How wide are the nodes in your BRA?

[MikeMcCasland]

Hey guys,

Those of you that have multiple competitive BRA barrels under your belt, I'm curious how wide you find the nodes to be with common powders in this platform? I've been testing in .2gr increments, which works quite well with larger charges, but I almost get the impression it's a little too coarse for the BRA.

I see a larger change in elevation with .2gr increments than I do in other cartridges I'm more familiar with. Feels like it goes in/out of tune faster than what I'm used to dealing with.

Forgive me for the silly question; this is my first BRA barrel/reamer, and I usually spend my time on .308s.

Thanks,
Mike

 

[Jdne5b]

Do you mean .2 instead of .02? If .02 is too coarse, will you be cutting kernels?

 

[MikeMcCasland]

Do you mean .2 instead of .02? If .02 is too coarse, will you be cutting kernels?

Hah, yes. It's late. I'll fix it in the OP. I'm jumping in .2gr increments.

 

[BartsBullets]

In my opinion, I don’t think it’s a question of the caliber. It all depends on the barrel and powder combination. Some barrels have a huge load window others you have to be right in the load. I’ve had BRA barrels that couldn’t handle being off load by 10 feet and others that as long I was within 50 foot of the load it was competitive. I’ve seen the same thing with 6ppc barrels over the years.
Bart

 

[JFrank]

Hey guys,

Those of you that have multiple competitive BRA barrels under your belt, I'm curious how wide you find the nodes to be with common powders in this platform? I've been testing in .2gr increments, which works quite well with larger charges, but I almost get the impression it's a little too coarse for the BRA.

I see a larger change in elevation with .2gr increments than I do in other cartridges I'm more familiar with. Feels like it goes in/out of tune faster than what I'm used to dealing with.

Forgive me for the silly question; this is my first BRA barrel/reamer, and I usually spend my time on .308s.

Thanks,
Mike

I test at 500 yards in .1gr increments followed by conformation in .1gr at 1000 yards as pic below

 

[MikeMcCasland]

I test at 500 yards in .1gr increments followed by conformation in .1gr at 1000 yards as pic below

That's a pretty wide node.

 

[caihlen]

My 6 bra has a really big node. A d cup.

hahahahahah. Sorry guys. I couldn’t resist.

 

[MikeMcCasland]

Some pics for context. I was using seating depths/NT from a load I'd cooked up with Varget. Varget shot better than H4895, but I still felt like it wasn't shooting to it's full potential.

Mind you, these groups were shot prone, off a FTR bipod, in ~8-11mph 2 o'clock wind at 300 yards.

N150 shoots the tightest, but I've seen in the N150/Dasher thread, there are concerns about it being temperamental in these little cases. N150 velocities were 2855-2880 FPS at the charge range pictured.

140 seems to shoot fairly well across a broader range of charges, but it does show more vertical between the charge nodes. N140 velocities were 2896 - 2913 at the charge ranges pictured.

For context:





Here's the N140:





Going to shoot this little 6BRA at a 500 yard match this coming weekend. It's nothing serious, but I am trying to decide what powder to load up. I won't have anymore time for load dev until then. I'm leaning towards 31.4gr of N140, but open to feedback. 30.8 of N150 shoots pretty tight, and is vertically flat.

 

[JFrank]

Im just a ham & egger so probably the wrong guy to give any advice.

 

[Lefty Trigger]

Based on those picture I would lean towards the N140. It appears the N150 has a narrow window. I'm keeping an eye on this 6BRA thing because I'm currently building one....
The 31.5 group would be a winner in our 300yd varmint matches, tight groups with proper placement is key. Good job...

 

[Jdne5b]

Good stuff. I'm trying to use n140 in my PRS 6BRA and save my Varget for a picky .308 barrel if needed. 30.9gr n140 gives me 2845ish in a 26inch barrel using formed Lapua brass. 30.8-31.2 were all on the same plane at 100, and 31.4 just started to creep out the top. I've had zero time to test it at distance though.

 

[Eric Leonard]

I have 12 twist 6 BRA I shoot in UBR score I drop 8208 and haven’t weighed a charge since April but it’s somewhere around 32.7 with and 80 gr bullet at 3300 fps.
it shoots pretty good up close
Set of targets at 100 yards

 

[Falfan2017]

I’ve only had 2 bra barrels. One of them had wide nodes and I never had to change much for weather it was always consistent. This current barrel shoots smaller when it’s in tune but the window is small. Only about 20 fps from temperature change will through it out of tune and double the group size. .2 grains of powder is about it what it takes to take it in our completely out of tune. Can’t hurt to try in increments of .1 with a barrel like that.

 

[dnellans]

I’ve only had 2 bra barrels. One of them had wide nodes and I never had to change much for weather it was always consistent. This current barrel shoots smaller when it’s in tune but the window is small. Only about 20 fps from temperature change will through it out of tune and double the group size. .2 grains of powder is about it what it takes to take it in our completely out of tune. Can’t hurt to try in increments of .1 with a barrel like that.

what is the expectation for an in tune 5 shot group vs doubling the group size, vs completely out of tune?

 

[Falfan2017]

what is the expectation for an in tune 5 shot group vs doubling the group size, vs completely out of tune?

Last match in tune it agged around 2” at 600 yards in tune vs 3.5” or so agg with .2 grains too much powder. It’s done something similar at previous matches and it’s the vertical that expands so I don’t think it was just the wind blowing a couple around to expand the agg.

 

[JFrank]

Just to maintain perspective for guest reading this thread .2 grains equals about 12 kernels of Varget.

That's a lot..