OAL variance

[egd]

I notice that reloaders list exact OALs like 1.089 or 1.135 etc. etc. But my lengths will vary a little. Current setting varies from 1.129 to 1.134 with most around 1.131 to 1.133. I am using a Lee classic cast turret press and I notice that when I press the bullet up into the seating die that the turret flexes a little. I'm thinking that this is where my variance is coming from.
Do those of you using a single stage press get variances also? I realize there are small differences in mixed case length and bullet lengths, but it would seem to me that if you have a ram/shell holder squeezing in on one end and the die on the other, that whatever those differences are would be absorbed inside the shell.
Or do those variances in OAL really matter? I can't tell it on my targets. But I'm not that good anyway. And I'm not loading anywhere near max or anything-just target loads.

 

[243winxb]

A variance of .005" maximum is normal for a single stage press. Up to .010" for a progressive. Measure on the ogive for better accuracy.

 

[LiveLife]

+1. Depending on the brand/manufacturing process and type of bullets/nose profile along with how rough the shipping company employees treat the bullet boxes (that could cause the bullets to be out of round), you will have variations in OAL/COL, especially for progressive press with shell plate tilt/deflection.

I am using a Lee classic cast turret press ... Do those of you using a single stage press get variances also?

Yes, due to reasons posted above. AFAIK, Lee pistol dies have rounded bullet seating stem that pushes on the side of the bullet tip (ogive) and not the tip. So different bullet nose tip geometry will produce different OAL. And don't worry about the "floating" turret as the final OAL/deepest bullet seating depth will be produced when the turret is pushed up against the frame (same for Pro 1000/Load Master). (Using resized brass in progressive press will reduce shell plate tilt/deflection and using the proper/custom bullet seating stem will produce more consistent OAL/COL)

Or do those variances in OAL really matter?

Not that significant if you are not at max OAL as gas leak during "bullet jump" from case neck to start of rifling will absorb some chamber pressure variance.

However IMHO, if you are using max OAL and did not factor in resized case length variations from mixed range brass, this may affect chamber pressure variance enough to show on chrono/target group size.

If the resized case length variance is too great, shorter cases won't headspace on the case mouth but rather off the extractor (essentially rattle loose inside the chamber until the expanding gas pushes the case base against the breech wall face). Due to this reason, when I am conducting load development with mixed range brass for max/working OAL determination, I will measure the variance of resized case length and subtract the average variance and use it as my "Revised max/working OAL/COL" to compensate.

 

[LiveLife]

I notice that reloaders list exact OALs like 1.089 or 1.135 etc. etc. But my lengths will vary a little. Current setting varies from 1.129 to 1.134 with most around 1.131 to 1.133.

That's the target we aim for. Depending on the press type/bullet brand/brass condition etc., reloaders may experience +/- several thousdandths to even hundredths in OAL/COL variation.

It's similar to powder charge used. We may aim for say 5.0 grains but depending on the measure/powder used, we may get +/- .1 gr variance to .2+ gr variance.

 

[egd]

OK, thanks a bunch. Al that is good to know. It's funny, to me anyway, all this reloading science/art is so precise...except when it's not.

 

[LiveLife]

Yes, that's why this category is called "Handloading and Reloading".

Handloading for using new/once fired/prepped brass and more precise reloading practices with single stage press to get utmost accuracy.

Reloading for using once/multi fired brass with SS/turret/progressive press to get decent accuracy and higher volume at lower cost point.

There are many reloading variables.

Working with various aspects of reloading whether component selection and/or reloading practice is what makes this hobby interesting. For some of us, the goal is simply to make cheap ammo to shoot. For some it's to make more accurate ammo than factory. I am a reloader who wants cheaper ammo that shoot accurate as possible using mixed range brass (my cheapest reloads shoot more accurate than most factory ammo).

Like engine building and auto racing, speed costs money. How fast/quick you want to go often depends on the size of your wallet. My reloading wallet size is not that big to afford new or even once-fired brass.

Many in manufacturing will say, "There are speed, quality and low cost. You can have two out of three but not all three". Kinda similar for reloading.

 

[gamestalker]

OAL's are inconsistent either because the tip is lead, thus deformity in shipping or other causes. Or because the location of the olgive varies.

I load on single stage presses, and oal still varies pretty significantly measuring from datum line off the olgive to case head. I just loaded some Nosler Silver tip Ballistic tips the other day, and I was seeing variations of up to .010", and it wasn't press flex causing it.

IMO, what really matters, is the consistency from the olgive to the lands.

GS

 

[Walkalong]

I log all of my OALs. I typically log something like 1.130 to 1.135, or 1.163 +/- .001, etc., etc Depends on the variance and where the OAL falls.