kilotanker22
New member
Recently I switched bullets in my 6.5 Creedmoor from the 140 grain Nosler Custom Competition bullet, to the 145 grain Barnes Match Burner. The obvious reason for me was the high G7 BC value. I bought a box of 100 bullets at first and they shot pretty well and were reasonably consistent, so I bought 1000 more.
Fast forward a few hundred bullets and all of a sudden my .25-.3 moa rifle became a 1 moa rifle. I have never shot it very warm and I am only a few hundred rounds down the tube anyway so I am not worried about the barrel.
Velocity had not changed any discernable amount and velocity spread is still the same so I ruled out my powder and primer. My case prep is also not the issue, (I painstakingly make sure that every single case is identically prepped and sized. Any cases with any variation from nominal after sizing is set aside and used for warm up/practice.
Next I looked to my bullet seating. I had just ten rounds still loaded so I decided to measure the cartridge base to ogive and the cartridge base to shoulder datum, looking for something out of whack. I found the cartridge base to datum measurement on all ten cases to have less than .0005 variance across the lot of ten. I then measured cartridge base to ogive and found a runout of .008"... Not OAL, this was CBTO. I pulled those ten bullets and measured bullet base to ogive and found about the same variance between them.
Due to the ogive location variance of the bullets, my distance to the lands is varying by as much as .008". This brings me to the conclusion that the changes in barrel time and harmonics is what increased my average group size. I do understand that 1moa is still an ok shooter, but this is a quarter minute rifle and load, not 1moa.
To verify that this was not a mistake I made by potentially mixing lots, I checked all of my boxes and this box of 500 is the only one open, so all of the bullets came from that box. Then I took a sample of 50 and measured an overall variance of about .008" across the sample of 50. I did not bother to calculate the standard deviation, but observed about 20% of the bullets at the lower end and about 20% at the higher end of the measurements. The rest were pretty consistent with only .001-.002" variance across approximately 60% of the sample.
I opened a second 500 count box and measured a sample of 50. I found no more than .002" variance across the entire sample for the bullet base to ogive measurement. I also decided to compare these to the 250 count box of Nosler Custom Competition bullets that I have left. I took a sample of 50 bullets from the Nosler box and found less than .001" extreme spread across the entire sample. Now I need to decide to keep using the Barnes, of which I have around 1000 bullets, or to switch back to the Noslers, or find another bullet.
I am thinking maybe I just got a less than perfect box of bullets. I do wonder if Barnes might replace them. I am not upset really, just figured I would share an experience that had me baffled for a few days.
Before anyone says it, I have checked the rifle and optic thoroughly. I am nearly certain that the bullet is my problem. I guess the next step is to test the other lot of bullets to see if the problem persists.
Fast forward a few hundred bullets and all of a sudden my .25-.3 moa rifle became a 1 moa rifle. I have never shot it very warm and I am only a few hundred rounds down the tube anyway so I am not worried about the barrel.
Velocity had not changed any discernable amount and velocity spread is still the same so I ruled out my powder and primer. My case prep is also not the issue, (I painstakingly make sure that every single case is identically prepped and sized. Any cases with any variation from nominal after sizing is set aside and used for warm up/practice.
Next I looked to my bullet seating. I had just ten rounds still loaded so I decided to measure the cartridge base to ogive and the cartridge base to shoulder datum, looking for something out of whack. I found the cartridge base to datum measurement on all ten cases to have less than .0005 variance across the lot of ten. I then measured cartridge base to ogive and found a runout of .008"... Not OAL, this was CBTO. I pulled those ten bullets and measured bullet base to ogive and found about the same variance between them.
Due to the ogive location variance of the bullets, my distance to the lands is varying by as much as .008". This brings me to the conclusion that the changes in barrel time and harmonics is what increased my average group size. I do understand that 1moa is still an ok shooter, but this is a quarter minute rifle and load, not 1moa.
To verify that this was not a mistake I made by potentially mixing lots, I checked all of my boxes and this box of 500 is the only one open, so all of the bullets came from that box. Then I took a sample of 50 and measured an overall variance of about .008" across the sample of 50. I did not bother to calculate the standard deviation, but observed about 20% of the bullets at the lower end and about 20% at the higher end of the measurements. The rest were pretty consistent with only .001-.002" variance across approximately 60% of the sample.
I opened a second 500 count box and measured a sample of 50. I found no more than .002" variance across the entire sample for the bullet base to ogive measurement. I also decided to compare these to the 250 count box of Nosler Custom Competition bullets that I have left. I took a sample of 50 bullets from the Nosler box and found less than .001" extreme spread across the entire sample. Now I need to decide to keep using the Barnes, of which I have around 1000 bullets, or to switch back to the Noslers, or find another bullet.
I am thinking maybe I just got a less than perfect box of bullets. I do wonder if Barnes might replace them. I am not upset really, just figured I would share an experience that had me baffled for a few days.
Before anyone says it, I have checked the rifle and optic thoroughly. I am nearly certain that the bullet is my problem. I guess the next step is to test the other lot of bullets to see if the problem persists.