Interesting occurrence during load work-up this weekend...

[Moonshine44]

Let me preface this by saying that I have a .264LBC barrel from Black Hole Weaponry with their matching bolt in my AR. I worked up some loads using new Hornday brass, 120 grain A-Max bullets (that weight is what I could find when I started shopping for bullets, so I have a bunch of them) and 8208XBR powder this weekend, starting with 27 grains and working up in half-grain increments to 28.5, five rounds per load. I set up my bench, bags, etc. and set a Birchwood Casey Shoot-n-see target with five diamonds on it at 100 yards and commenced firing.

Five round slow fire with 27 grains of 8208 yielded 1.1" for four shots with a called flyer outside of that. Let the barrel cool.

Five rounds of 27.5 grains yielded .88" for four shots with a called flyer outside of that. Let the barrel cool.

Five rounds of 28 grains was sheer ugliness at 2+". Let the barrel cool.

Five rounds of 28.5 grains was even uglier, 3+". Let the barrel cool.

For giggles I decided to sling five rounds of factory Hornady 123 grain A-max at the remaining diamond on the target and got another 3+" group. Considering that the 123 grain A-max factory load is the gold standard for the Grendel round, I thought that was a bit unusual but it's not the first time it's happened with this rifle. It apparently doesn't like the taste of the factory loads.

I've loaded up ten more rounds of the 27.5 grain loads to check one more time, but if that one looks as good the second time around as it did the first time, I guess I'm stuck loading my own. Darn...

[JASmith]

There is a possibility you will need to adjust the seating depth to get a jumo your rifle and bullet like.

Have you checked the COAL for the bullet touching the lands?

[NugginFutz]

Curious - what barrel length and profile is your BHW?

My 22" bull barrel is frighteningly accurate. My 18" Standard profile - not so much. The 22" I bought three years ago. The 18", last summer.

[Moonshine44]

There is a possibility you will need to adjust the seating depth to get a jumo your rifle and bullet like.

Have you checked the COAL for the bullet touching the lands?

No, I haven't. I loaded to magazine length.

[Moonshine44]

Curious - what barrel length and profile is your BHW?

My 22" bull barrel is frighteningly accurate. My 18" Standard profile - not so much. The 22" I bought three years ago. The 18", last summer.

It's a 20" standard profile.

[JASmith]

No, I haven't. I loaded to magazine length.

As with any troubleshooting exercise, there is wisdom in nailing one variable at a time.

A lot of noise has been made over distance of bullet jump. Assessing the COAL for bullet contact with the lands will help you determine the jump.

[Moonshine44]

So are you thinking that I may be loading just a skosh too long? Can't load any longer and have them still fit in the mag...

[JASmith]

It is possible, but more likely they need to be seated further out than your magazine allows.

Knowing that will help you decide to try a different bullet with shorter nose.

[Moonshine44]

I did load some 85 grain Sierra Varminters but haven't fired any yet. Loaded those to magazine length as well.

[NugginFutz]

My 18" BHW adores the 85 Sierra Varminters, but I didn't feel comfortable loading them to mag length, as I felt there would not be enough bullet in the case neck. At 2.210", however, the best groups are at .45 MOA, and overall groups are .75 MOA. It's a genuine pity their BC is so poor, as I really would love to use these for long range pDogs. The load of 28.4 grs H322 is wonderfully stable and accurate, but only netted 2625 fps, as higher charges opened the groups. At 500+ yards, the drop is already at 4.3 mils.

As a side note, I'm still searching for an accurate Amax or SST load for this barrel. I've had only moderate success with the Berger 130 AR Hybrids.

[Moonshine44]

Thanks for the info. I only loaded ten of the Varminters, it'll be interesting to see how those and the second set of 120 grainers with 27.5 grains of 8208 group.

[JASmith]

I did load some 85 grain Sierra Varminters but haven't fired any yet. Loaded those to magazine length as well.

Have you cycled those through the chamber to verify no land engagement while in battery?

I have also gotten outstanding accuracy with the 85 gr Varminter. The group sizes ranged from .50 moa to .60 moa with FIVE different powders. The sixth powder, W748, opened the group size up to about 1.4 moa. These all had the Magnetospeed bayonet attached, so might have been better in a hunting configuration. I will likely revisitW748 at some point.

The point is that the OAL was around 2.2" because that was about as far out as I could seat them without engaging lands. I think you'll find that's why NuggeiFutz used a length of 2.210" too.

[mike garus]

"The group sizes ranged from .50 moa to .60 moa with FIVE different powders."
Which FIVE powders?

[Moonshine44]

Have you cycled those through the chamber to verify no land engagement while in battery?

I have also gotten outstanding accuracy with the 85 gr Varminter. The group sizes ranged from .50 moa to .60 moa with FIVE different powders. The sixth powder, W748, opened the group size up to about 1.4 moa. These all had the Magnetospeed bayonet attached, so might have been better in a hunting configuration. I will likely revisitW748 at some point.

The point is that the OAL was around 2.2" because that was about as far out as I could seat them without engaging lands. I think you'll find that's why NuggeiFutz used a length of 2.210" too.

I haven't had time yet to try chambering them. I will do that carefully when I get a chance. Thanks for the information!

[JASmith]

"The group sizes ranged from .50 moa to .60 moa with FIVE different powders."
Which FIVE powders?

AR Comp, BL-C(2) CFE 223, H335, RE-7. BL-C(2) was three shots, the rest were five shot groups.