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- COMPENSATE FOR MIXED RANGE BRASS CASE LENGTH VARIATION
- HOW TO OBTAIN MORE CONSISTENT OAL/COL
Repost from another thread - http://www.thehighroad.org/showthread.php?p=9916478#post9916478
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.
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 these reasons, 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.
- HOW TO OBTAIN MORE CONSISTENT OAL/COL
Repost from another thread - http://www.thehighroad.org/showthread.php?p=9916478#post9916478
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.egd said: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.
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.
+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.243winxb said:A variance of .005" maximum is normal for a single stage press. Up to .010" for a progressive.
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)egd said:I am using a Lee classic cast turret press ... Do those of you using a single stage press get variances also?
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.Or do those variances in OAL really matter?
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 these reasons, 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.
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