Why 6 BRA?

[Terry Altom]

Count me in the latter. I believe barrel wear is a function of heat and duration, aside from barrel attributes. I may be wrong but all I've seen in regard to this is theoretical. I would like to be proven right or wrong by something more scientific, though.

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.

 

[JohnMill]

This could be to mean.... how about
6MM BRO - JOB

Now you're just being sirry

 

[4xforfun]

Flame convergence point. With a dasher its in the throat, with a BRA its in the neck. It certainly is proving out to move slower. Which in it self makes it easier to stay in tune.

Stirring the pot....but......since brass is considerably softer than steel, and the melting point of brass is considerabley less, also, wouldn't we see erosion in the brass necks?

Tod

 

[Sheldon N]

Stirring the pot....but......since brass is considerably softer than steel, and the melting point of brass is considerabley less, also, wouldn't we see erosion in the brass necks?

Wouldn't the erosion be spread out over all pieces of brass? If you had 100 cases, the amount of erosion in any one case would be 1/100 of the amount of throat erosion?

 

[Alex Wheeler]

Stirring the pot....but......since brass is considerably softer than steel, and the melting point of brass is considerabley less, also, wouldn't we see erosion in the brass necks?

Tod

Im not an expert on how a throat erodes. However I picture it like an oxy/acy torch effect. Cant cut brass with a torch, but you can melt it. Either way, throats do move slower in the BRA, not that thats very important to me. Its all about accuracy and agging ability. Thats why Im such a fan of the case. All you have to do is chamber 50 dashers and 50 BRAs and get the feed back. It will be clear as day.

 

[4xforfun]

Wouldn't the erosion be spread out over all pieces of brass? If you had 100 cases, the amount of erosion in any one case would be 1/100 of the amount of throat erosion?

Maybe.....but you didn't take into account that brass is much softer and has a much lower melting point, which means it should erode much faster than BBL steel. So, that 1/100th = ....What?

Tod

 

[Raythemanroe]

Maybe.....but you didn't take into account that brass is much softer and has a much lower melting point, which means it should erode much faster than BBL steel. So, that 1/100th = ....What?

Tod

Then again, brass isn't getting to temps a barrel does running ten - twenty rounds in a few minutes.. Well, unless you are a fast reloaded..


Ray

 

[gunsandgunsmithing]

Maybe.....but you didn't take into account that brass is much softer and has a much lower melting point, which means it should erode much faster than BBL steel. So, that 1/100th = ....What?

Tod

...and won't all of that abrasive powder that hits the neck, at the "convergence point", make the necks really thin? Better stop cutting "thin to win", and make them thick as a brick. No need to anneal...Brass hasn't been work hardening....It's been losing neck tension as it wears thinner. Just drop down on bushing size and sell the annealer.

Ya'll help me out here. I'm running out of ideas that support the theory of shoulder angles and neck lengths saving barrels. Lol! Who knows? Maybe they're right but I'm gonna keep believing that heat and duration are the main culprits..until they test some 180° shoulders. Now THAT just might save barrels. Lol!

 

[Alex Wheeler]

...and won't all of that abrasive powder that hits the neck, at the "convergence point", make the necks really thin? Better stop cutting "thin to win", and make them thick as a brick. No need to anneal...Brass hasn't been work hardening....It's been losing neck tension as it wears thinner. Just drop down on bushing size and sell the annealer.

Ya'll help me out here. I'm running out of ideas that support the theory of shoulder angles and neck lengths saving barrels. Lol! Who knows? Maybe they're right but I'm gonna keep believing that heat and duration are the main culprits..until they test some 180° shoulders. Now THAT just might save barrels. Lol!

Convergence point is one idea. Barrel life is so far down the list of things I think about I dont have a firm opinion on it either way. All I know is they do move slower in the BRA than a dasher, I doubt its the 1.2 grains less powder making the difference but who knows.

 

[Grimstod]

Or better yet, someone figure out WHY it shoots better. I know it's not strictly capacity because I've been there before and went right back to dashers.

