Bullet Lots - COAL and CBTO Inconsistencies

[BlueWater]

Doing a couple of ladders for a 6.5G AR and had to move to a new bullet lot from ladder 1 to ladder 2. Bullets are 123gr. Hornady ELD-M, using Redding dies.

Found something I find very peculiar:

Everything is identical other than powder type and weight: processed at the same time, through the same dies without adjustment, and press etc. Was targeting a COAL of 2.260 as a first go.

Lot A (loaded 50 rounds):
Adjusted die to: 2.260 OAL = 1.688 CBTO
These 50 rounds measure quite consistently

Lot B (loaded a handful before I noticed this):
Did not change seating depth on die: 2.270 OAL = 1.678 CBTO

From Lot A to Lot B the same process resulted in a COAL increase of 0.010" BUT the CBTO has decreased 0.010". I'd be surprised enough by the OAL moving .010" but to see the CBTO move .010" in the opposite direction has me confused. I was expecting to see the CBTO increase the same .010"....

Does this make sense or am I making a big deal out of nothing?

 

[BlueWater]

It occurred to me this morning that the problem is obviously in the bullets and that I should look at them by themselves (without being loaded).

Lot A Bullet ONLY Measurements:
Bullet Base to Ogive: 0.657"
Overall length (bullet base to tip): 1.231"

Lot A Bullet ONLY Measurements:
Bullet Base to Ogive: 0.652"
Overall length (bullet base to tip): 1.246"

I placed several rounds from each box on the scale just to confirm they are in fact 123gr projectiles and there wasn't a mixup at the factory.

New to precision rifle reloading. Are big variations like this normal from lot to lot (0.015" base to ogive variance)?

 

[harleytuner]

Yes, you need to measure and adjust your dies everytime you change lots. Same thing with powder, if you change powder lots you might need to change the charge