Box to box difference in ogive

[Broc]

I have a question for the more experienced reloaders. What is the expected variation in bullet ogive when using bullets from different boxes?

For example, I'm loading .223 with 69 SMK loading 0.010" off the lands. I loaded 10 rounds measuring 1.800" +- 0.001". I used up one box, opened another from the same lot number and continue reloading. Now my ogive measurement has moved to 1.807 +-0.001" for the next 10 rounds. Is this sort of change normal?

I thought the whole purpose of measuring off the ogive was to get a consistent measurement from bullet to bullet. Does this not apply when changing from box to box?

 

[jrob300]

Re: Box to box difference in ogive

Are the two boxes from the same lot? I've seen fairly large differences lot-to-lot (.020-.030"). Some guys sort their bullets by bearing area due to what you're seeing (using two gauges, one on the boattail and one on the ogive) For LR shooting this will affect your velocity (ES).

John

 

[Broc]

Re: Box to box difference in ogive

jrob300, Yup, same lot. It's not that big of a deal if it is something normally seen from one box to the next. I'll just have to remember to check and re-adjust whenever switching boxes to maintain my ogive length.

 

[bohem]

Re: Box to box difference in ogive

The example Jrob mentioned compares well to my experience with them, lot to lot is very large variances. In the same box I've seen "float" of as much as 10 thousandths.

It's entirely possible that your Lot A box 1 came from the start of the lot and Lot A box 2 came somewhere towards the end.

Also, I've heard it explained a couple of times that the Sierra's are run by multiple machines and dumped into the same giant bin.

 

[Broc]

Re: Box to box difference in ogive

Ok. That makes perfect sense. So if I understand correctly, I will just have to load box A and then re-adjust my seating die to seat box B to the same ogive measured length?

I appreciate the responses. I'm fairly new to precision reloading. Always been a COAL length kinda guy.

 

[vman]

Re: Box to box difference in ogive

COAL should be thrown out the window unless your loading mag length. Otherwise, ogive readings are a hell of a lot more consistant.

 

[bohem]

Re: Box to box difference in ogive

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Broc</div><div class="ubbcode-body">Ok. That makes perfect sense. So if I understand correctly, I will just have to load box A and then re-adjust my seating die to seat box B to the same ogive measured length?

I appreciate the responses. I'm fairly new to precision reloading. Always been a COAL length kinda guy.

</div></div>

Yes, although some people have reported +/-10thou in a single box (20 thou total variance) which has prompted them to sort by bearing surface length before seating.

This tendency, along with the slightly higher price than Hornady's bullets has driven me away from Sierra's generally. I haven't had anywhere near that much variance in Hornady offerings. If I need something more aggressive than an Amax for a specific purpose I've turned to Berger.