OAL Tolerance

[racerngr1]

As many have probably figured out I'm new to reloading and still have alot to learn but am taking it very seriously. I have the most current Lyman reloading manual; however, one thing it doesn't say is what the tolerances are allowed to be when it comes to the overall length. What I have been doing in the past is keeping the tolerances within 1 thousandth (sp?) of an inch and running them through my G23 and it's been working fine. The manual says the OAL should be 1.125, so if it's 1.121, I will let it pass or if it's as much as 1.129 I let it go as well even though I try to get them as close to target (1.125) as possible. Is this ok or am I playing with fire and going to get burned one of these times.

Thanks for helping a newbie.

 

[rcmodel]

You should be fine.

Now that you have a dial caliper for reloading, you should measure a box of factory ammo sometime.

It will be a real eye opener I betcha!

rc

 

[racerngr1]

That's a good idea I will do that today.

 

[ny32182]

you have relatively tons of room for error in seating pistol bullets.

Even in match rifle bullets, you will see a few thousandths variation from min to max OAL. This has to do with inconsistencies in the tips of the bullets. Bullets themselves are not perfectly consistent.

 

[TooTaxed]

Actually, the OAL will change slightly depending upon the particular bullet nose shape you are loading.

Best practice is to fire a small test batch in your gun to verify functioning before handloading a large amount.

As an example, the 130-gr round nose lead ammo and commercial 185-gr HP that functions perfectly in my brother's 1911 wont function in his Kimber Ultra Carry. But seat the bullets slightly deeper...shorter OAL...and they function perfectly in both guns.

 

[Walkalong]

A .005 spread in O.A.L. (Say 1.260 to 1.265) is not unusual for pistol ammo. Often times we can do better, but .005 spread is nothing to worry about.

 

[rfwobbly]

OAL tolerances will vary with the press, bullet and brand of die.

• Different presses have different amounts of slack in them. Some depend upon the operator taking the lever all the way to the stop. Some progressives will vary wildly on the first and last rounds due to the press not having a full compliment of rounds.

• As was said, the shape of the ogive changes from bullet to bullet and can cause variations. Depending on the seating die ram, you make be more accurate with FP rather than RN, or vice-versa. Sometimes the lead nose will deform to different amounts simply due to the lack of steady operator force.

• Better brands of dies offer multiple seating rams for different shape bullets. If you are using one that pushes on the ogive (the shoulder of the nose rather than the tip), the OAL will vary with the shape or condition of the ogive. This since you are pushing on the shoulder, but measuring to the tip. FP can usually be seated to a lowest tolerance OAL, IF your dies are supplied with a flat anvil.

Here's a graphic showing how using the wrong anvil can cause OAL tolerances to soar.




There's no end to the way tolerances can creep in. That's why I advise adding total variation in OAL to your rifling setback. For example, if you are loading your ammo to be .005" off the rifling, but your OALs vary by .012", then obviously some of the bullets will be smashed into the rifling by .007" !!