Help - one keyhole

[Nomad47]

I went out today to shoot my new 6XC. It is a Savage 12 BVSS with a 28" 8 twist Criterion barrel. 17 rounds have gone down the tube before today. Today I was shooting 3 three shot groups at 100 yards after shooting two to sight back in after making a Burris ring insert adjustment. On the third shot of the third group, the bullet keyholed. Velocity was 3197 on the keyholed round and the previous two were 3188 and 3205. 105 Amax bullets.
The only thing I can think of is it was just a bad bullet.
Any ideas or comments?
Edit: The Keyholed bullet was 4" left and 3" down from the other two.

 

[K22]

I agree, this sounds like a defect bullet. I'm not a big fan of weighing bullets but in this case you may want to check the remaining bullets you have from that lot.

Here are some other thoughts:

- Did the spent primer look normal?
- Was the report and recoil from the rifle normal?
- Any possiblity of significantly under charging the round?

 

[Nomad47]

Thanks, K22.
The spent primer looked normal - just like the previous ten. I didn't notice any difference in the report & recoil. The velocity was actually in between the other two like charges.
It was weird. Looking thru the scope at the group, I only saw two holes. Then I noticed this oblong hole several inches low and left of the first two holes, which were nice and round and 1/4" apart. I even pulled the bolt and looked thru the barrel. The first I did when I got back to the motorhome was clean the barrel. And I paid close attention to the first patch.
The only other time I have seen a keyhole on paper was when a gunsmith mistakenly installed a 14 twist instead of a 8 twist. That was ugly.

 

[Nomad47]

I called Hornady this morning. They wanted me to send the rest of that box of bullets.

On closer examination, the second three shot group had bullet holes that were closer to 7mm than 6mm. It would appear the bullets were wobbling as they passed thru the paper.

 

[Flybuster]

I hope you don't have a repeat of this: http://riflemansjournal.blogspot.com/2011/10/equipment-rare-krieger-mistake.html

 

[KMart]

If you haven't already, check your twist rate. I am pretty sure that the twist rate is already on your mind.
Are the bullets nekked or coated?

 

[GermanS1]

Yes, check the twist rate (it certainly drove me crazy when it happened to me) and if it checks out, try a box of Sierra 107 MatchKings through it. Hopefully it was a bullet problem - much cheaper to fix!

 

[Nomad47]

Bullets are hBN coated. I also coated the barrel just before firing the first shot thru it a few days ago. BTW, the first 17 shots all had round holes in the paper and were seated .003 into the lands.
When I saw the keyholed bullet hole, the first thing that entered my mind was twist rate. But the slowest velocity had nice little 6mm round holes. The average velocities for my three groups were 3098, 3140, and 3197 fps. I had a leftover from sighting in so the first and slowest group had 4 shots - all holes were nice little 6mm round holes with a black edge which I assume was caused by the coating. The 3140 fps group had 7mm holes with no black edge. The third and fastest group had the first two shots make the same 6mm holes with the black edge. Then my third and final shot of the day keyholed.
Of the 28 shots fired down this barrel, except for a couple sighters, all shots have been within 1/2" of POA except the keyholed shot.
I've got three test loads made with 105 AMax bullets ready to take to the range. The bullet box these came from is not labeled AMP jacket. I'll make an update post this evening.
Thanks for all the help and suggestions so far.

 

[spclark]

How are you applying hBN to your bullets?

My first thought upon reading your initial post was to ask if by chance you could tell from the keyhole if the plastic tip may have come off. I've seen this happen before, believe it's happened to me to a few years back, despite posts suggesting pulling the tips off (!) before use doesn't affect accuracy. I maintain that's no true test as results will be different if tips come off in flight.

Perhaps the lot was defective, perhaps coating operation caused some tips to loosen. Hornady ought to know once they see 'em but I doubt they'll pass along their findings.

 

[Nomad47]

Thanks, Stephen. Yes, I'm afraid I won't get a lot of information back from Hornady.

I coat the bullets in a vitamin bottle in a tumbler. The bottle has coated BBs in it. I have a single shot follower in the top of the magazine and I gently push the loaded rounds into the chamber, so I'm fairly certain the plastic tip was still on the bullet when it left the barrel. But who knows what happened in flight.
The middle group, 3140 avg MV, had large but fairly round holes. The holes didn't have that black edge around them that I usually see and were about 7mm diameter. Its almost like the Hornady's didn't like a particular velocity range. I'll post a picture soon - maybe that will help.

 

[Nomad47]

Here's a pic. The holes on the left group aren't as small and crisp as the two holes on the right group.