6BR- Ackley Improved 40 degree

[SHall]

Has anyone ever experimented with just blowing out the shoulder of a standard 6BR to 40 degrees? No, I'm not talking about a Dasher or BRDX where the shoulder is blown forward 70-100 thou and has a 40 degree shoulder. My winter project is an Improved 6BR that has the Ackley benefits, but much easier to make than the existing improved BR's. P.O. Ackley's theory with the 40 degree shoulder and very little body taper was: better combustion chamber, more stable brass, less bolt thrust, less case growth, more velosity with less pressure. This Ackley Improved round will headspace on a new standard 6BR (Lapua) case at the neck/shoulder junction. So, there is no case prep. hassles associated with blowing the shoulder forward. There is safety issue with blowing the entire shoulder forward: this is case stretch. If not fireformed correctly, the case can stretch at the web, leaving it thin in that area. A thin web can rupture and blow brass, powder, and hot gasses back in the face of the shooter. I have witnessed this first hand: it is not pretty. If anyone can shed some light on this experiment let me know. And if you or know of someone that has a reamer or dies for this animal let me know. Thank you, Samuel Hall

 

[Chappy]

Sounds like something fun to mess with. Would probably do exceptionally well in 600 yard comps, but what do I know.

 

[johara1]

Sam, run a .460 40degree shoulder and you can use a Dasher die cut off about .100. Maybe run a Dasher reamer in short….. Sounds like a winner ……… jim

 

[tclaunch]

Sam, you may have met David Dorris when attending the nationals here in Memphis. I think now he has also been to Piedmont, anyway he has played with success the design you mention. He would be a good one to ask. He uses 2 reamers to get this done, similar to Jims suggestion.

 

[Ggmac]

I've got a few . I shoot short range with them and found no great improvement over the std 6 br . I had a reamer made which allows me to go in and make a dasher or stay short . I should see what it'll do at longer than 300 but too long of a drive .
I've got the 6 x06 Ackley ,6x 08 ackley , 6 mm rem ackley , 6 BR Ackley ,
Too much time , enjoyed on the lathe . Have only shot the 6 br Ackley and dasher.
6 TCU is a go to gun when I don't want to spend time reloading , it is very forgiving.

 

[Ackman]

Try it and see. But that short 6BR case already has about-AI body taper, and an AI shoulder diameter. I doubt that blowing the shoulder out another 10deg will do much. The Dasher or BRX are a whole different thing though.

 

[SHall]

James, I took a 6BRDX (40 degree shoulder) and ran it in short to an existing 6BR chamber to make the 40 degree shoulder. The BRDX is .462 at the shoulder. It cleaned the chamber up perfect! I fireformed 7 pieces of brass initially (and zeroed my scope). Full 6BR loads of R-15 and Hybrids at 100 yards. Result: 1st three fouling the barrel shot a small clover leaf under .2, then the next four I could not tell where they went because went through the center. I then loaded some fireformed brass to do a ladder test at 500 yards. I worked loads up to a grain of R-15 over the standard 6BR load. That load chronographed at 3044fps with no pressure signs at all! Now, that is a 31 inch barrel. Jackie Schmitz's test with a 6BR showed an average loss of 8fps per inch. Taking that into account, a 28 inch barrel would be shooting 3020fps. That is right there with the Dasher/BRX. This may just be a fast barrel? It is also shooting as good at 500 yards, maybe better than anything I have tried so far. Time will tell. I am trying not to get my hopes up too much yet. But I like what I see so far!

 

[savagedasher]

I think it would be great. With Varget and Rl 15 or other fast powders like them.
I like H4350 the smaller case wont work. My new case is a Dasher .020 long..
Larry

 

[johara1]

Sam, what was the case length after Fire forming? jim

 

[johara1]

I think it would be great. With Varget and Rl 15 or other fast powders like them.
I like H4350 the smaller case wont work. My new case is a Dasher .020 long..
Larry

I tried H4350 again today in the Dasher, used a 12" drop tube. 36.3 still had vertical and was under 3000 in two different barrels. I think i'm getting close but what a pain…… jim

 

[Changeling]

[ I tried H4350 again today in the Dasher, used a 12" drop tube. 36.3 still had vertical and was under 3000 in two different barrels. I think I’m getting close but what a pain…… Jim
[/quote]

Jim, want length barrel and bullet were you using?

 

[savagedasher]

I think it would be great. With Varget and Rl 15 or other fast powders like them.
I like H4350 the smaller case wont work. My new case is a Dasher .020 long..
Larry

36.6 is what I load. Larry



I tried H4350 again today in the Dasher, used a 12" drop tube. 36.3 still had vertical and was under 3000 in two different barrels. I think i'm getting close but what a pain…… jim

 

[dmoran]

I think it would be great. With Varget and Rl 15 or other fast powders like them.
I like H4350 the smaller case wont work. My new case is a Dasher .020 long..
Larry

Larry -
Kyle Brown set a 1000-yard World record (10-shots) with a 6mmBR with H4350 & 105 AMax's, some years back.
I know of no records shot with a 6Dasher from H4350.
Donovan

 

[dmoran]

I tried H4350 again today in the Dasher, used a 12" drop tube. 36.3 still had vertical and was under 3000 in two different barrels. I think i'm getting close but what a pain…… jim

Jim -
I almost always get respectable accuracy from H4350 in my 6Dasher barrels, but not as good as with RL15, Varget, H4895.
Like your seeing, always a little more vertical with it.
I do get the upper velocity levels, from most Lots.
But have seen some big variations in Lots to speed (Matt told me he has as well).
Maybe you got a "slower" burning Lot.
Donovan

 

[johara1]

[ I tried H4350 again today in the Dasher, used a 12" drop tube. 36.3 still had vertical and was under 3000 in two different barrels. I think I’m getting close but what a pain…… Jim

Jim, want length barrel and bullet were you using?
[/quote]



Two different barrels both were 28" both were shooting over 3000 with RL- 15….. jim

 

[johara1]

I tried H4350 again today in the Dasher, used a 12" drop tube. 36.3 still had vertical and was under 3000 in two different barrels. I think i'm getting close but what a pain…… jim

Jim -
I almost always get respectable accuracy from H4350 in my 6Dasher barrels, but not as good as with RL15, Varget, H4895.
Like your seeing, always a little more vertical with it.
I do get the upper velocity levels, from most Lots.
But have seen some big variations in Lots to speed (Matt told me he has as well).
Maybe you got a "slower" burning Lot.
Donovan

Donovan, That could be, I have one old lot and one new one. i was using new one. Still trying to get away from RL-15 but it is so uniform lot to lot and it still always shoots the smallest groups…….. jim

 

[Changeling]

Hi Sam, I've been wondering if you have worked with your 6BR-AI40* any more since your last post? I found your idea very interesting and would really like to see any new progress on the subject when you find the time. 8)

 

[stansrifles]

I shot sams verison of Ackley improved today it averaged 3.1 for 4 targets at 600yds condition was terrible.
Stan

 

[birdog]

Sam, I want one

 

[Changeling]

I shot sams verison of Ackley improved today it averaged 3.1 for 4 targets at 600yds condition was terrible.
Stan

Hello Stan, would you mind posting your load data?