What is going on here?

[whatsupdoc]

Replaced a tired criterion remage 223 barrel with a new same specs barrel. I used Berger 75VLD or 80VLD on the old barrel with excellent accuracy.

On the old barrel both bullets would touch the lands with only a few thousands difference, when I tried to measure the bullets touching the lands on the new barrel with 200 rounds through it the numbers seemed strange. The 75VLD measured 1.897 and the 80VLD measured 1.861. I use the Brownells tool for the measurements.

I checked and rechecked the measurements a dozen times different bullets with the same results so I took the bolt apart and rechecked using the Wheeler method (I think that is what it is called) and sure enough almost the exact same measurements.

So after going crazy trying to make sense of this all I went into my bullet stash and opened a new box of 80VLD's and sure enough when I measured these the number was right where it should be.

Has to be a odd lot of bullets or am I missing something.

Old Barrel
Berger 75 VLD	1.925
Berger 80 VLD	1.922
New Barrel
Berger 75 VLD	1.897
Berger 80 VLD	1.892
Old Lot Berger 80 VLD	1.861

 

[ricco1949]

"Has to be a odd lot of bullets..."

That'd be my guess too..

 

[coldboreshot]

Unless I'm missing something here,
Have you taken into consideration the throat errosion? I guess it depends on what "tired" barrel means.

 

[whatsupdoc]

Not throat erosion, even when old barrel was new jam difference between the two bullets was small. The new barrel has really no erosion.

 

[coldboreshot]

Was the same chamber reamer used on the 2nd barrel as the 1st one?

 

[coldboreshot]

How many total rounds on the previous barrel?

 

[coldboreshot]

I ginf it quite extreme, the difference between two lot#'s of these bullet dimensions are .030". I've been through a ton of Berger bullets in my time in different calibers and different bullet shapes but have never encountered a .0.030 difference in dimensions but I guess its not impossible.

 

[STS]

Different point up die used on the Old bullets. Different ogive.

 

[L.Sherm]

I've seen .020 difference in lots of Bergers

 

[whatsupdoc]

Was the same chamber reamer used on the 2nd barrel as the 1st one?

The same "dimensions" chamber reamer but not the same physical reamer,
Old barrel had a little over 4600 rounds through it.

 

[coldboreshot]

At 4600 rounds, I could see errosion of the lead at about .030". Would explain why your base to ogive measurements are off by .030" in length from previous barrel to new. (With both grain vld's).
According to your description, your establishing seating depth by just touching the lands. If the errosion of the lead is .030", you are now backing up (reducing) your seating depth based on the fresh lead (new lands) of the new barrel. Each differential is .030" between each bullet, 75 vld and 80vld, according to your chart.
Highly unlikely each one of the bullet lots are both "off" in dimensions, and especially .030.
My wager is riding on a .030" errosion of the old barrel. At 4600 rnds???? No doubt.

 

[Coyotefurharvester]

Too many apples and oranges in the same basket.