Newbie Qs on Bullet Lots

[Radosilver]

This week I loaded 51 rounds of .270 Win. Bullet is a Hornady Interlock 140 grain BTSP. The first 49 finished off one box of bullets I'd purchased about 2 years ago. The last two rounds were from a brand new box I purchased within the past year. The seating depth of the first 49 were all consistent with a length of 2.753" measured to the ogive, and an overall length of about 3.273". The last two measured to the ogive were 2.726", so 27 thousandths less, but the overall length stayed the same. So, unless I'm missing something, this tells me the seating dye didn't magically move for the last two rounds, the bullets are actually shaped differently. With this, I have two questions:
1. Is it common to have bullets from different lots shaped this much differently?
2. Am I correct in assuming my group sizes and velocities will likely change when I burn through the 40 or so rounds I have left and load up more rounds from the new box? I was planning on ordering a CDS dial from Leupold to see how well it works on this .270, but am thinking my velos and/or group sizes may change with the new box of bullets, so I may not want to do that.

 

[Lawnboi]

1. Yes fairly common to have different lots be different, especially from Hornady.

2. Only way to find out is test. Your barrel will change throughout its life, part of the reason a cds gives false confidence.

 

[TaperPin]

Bullets and powder can be enough different from lot to lot to be able to tell on the target, although 99percent of the time it’s not enough that most people notice.

 

[Radosilver]

1. Yes fairly common to have different lots be different, especially from Hornady.

2. Only way to find out is test. Your barrel will change throughout its life, part of the reason a cds gives false confidence.

Thanks. Is there a certain round count where you tend to see things change with the barrel?

 

[Lawnboi]

Thanks. Is there a certain round count where you tend to see things change with the barrel?

A barrel will normally speed up around 100-200 rounds Ime. Honestly I’m less worried about the barrel changing than I am the bullet/powder/reloading consistency change. Even my match gun, shooting same lot powder/primers/bullets/brass it’s not uncommon to see velocity change through the life of a barrel, even sped up. It’s not uncommon to see a change with seasonal weather changes as well.

You’re doing yourself a favor learning the mil and moa adjustments and going from there, allows you to be flexible to those changes.


But to easier answer your question, when swapping lots of bullets when I have to, I’ll go confirm velocity and zero again, it truly is the only way to tell if it’s the same, worse, or better.

 

[willfrye027]

This is why I like to find a bullet that works and order enough for the life of the barrel. It probably doesn’t matter in the end but it sure makes me feel better knowing they’re from the same lot. Same deal with powder and primers..8lb jugs and cases of 5000 primers are where it’s at

 

[Radosilver]

Thanks all.

 

[DaveCB]

1. Is it common to have bullets from different lots shaped this much differently?
Yes and within the same box. Use a compatitor and measure from the base of the bullet to the ojive .
If you measure a 100 bullets you will see a spread that resembles a bell curve.
I do not measure hunting bullets but I do measure all my match bullets and group them in like sizes.