Tom

My Guess is that because it has a longer neck the donought zone is far enough back that bullets do not get seated into it. Mike Ratigan attributed this cause alone to be the reason the 6PPC shoots so well.

 

[Grimstod]

We dont seat dashers that deep either

I have seen a lot of loaders that do. They just do not know any better. BRA is dummy proof

 

[BoydAllen]

All other things being equal, rate of fire has a lot to do with throat damage. Cases conduct the heat to this large head sink that they are chambered in, and they are ejected after firing. Barrels, especially those used for long range benchrest are routinely subjected to rapid strings of fire that build throat temperature. On the neck length thing. Do some asking around about the 6mm Remington vs. the .243 Winchester on barrel life.

 

[Sheldon N]

I suppose another way of thinking of it rather than as some sort of angular flame point convergence, is to ask the question "Where the powder is located in the brass/barrel when it ignites?". In a straight walled pistol size case the powder closest to the primer ignites first and starts to launch both the powder ahead of the already burning powder plus the bullet down the barrel. The more the case is a bottleneck shape, the more it restricts the powder from being launched down the bore before it is fully burned. Case like the 243 Win would allow a good chunk of burning powder to be launched into the throat, where as a 40 degree shoulder case with a shorter/fatter powder column and a longer neck is going to help keep that powder burning inside the case.

 

[Jet]

Fire formed 95 pieces of brass with 29.9 gr of Varget, BR400 primers and Berger 108s seated to just touching. Did a barrel break in process on a new Krieger at the same time for the first 40 or so rounds. Shot at 100yds and the wind was switching back and forth a good bit so I didn't really attempt to shoot anything small. The group below is when the wind settled down and I watched the flags. .3" for 12 shots. As a side note. Velocities stayed steady for shots 3-45 then climbed a few fps every few rounds up to shot 80 then it settled down for the last 15 shots. Ended up 50 fps faster when I finished. Looking forward to getting some load testing done.

 

[Alex Wheeler]

Fire formed 95 pieces of brass with 29.9 gr of Varget, BR400 primers and Berger 108s seated to just touching. Did a barrel break in process on a new Krieger at the same time for the first 40 or so rounds. Shot at 100yds and the wind was switching back and forth a good bit so I didn't really attempt to shoot anything small. The group below is when the wind settled down and I watched the flags. .3" for 12 shots. As a side note. Velocities stayed steady for shots 3-45 then climbed a few fps every few rounds up to shot 80 then it settled down for the last 15 shots. Ended up 50 fps faster when I finished. Looking forward to getting some load testing done.

View attachment 1027700

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.

 

[1911mag]

Question has anyone built one on a Bartlien 5R barrel and have had sucess? Not opposed to other brands just favor that barrel from past sucess.

 

[Jesse Gietzen]

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.

our engineers are experimenting with different lapping grits right now, as well, although likely for different reasons. i have two guesses as to which barrel manufacturer you're referring to, but am curious. i think you may be right about surface finish.

 

[Steelnecktie]

I’d guess Rock Creek.
I’d like to know if surface finish has something to do with cold bore shot. Seems like the Proof Research carbon barrels hold a pretty good cold bore shot compared to other barrels.

 

[Alex Wheeler]

I have lapped barrels with 80-180 AO and SC grits. If you bore scope new barrels during the break in process you will see a very obvious change in the surface finish. Especially on the tops of the lands. I am not sure the original lapped finish plays a huge role after the barrel has broken in. I have never had a coppering problem, but I have not gone finer yet. I think volume plays a bigger role in coppering. Some barrels never see a lap and seem to be ok. I dont think Douglas laps.

 

[JohnMill]

I always call Ackley improved cartridges Ackley's like I am sure a lot of others do. Tom actually started calling it the bra, I always called it the br ackley. The bra seemed to stick. So I guess @tom is the knucklehead.

I always appreciated Ackley's pioneering ( I think ) And the same for Alex Wheeler. Hope to buy something from you someday