer is no. I wasn't in love with the firearm I had in the caliber and traded it for something I liked much better. I remember loading 147 grain XTP's with AA#9 which fully filled the case and helped with bullet setback problem I was having using what I remember was Power Pistol.

    I bought the Lee Factory Crimp Die but traded the firearm before I reloaded any more ammo for it so never actually used it. Probably a good idea but no actual experience by me.
     
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