6BR Improved or Ackley Improved Pros or Cons

[Keefe300]

Ok so I like to learn about different things and I like to try different ways of doing things. I also enjoy reading and taking to people about their experiences with different cartridges and techniques.

I have read about and played with various different Ackley Improved cartridges over the years. I also understand that an Ackley Improved cartridge has a 40 degree shoulder and an Improved cartridge for the most part has a 30 degree shoulder.

So I say all of this to lay out some ground work. My question is what are the benefits of one versus the other? Pros and Cons.

Let’s use the 6BR and 6 BRA as examples. The 6BR has an improved 30 degree shoulder and the 6BRA has a 40 degree shoulder. I know this is not an apple’s to apple’s comparison and that the 6 BRA has more case capacity and velocity than the 6BR. But if they were both equal and could achieve identical results what shoulder angle would work best?

Does a 40 degree shoulder have less bolt thrust? Does the brass grow less? Does it have a wider tune window? Less throat erosion? Do the gases flow better from the case?

I am looking for some insight into this with possibly some data to back it up. I know there are people out there that have pushed the 6BR to extremes and in reverse there are guys shooting 6BRA’s at BR levels.

I am trying to figure out if there is a combination of case capacity, length, shoulder angle, etc that just makes a cartridge shoot better.

 

[gunsandgunsmithing]

Ok so I like to learn about different things and I like to try different ways of doing things. I also enjoy reading and taking to people about their experiences with different cartridges and techniques.

I have read about and played with various different Ackley Improved cartridges over the years. I also understand that an Ackley Improved cartridge has a 40 degree shoulder and an Improved cartridge for the most part has a 30 degree shoulder.

So I say all of this to lay out some ground work. My question is what are the benefits of one versus the other? Pros and Cons.

Let’s use the 6BR and 6 BRA as examples. The 6BR has an improved 30 degree shoulder and the 6BRA has a 40 degree shoulder. I know this is not an apple’s to apple’s comparison and that the 6 BRA has more case capacity and velocity than the 6BR. But if they were both equal and could achieve identical results what shoulder angle would work best?

Does a 40 degree shoulder have less bolt thrust? Does the brass grow less? Does it have a wider tune window? Less throat erosion? Do the gases flow better from the case?

I am looking for some insight into this with possibly some data to back it up. I know there are people out there that have pushed the 6BR to extremes and in reverse there are guys shooting 6BRA’s at BR levels.

I am trying to figure out if there is a combination of case capacity, length, shoulder angle, etc that just makes a cartridge shoot better.

Lots of things way more important to worry about to shooting well, given the same speeds. I think all the things you mentioned are very subjective and difficult, if possible, to actually quantify in the real world. Even if they were all true, I'll take the one with the better bbl. Lol!

Practice well, and practice often. Practice in bad conditions and always use flags. Learn to recognize tune and how to fix it, and have fun practicing. Did I mention Practice.

 

[Dave Zander]

My experience is with the 6BRA. Been shooting it about 12 months. about 2300 rounds so far Just changed out barrel.105-112g bullets. H4895. All I can say is the brass doesn't seem to grow, never trimmed after initial fire forming, primer pockets hold up, started with 300 cases , haven't scrapped any except the ones I occasionally screw up. I shoot it in the 2850 fps range with Lapua 6BR brass . Never Ran the straight 6BR but I really like the 6BRA.

 

[gunsandgunsmithing]

My experience is with the 6BRA. Been shooting it about 12 months. about 2300 rounds so far Just changed out barrel.105-112g bullets. H4895. All I can say is the brass doesn't seem to grow, never trimmed after initial fire forming, primer pockets hold up, started with 300 cases , haven't scrapped any except the ones I occasionally screw up. I shoot it in the 2850 fps range with Lapua 6BR brass . Never Ran the straight 6BR but I really like the 6BRA.

I do think stretch, or lack of it, is the easiest on his list to quantify but mild loads and good die to chamber relationship and we might be so close it's hard to see a difference. I agree the AI should benefit a bit from the straighter case and maybe the shoulder angle as well..if all else is equal. Don't get me wrong, I like my Ackleys.

 

[Keefe300]

Lots of things way more important to worry about to shooting well, given the same speeds. I think all the things you mentioned are very subjective and difficult, if possible, to actually quantify in the real world. Even if they were all true, I'll take the one with the better bbl. Lol!

Practice well, and practice often. Practice in bad conditions and always use flags. Learn to recognize tune and how to fix it, and have fun practicing. Did I mention Practice.

I must say I agree with you the better barrel and tune are very important. Practice and learning wind flags also helps.

 

[Keefe300]

I do think stretch, or lack of it, is the easiest on his list to quantify but mild loads and good die to chamber relationship and we might be so close it's hard to see a difference. I agree the AI should benefit a bit from the straighter case and maybe the shoulder angle as well..if all else is equal. Don't get me wrong, I like my Ackleys.

See I picked the 6BR vs 6BRA because if you look at the reamer print the body taper is basically identical. The only major difference is the shoulder angle.

There is one thing for sure though if you put an Ackley Improved case new to any parent case the Ackley just looks good.

 

[R.Morehouse]

Pro vs Con ?
You can compete at the 6BR distances fire forming for your 6BRA, then go play at 1K if you choose to. The 6BR IMHO just does not quite have enough ass to compete at 1K, unless you can find a way to push the 105 class bullets at 3060ish safely....When I was shooting the BRA it liked RL15 the best here in the western Pa. shooting season.

