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acceptable variation oal


cnote
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What would you deem acceptable variation.  I know this is for relatively short range competitive shooting type distances

1.165  +/- .002 , .005???

just wondering when anyone actually measures after "X" amount of rounds reloaded

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I have done OAL for my 40 S&W and 9 mm. This was done out of curiosity. If I remember correctly I had a variation somewhere in the neighborhood of +/- .007” for my own cast bullets. I also separated into a couple groups, shortest OAL and longest OAL to see if there was an effect on accuracy. I saw no discernible difference in accuracy.


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Plus or minus .006. Most probably your seat die seats off the bullet ogive, because the bullet lengths by themselves will vary by as much as 6 thou. By seating off the ogive the length of bullet in the case is pretty much spot on.  Just measure a few bullets you’ll see they vary quite a bit. Add to this mixed range brass, and a host of other variables and this will drive you nuts try to get your oal’s the same. Set it and forget it.

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If I set the press up for 1.135 I’ll typically see 1.130 - 1.139 or 1.140.

 

I’m pretty convinced guys who get less than 8 to 10 thousandths of variation:

 

1) Are lying about it. Like guys exaggerate trigger weights, group sizes, and how many rounds they shoot a year. ;) 

2) Are sorting brass by headstamp. No thanks.

3) Have done aftermarket $ things to the press/shellplate/toolhead to make it more precise.

 

I consistently load ammo with .008-.010” variation which has single digit SDs and will shoot group sizes under two inches at 25yds. That’s more than sufficient to render myself the limiting factor. 😉
 

Edited by MemphisMechanic
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My OALs vary with different bullets and brass.  With PD JHP bullets OALS vary by +/- .005".  That is too much for me, because I have to load long and 1.165" is the max I can load a typical JHP to.  It's the -.005" that bothers me.  Everglades rounded ogive JHPs reduce the variation.  Montana Gold bullets and Hornady HAPs reduce it even more.  I'm currently using fully processed RP headstamp brass with 115 HAPs.  OAL variation is down to +.002"/-.000".  I now use all the mixed HS brass for minor loads.

 

FWIW, I use the flat seater stem so I'm pushing on the top of the bullet, not the ogive.

Edited by zzt
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11 hours ago, rooster said:

Plus or minus .006. Most probably your seat die seats off the bullet ogive, because the bullet lengths by themselves will vary by as much as 6 thou. By seating off the ogive the length of bullet in the case is pretty much spot on.  Just measure a few bullets you’ll see they vary quite a bit. Add to this mixed range brass, and a host of other variables and this will drive you nuts try to get your oal’s the same. Set it and forget it.

 

 Best answer above!

 

This man must be almost as smart, good looking and modest as I am. 😉

Edited by bigedp51
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If you do all that ZZT is doing you will get to +or- .001. But that’s a lot of work for this game. Take a sharpie and color the ogive of a few bullets. Take your seat die apart and place bullet in stem and rotate to remove sharpie. You’ll see that it’s removed at the same spot unless the bullet ogives are really off. So even though your oal’s are different the amount of bullet in side the case is the same. If you try and make all oal’s the same the bullet length inside case is now different. Find you max oal shorten by .015 and forget it. This way even if your rounds are off by .010 your .005 off the lands. Of course this is dependent on mag length and reliability. I use PD’s jhp and  they vary in length by at least .006 either way. In my Faxon G34 barrel I get a maximum oal of 1.095, with PD jhp’s, my target oal is 1.080. That’s it keep it simple.

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I’m wondering if the OP posted this to just get some conversation going. The topic has been covered before in various other posts.  But, I’ll add this; the more the bullets vary the more there’s a difference in OAL. 
 

PD FMJ RN are far closer in tolerances than coated bullets and I find them ever so slightly more accurate. However, the difference in accuracy is irrelevant in the sport. Now if I was shooting for precision/ bulls eye, then sorting brass, weighing bullets, OAL and exact powder measures would be more important. 
 

Loading for volume shooting without failures and adequate accuracy is what this is all about.  
 

 

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I load at 1.230

I accept anything in the thousands place, so anything from 1.220 to 1.240

I also know my gun will.chamber all of that. But I also try to get it as close to 1.230 as possible for competitions. If its beyond .005 i just use it for practice ammo

 

Also if you get the redding competition seating die all your loads will be all be as very close to what you set

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I bottom out my press twice on the down stroke.  I started doing that because I had primers that would stick to the decapping pin.  I founded that it didn’t shake off the primer any better than one bottoming out but my ammo length was much more consistent.  
 

In a same head stamp run I can get +\- .002.  

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4 hours ago, Aric said:

I bottom out my press twice on the down stroke.  I started doing that because I had primers that would stick to the decapping pin.  I founded that it didn’t shake off the primer any better than one bottoming out but my ammo length was much more consistent.  
 

In a same head stamp run I can get +\- .002.  

 

Lee resizing/decap die solved primer drawback for me if you're talking about a Dillon die.  It was the only thing I didn't like about my 1050.

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