Difference in bullet dimensions between lot numbers ??

[Creedmore]

I encountered something this evening that made me sit back and scratch my head.

While loading a batch of .309JDJ loads to take to the range tomorrow, I ran out of my first box of 150gr Nosler BT's, and opened another.  Upon seating the first two, the overall length was 0.010" longer.  A couple more, the same thing.  Surely my micrometer seater die couldn't have moved.

So, I pulled one bullet from the original lot, and compared with the new box.  Sure enough, ~0.010 longer in the new box, consistently.  Is this to be expected?  So, I adjusted the seating depth, and continued.

I am very picky about my loads -- make all my brass the same length, and measure every powder drop and OAL after seating.  With this particular load, I am within 0.005 of the lands - where this barrel has it's sweet spot for this load.  If I had not noticed the difference in OAL, I would have been into the lands and a possible dangerous pressure situation with near-max loads.

Anybody experience this?  I now have a new section in my log book especially for bullet length.  I will post any range results tomorrow.

Thx,
-Cm

[Graybeard]

It is not unheard of to have .005" to .010" difference in seated bullet length with bullets from the SAME BOX!

GB

[redial]

Like GB says, they vary from bullet to bullet, much less lot to lot!  I useta get all bent outta shape because my handloads for LR matches would vary so much until I started comparing bullet ogives. Well, no foolin! If there's 30 different contours in each box of bullets, you'll get 30 different seating depths.

Then I got all bent about segregating bullets per their shape until I noticed that the mixed ones shot exactly the same scores as the segregated ones.  Same story with weighing and segregating brass, to a greater or lesser degree.

Now I practice holding and squeezing instead and let the ammo take care of itself.

Redial
Too late smart, too soon old.