OAL for accuracy

Discussion in 'The Ammo Can' started by MTgrizz, Jan 21, 2013.

  1. MTgrizz

    MTgrizz XDTalk Newbie

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    I am new to pistol reloading. I have reloaded a lot of ammo for bolt action rifles. The biggest gains in accuracy I saw in rifle ammo was loading the bullet out as close to the rifling in the barrel as possible without actually contacting it. I assume the same thing holds true for a pistol.

    I realize that bullet shape has a lot to do with it, but what oal do most of you use in your XD's to gain accuracy and still fit in the mag and function? I obviously wont be decreasing oal below the recommended load data due to the potential for increasing pressure.

    I have loaded a few rounds for my XDm 40 4.5" that are fairly accurate (probably more accurate than I can shoot them) but I can probably do better. Everything I have loaded so far has been at 1.125".

     
  2. Mercmar

    Mercmar XDTalk 5K Member

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    I load a lot of rifle and handgun ammo. I use the Hornady tool for determining o.a.l. for my precision rifle loading. I load pistol ammo so that it feeds well. I don't believe you'll notice a measurable difference in accuracy in handgun reloading, based on o.a.l.
     
  3. agalindo

    agalindo XDTalk 15K Member Founding Member

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    +1 on Mercmar's comment.
     
  4. 57K

    57K XDTalk 2K Member

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    Depending on the bullet style, 1.125" is probably a good OACL. If I were loading for only 1 9mm pistol I would find the max. allowable OACL where the bullet just touches the lands with a specific bullet and then shorten that OACL by .005" like you'd do in rifle reloading. Let me mention this also, all of my jacketed loads use JHP bullets. I don't use FMJ or plated. For economy, I just use cast lead.

    Since I have multiple 9mm pistols with both long and short throats, I tend to use 2 different OACLs for JHPs. I've been doing it this way for a number of years with very good results and the OACL recommendations come from Vihta Vouri's metric OACL recommendations. For pistols with long throats like SIG, Glock and Ruger, I use 1.142"/29mm. For pistols with short throats like XD/XDm, some S&Ws and CZs, I use 1.122"/28.5mm. This has worked very well but you still need to establish the max. allowable OACL for your specific pistol with the specific bullet you intend to use.

    And, welcome to the forum from Texas. ;)
     
  5. fredj338

    fredj338 XDTalk 10K Member

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    ^^THIS^^ In a high dollar match pistol w/ custom throated bbl, adjusting OAL might get you some measureable accuracy benefit, but not much. In production guns, probably nothing. Consider that most 38sp are more accurate than their shooters @ 50yds & the wc bullet is waaaaay far from the lands.
    Even in rifle loads, adjusting OAL is the last thing I do to tweak a load. The bullet & powder combo are more important.
     
  6. szhttm

    szhttm XDTalk 500 Member

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    For the XDm 40S&W, the most common OAL used by competitors is 1.145. The maximum length you could try is 1.150. After that, I believe you will encounter issues with reliable feeding of the ammo because the ammo will be rubbing on the inside of the magazine.



    Good Luck And Be Safe!!!
    :cool:
     
  7. 57K

    57K XDTalk 2K Member

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    MTgrizz, sorry, I was talking about 9mm where there is much more variance in chamber lengths. Various brands of .40 S&W chambered pistols are much closer in chamber length due to the smaller variation in .40 S&W loads. For JHPs, I used the 1.125" OACL the most for JHPs, but have loaded from 1.120 - 1.130" due to different bullet styles and OACL recommendations. For cast loads I would use the OACL specific to the chamber and bullet style as I mentioned earlier and load bullets .005 - .010" off the lands. Not necessarily for accuracy but for safety and functioning issues. When cast bullets are loaded too long you can get out of battery issues. Too short and they may not function as well. ;)
     
  8. MTgrizz

    MTgrizz XDTalk Newbie

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    After some trial and error, I cannot get my 155 gr SWC lead bullets to contact the rifling at all. The rounds get long enough that they will not fit in the magazine.

    I loaded a couple long dummy rounds and dropped them in the chamber to see if I could get contact. The long rounds would not eject when I tried to clear the chamber. I suppose I can play around with a couple .001 and see what happens, but it doesn't look like there is much room to play with oal in my XDM.
     
  9. agalindo

    agalindo XDTalk 15K Member Founding Member

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    You don't to that with and XD. There's no reason for it. FYI you don't want a load that contacts the rifling it will cause excessive pressure. In RIFE rounds you want the to be a few thousands before contacting the rifling not contacting it.
     
  10. MTgrizz

    MTgrizz XDTalk Newbie

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    edit to remove double post
     
  11. 57K

    57K XDTalk 2K Member

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    You have to remember that OACL can't exceed the max. OACL recommendation because your rounds won't fit the magazine and may be too long for the chamber unless you're using a custom pistol like a 1911. Your cast lead loads have to be shorter than the max. allowable for the chamber, where the bullet first contacts the lands. Like I said earlier, shorten by .005 - .010". Then you have to make sure that the load fits the magazine. ;)

    For most SWCs, I used 1.135".
     
  12. fredj338

    fredj338 XDTalk 10K Member

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    Pistol bullets jambed into rifling offers you nothing but problems. At the worst, pressure spikes, at teh least, a round that sticks in the bbl & when you have to hand cylce it out, it either jambs or leaves the bullet in the bbl & spilled powder in the gun. Get it out of your head that you gain any accuracy advantage trying for this, you do NOT.
     
  13. JustSomeGuy

    JustSomeGuy XDTalk 2K Member

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    Loading long in any particular pistol caliber only gets you some reduced pressure effects. In my experiments I do not notice much if any accuracy difference from various OAL/bullet combinations. The common wisdom about loading as long as the chamber will allow is viable only insofar as it reduces slightly the pressure from maximum loadings.

    However, pressure can and does INCREASE if your pistol bullet is touching or is too close to the lands. Pistol powders are not like rifle powders. They are, as a class, much faster than rifle powders, and if the bullet is touching or very close to the rifling in the barrel, then the bullet cannot move sufficiently at the start of the combustion process to give the proper pressure cycle.

    Do not load pistol bullets into the lands. You will spike pressures beyond what the "book" tells you you should expect, and if you are loading near the maximum things could go wrong.
     
  14. 57K

    57K XDTalk 2K Member

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    JSG is correct, at a given powder charge, the longer the OACL, the lower the pressure will be. It might be slight in some cases, depending on the powder used, but if you're loading near or at a max. charge, it can help to keep your handload from exceeding the max. recommended pressure.

    The only time a bullet should touch the lands is with a "dummy" round where you put a bullet into an inert/fired case, put in the chamber and push by hand or very light taps with a plastic mallet until the case stops. Remove the bullet and measure for OACL. Repeat the process until you've done it about 5 times to make sure the OACL is consistent. That is the MAX allowable OACL. Then you reduce that OACL when you begin loading/seating by .005 - .010", or in the case of the .40 S&W, 1.125" for JHPs, 1.135" for LSWCs should work just fine. ;)
     
  15. fredj338

    fredj338 XDTalk 10K Member

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    An easier way to measure that max COAL is put an empty case in the chamber, close it, measure w/ a rod down the bbl & mark the rod. Then put just a bullet in & hold it in place against the lands. Now measure that w/ a rod again. Then just subtract the diff. Easier & more accurate IMO, works for rifles & pistol.

     

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