Regards
Rick

 

[gunsandgunsmithing]

See I picked the 6BR vs 6BRA because if you look at the reamer print the body taper is basically identical. The only major difference is the shoulder angle.

There is one thing for sure though if you put an Ackley Improved case new to any parent case the Ackley just looks good.

I know that too but your post was about hypotheticals and you specifically mentioned Ackley more than once. A 6 BRA isn't a true AI case. So I was supposed to assume you knew this? Also, you can affect case stretch in other areas as well. Take a look at the Beggs cartridges, basically a 220 and 6mm Russian, for example. Tons of body taper and very shallow shoulder angle of 21.5°. They still stretch some ime but are improved in that regard via a .060 radius change at the neck/shoulder junction. The logic being the sharper junction stops or slows forward flow of brass there. I won't disagree that a steeper shoulder plays some role in brass flow too. I'll contend that the sizing die to chamber relationship is the biggest factor here but not the only factor. Pressure is another one. I wasn't playing games with terminology and was specific about AI cases in my post, but I should've been more specific that a BRA isn't a true AI, too. Ultimately, and in reality, both are excellent but the BRA has a little more horsepower with typical loads. Your hypothetical was loading mild with both. Good die fit and mild loads and brass stretch is a non-starter with both, imho. The downsides to me would be fire forming and dies but neither are deal breakers. Tunability can be argued to some degree and some feel a straight 6BR is almost as easy as it gets in that regard. I don't think anything is as easy as a 30BR or 30 Major to tune though.

 

[Liven The Dream]

I am speaking Prone Target Rifles.
I had a 6BR Never Shot past 600 yards 107 MK. It was a Hammer.
Theses days two 6 Norma Dashers ( Brass available No Fire Forming ). They are F/Open Rifle
F/Class smaller Target rings.
With easy loads with 105HB 1000 yards is workable, wind reading and Skill help.
Want to try Bart's Bullets one day.

Best of Luck

 

[Dave Zander]

Alpha Munitions has 6BRA Brass. I just bought some as a backup to the Lapua.
Fire forming the Lapua 6BR into BRA is simple and accuracy is just as good as the formed brass really, my experience.

 

[Keefe300]

I know that too but your post was about hypotheticals and you specifically mentioned Ackley more than once. A 6 BRA isn't a true AI case. So I was supposed to assume you knew this? Also, you can affect case stretch in other areas as well. Take a look at the Beggs cartridges, basically a 220 and 6mm Russian, for example. Tons of body taper and very shallow shoulder angle of 21.5°. They still stretch some ime but are improved in that regard via a .060 radius change at the neck/shoulder junction. The logic being the sharper junction stops or slows forward flow of brass there. I won't disagree that a steeper shoulder plays some role in brass flow too. I'll contend that the sizing die to chamber relationship is the biggest factor here but not the only factor. Pressure is another one. I wasn't playing games with terminology and was specific about AI cases in my post, but I should've been more specific that a BRA isn't a true AI, too. Ultimately, and in reality, both are excellent but the BRA has a little more horsepower with typical loads. Your hypothetical was loading mild with both. Good die fit and mild loads and brass stretch is a non-starter with both, imho. The downsides to me would be fire forming and dies but neither are deal breakers. Tunability can be argued to some degree and some feel a straight 6BR is almost as easy as it gets in that regard. I don't think anything is as easy as a 30BR or 30 Major to tune though.

Thanks for your clarification and insight. I was not thinking about it the whole way through. The 6BRA has the Ackley shoulder but no straightening of the body so therefore is not improved. Well other than the shoulder angle and body shoulder junction being blown forward.

But now I will be reading about the Beggs cartridges. Lol

 

[urbanrifleman]

The 6bra is the better 6br.

 

[Tommie]

If a heavily tapered case is given the Ackley treatment there will usually be less bolt thrust. 22-250 is a prime example. With the BR case that’s basically gonna be a moot point. I’ve found (as already mentioned) that case growth almost goes to a stand-still with a sharp shoulder. Really the BR in Ackley form is going to allow an extra trickle or two of powder in the case. If that’s important to you, so be it.

 

[Tesoro]

The 6bra is the better 6br.

But are you? I am not.

 

[urbanrifleman]

But are you? I am not.

 

[gunsandgunsmithing]

If you go back and read this thread, it clearly states light loads, which negates possibly any benefit of the BRA over the std case. Case stretch becomes negligible with light loads and proper die fit. Just my 2 cents. I'm not saying one is better than the other, especially not under the op's stated parameters. Under real world parameters, the BRA certainly has a small speed advantage and likely in terms of stretch also, but those aren't the stated parameters. Kinda like loading a 280 AI vs a 7 ?mag, both loaded way below eithers potential. But loaded to their limits, the rules change.

 

[JEFFPPC]

In this endless debate, which particular cartridge you pick I would say is the least,by far, component of the entire package needed to compete. Pick one, learn it, ride with it.

 

[dgeesaman]

Alpha Munitions has 6BRA Brass. I just bought some as a backup to the Lapua.
Fire forming the Lapua 6BR into BRA is simple and accuracy is just as good as the formed brass really, my experience.

You do bring up one advantage of 6BRA: more brass options. You can fire form any of the 6BR or buy 6BRA brass.