Seating depth discovery....and question

[Bullmark]

So I made an interesting discovery last night. I don't re-load, so I generally order from one particular company online. I think highly of them and have been pleased over the years. Roughly 2yrs ago I had a rifle built, a .280AI, and used by online source to find a load that shot well for hunting purposes. I settled on a Berger 168vld and 57gr of H4350. We also tinkered with the seating depth and after moving a smidge closer to the lands, the rifle was shooting better than I could've asked for.....so we stopped and called it good. I then ordered a couple hundred rounds and figured they would last this rifle a long time.
So last night I was organizing my ammo storage and for some reason decided to look at those .280AI rounds. I've put around 25 rounds through since settling on a recipe and stocking up....but I had shot rounds from 3 different boxes. So I had 3 boxes that were all roughly half full (10-12 per box).
When I sat two loose rounds beside one another it was obvious that one was a good bit longer. I then frantically went through every box and compared each round. Somehow the seating depth on some of the rounds was different.
All total I found 17 rounds that were "shorter".....out of 165.....I'll say approx b/c my dog bumped into the table and set off a domino affect and rounds fell everywhere.
The pics show the actual difference. My question is 1) is this considered a big difference, from a seating depth perspective? I'm a real newbie to reloading and the long range game.....so pardon my ignorance.
2) I wonder what difference it may have made when I was confirming distances and setting up my turret? I have no way of knowing how many short ones I shot or when I shot them.
3) I guess I'll pull the short ones and confirm my specs.....but is there anything I'm missing?
Thanks to everyone in advance for the advice and candor. I love this site.

 

[Huntsman66]

So was your load worked up on the shorter or longer case?

 

[74honker]

IF, they seated measuring off the ogive and not the tip there can be a little fluctuation in COAL.

 

[Huntsman66]

Also if you can don't measure OACL to the tip of the bullet, you really want to measure the ogive with a comparator. Bullets can be slightly different when comparing their overall length

 

[vancewalker007]

You have somewhere around 60/1000 inch difference there. That can make a fairly massive difference in how a round will perform on Point of Impact (POI). But, you really need to measure the Cartridge Base to Ogive (CBTO) distance not Over All Length (OAL) for determining equality between rounds. The meplat on the bullet can vary a lot bullet to bullet contributing to a difference in OAL. But you do have enough difference there that the rounds will likely shoot to different POIs. I typically think of OAL as a coarse measurement to make sure a round will fit into a magazine and not really useful for performance tuning. Dropping rounds on the floor can contribute to bullet offset if you have low neck tension. Lock the dog out when you're working on ammo so you don't have a 52 pickup game .

 

[Bullmark]

Thanks guys, I measured the overall length because I figured the same bullets, both Berger 168 VLD Hunters, should have the same measurements for any comparison.....as long as the tips aren't damaged. I do understand that overall length can vary from one type of bullet to the next.
I'm wondering how it happened ? My best guess is my specific reloads had a box of "standard" .280ai (same bullet same Nosler brass) shipped inadvertently. You can order from the site and only specify the bullet and brass.....I have no idea the powder, charge volume or seating depth that would be used for such an order.....but I'm betting that's what I got. If that's the case, it means I only shot 3 of the shorties, which would make me feel better, and explain the occasional flyer that I was blaming on my poor shooting...lol.
I will be looking a lot closer at every box of ammo that I buy from now on, factory or hand loaded.

 

[Subzero]

That's a huge difference in coal, considering that it's the same bullet. How much of an effect on accuracy really depends on the rifle.
Only way to know is shoot some groups.

 

[soewe812]

Looks like 2 different bullets. They could both be seated the same distance from the lands. Bottom pic looks like a berger vld upper pic more like a sierra match king.

 

[Bob Wright]

Call the cartridge manufacturer and explain it to them. They may/should have the length those were loaded to. Resetting the depth is tough if you don't reload. That's where you need to reach out to someone who does and has dies, bullet puller, measuring tools. Many here have just such equipment.

 

[L.Sherm]

Looks like 2 different bullets. They could both be seated the same distance from the lands. Bottom pic looks like a berger vld upper pic more like a sierra match king.

I think you hit on something, sure looks like it from the picture.

 

[Bullmark]

It's def the same bullet. The lighting may make it appear slightly different but I'm sure it's the same. Isn't there an industry spec that factory loads must follow? I thought maybe that's a spec load, and what you would get when you order without specific seating depth requests. I can easily see how a box of "off the shelf" spec rounds would inadvertently get sent to an order with a more detailed recipe. In this case they happen to shoot pretty similar to the ones closer to the lands, because every group I shot, out to 300yds, was under .5moa.
Regardless, I think I'll set those aside and shoot a few groups with the chosen rounds....if it's still shooting good groups I'll call it good.

 

[misterc01]

Agree - a COAL measurment is only useful for magazine lengths - you need to go off the ogvie to get a CBTO measurment. If they are the same, all is good.

 

[Dosh]

Perhaps recheck the boxes, maybe one is 168 Classic Hunter. Agree measure by the ogive. I've seen differences in length of a bullet but not this much.

 

[L.Sherm]

It's def the same bullet

Can you take a pic of the 2 side by side?