Why 6 BRA?

[JohnMill]

I agree with you for sure. For me, it's easy to make sense out of both views. I'd like to see a real study by metallurgical standards tell us the truth.

I believe that if someone were to dredge up the Precision Shooting article on Turbo Point chamber design, it might answer any or all/some of those questions

 

[Alex Wheeler]

I didnt know you were into antique camera equipment.

 

[urbanrifleman]

It's a cellphone picture of the display screen. Don't have any fancy stuff, spent all my money on gunsmith bills!

Tom

What are we seeing?

 

[johnnyi]

What are we seeing?

I'm assume the first photo are from the dasher with very early sighs of wear (if you can see those lateral lines) at the start of the throat just in front of the case mouth. vs the second photo looks like a freshly cut chamber which I assume is the BRA. Yet he is saying they have the same number of rounds down the bore. Early indications favoring the BRA in barrel wear...?

 

[urbanrifleman]

On the left, is that firecracking?

 

[Alex Wheeler]

The vertical line is the chamfer at the end of the neck at the beginning of the free bore. The neck is to the right and the freebore is to the left of this line. That saw edge look on the top picture is erosion starting in the throat. Thats a very big difference to see that early on.

 

[daniel brothers]

I can't tell if it's a boy or a girl... need better glasses I guess.

 

[Toby Bradshaw]

I can't tell if it's a boy or a girl... need better glasses I guess.

 

[comagutsa]

Pretty interesting to watch the barrel speed up like that huh? One of our local shooters mapped a couple new Kriegers with every shot over the lab radar for the first 150. It was cool to see the velocity curve as the barrel sped up. Theres only one barrel I know of that does not speed up and you can do load development on day 1, but they wont tell me what grit they use to lap them or I be re-lapping our Kriegers I have to believe its in the surface finish.

i used lab radar on my 6BRA barrel from 1st shot.. started at 2751fps , 120 rounds later I'm at 2820fps

 

[CaptainMal]

Not so sure Tom...

105 rds total of fire forming and maybe 40 test rds. on Alex's new BRA build for me:
ZX4m9moaRFiBhMIZvflefg by Larry Malinoski, on Flickr

Happy and sad because of you...

PICT0058 by Larry Malinoski, on Flickr

Look at the carbon build-up in front of the leade at the end of the throat. Sad to see this but happy you motivated me to look with my borescope. There does seem to be a bit of leade edge wear but nowhere as nasty as with my Dashers. Oh - I just used some CLR and BoreTech CR-4 to clean it out. Here's the same only after cleaning.

PICT0060 by Larry Malinoski, on Flickr

You can see a teeny bit of edge wear starting. I can form no conclusions about throat wear with BRA from this single example.

 

[Alex Wheeler]

Larry, thought you had a BR scope?

 

[johara1]

Larry, thought you had a BR scope?

LMAO......... Jim

 

[CaptainMal]

"Larry, thought you had a BR scope"?

I have multiple BR scopes and that Competition plus many other brands also. Comp just returned from Nightforce as OK ... but noticed new turrent knobs on it. It will be on Steve's scope checker as soon as both he and the weather cooperate.

 

[Alex Wheeler]

I thought you made people sign something?

Thats the secret to "why BRA"

 

[urbanrifleman]

Forgive my ignorance but I would say that "wear" is what we all call the barrel breaking in.

 

[BOB LEE SWAGGER]

So... Using the AW reamer print is (which? 2.5 or 3) the Harrell's Dasher die with .082 off the bottom the deal with a Forster Co-Ax?

 

[maddysdad]

if you look up in one of the old rifle magizines there was a article about the 6 x 45 br they used 308 cases and formed them with a 45 degree shoulder.they had 2 barrels,1 a 14 twist another a 12 twist they used 80 grain bullets at 3000 fps out of a 24 inch barrel.except for the shoulder the 6mm bra is close to the one that jim shoots I would say.
gary