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Thread: Any breathing room with OAL in 40 S&W

  1. #1

    Default Any breathing room with OAL in 40 S&W

    Setup my rig for 40's last night and I had some trouble. In general I have 10-15 rounds that are 1.136-1.145 when the OAL should be 1.135

    Is this variation acceptable? If there is even a remote chance that it's not I'll get rid of them but I was just curious if there is any room for error in length with the 40..

    What are the rules for OAL with pistol rounds if there even is any?

  2. #2
    Member AKDoug's Avatar
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    The biggest issue is feeding, then pressure. I honestly don't think that .01" is going to cause an issue, especially since it's on the long side, not the short side.

    The 1.135 length was set in the days of .40S&W's only being available in 9mm sized frames/magazines. There are 1911's available in 40 S&W that can take a significantly longer O.A.L.

    I can get rounds as long as 1.16 to feed through my XDm .40 magazines.

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    Member akgun&ammo's Avatar
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    The biggest problem is length of case, and the type of crimp. Some chambers cause the brass to stretch more than others. Some crimps cause a slight bulge at the case mouth.

    Either of these will cause problems.

    Rule #1 is if it feeds, it will normally fire.


    Chris

  4. #4

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    Quote Originally Posted by AKDoug View Post
    The biggest issue is feeding, then pressure. I honestly don't think that .01" is going to cause an issue, especially since it's on the long side, not the short side.

    The 1.135 length was set in the days of .40S&W's only being available in 9mm sized frames/magazines. There are 1911's available in 40 S&W that can take a significantly longer O.A.L.

    I can get rounds as long as 1.16 to feed through my XDm .40 magazines.
    I thought that was the case but with being new to reloading I'm somewhat paranoid which probably isn't a bad thing. I'm shooting an XDM so I would think I should get the same results.

  5. #5

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    Quote Originally Posted by akgun&ammo View Post
    The biggest problem is length of case, and the type of crimp. Some chambers cause the brass to stretch more than others. Some crimps cause a slight bulge at the case mouth.

    Either of these will cause problems.

    Rule #1 is if it feeds, it will normally fire.


    Chris
    What crimps cause a slight bulge and why? Interesting..

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    Member akgun&ammo's Avatar
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    dvarmit,

    Some of the earlier "factory" crimps. Lee was the first I saw, had two fingers that pressed into the case mouth and made two small ridges that sometimes bulged out. Another die set had a roll style crimp instead of a taper crimp.

    Chris

  7. #7

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    Quote Originally Posted by akgun&ammo View Post
    dvarmit,

    Some of the earlier "factory" crimps. Lee was the first I saw, had two fingers that pressed into the case mouth and made two small ridges that sometimes bulged out. Another die set had a roll style crimp instead of a taper crimp.

    Chris
    Thanks for the follow-up Chris.

  8. #8
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    Quote Originally Posted by dvarmit View Post
    Setup my rig for 40's last night and I had some trouble. In general I have 10-15 rounds that are 1.136-1.145 when the OAL should be 1.135

    Is this variation acceptable? If there is even a remote chance that it's not I'll get rid of them but I was just curious if there is any room for error in length with the 40..

    What are the rules for OAL with pistol rounds if there even is any?
    Reading thru this it seems some are referring to case length and you refer to cartridge length. Max COAL is 1.135" for the 40. You could get by with about .010" longer (1.145") if the magazine takes it and it likely will. The case length should be .840" to .850" for proper headspace and only a taper crimp should be used, no roll crimp, as the case headspaces on the mouth. You must crimp in a separate step or a crimp only die to avoid the crimp bulge. This will also give more uniform seating depth.

    If you have some that are slightly long, just run them thru again. Even if taper crimped they will seat deeper, then re-crimp.
    Is there nothing so sacred on this earth that you aren't willing to kill or die for?



  9. #9

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    Quote Originally Posted by Murphy View Post
    Reading thru this it seems some are referring to case length and you refer to cartridge length. Max COAL is 1.135" for the 40. You could get by with about .010" longer (1.145") if the magazine takes it and it likely will. The case length should be .840" to .850" for proper headspace and only a taper crimp should be used, no roll crimp, as the case headspaces on the mouth. You must crimp in a separate step or a crimp only die to avoid the crimp bulge. This will also give more uniform seating depth.

    If you have some that are slightly long, just run them thru again. Even if taper crimped they will seat deeper, then re-crimp.
    That's great to know.. I never thought about running them through again! Thanks!

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