308 Winchester 40degree Ackley

[Stan Taylor]

I see a lot of 260 Ackley. an 6.5 Ackley any one ever tried in 308 Winchester Ackley.
Would like to here the pro's an con's.

 

[Paddyd]

I ask the same question and all I get was it wouldn't help enough to be worthwhile. Why that may be I have no idea.

 

[Doug Beach]

The capacity difference between a .260, and .260AI is not great. Your velocity difference would be much smaller than, say, the difference between .308 & .30-06. Case life would probably be improved.

 

[Paddyd]

I think it would be hard to improve on the 308W as it is so easy to find multiple good shooting loads with, but if it would lessen the chore of trimming cases it might be worth it. I really would like to see a real world comparison between the two.

 

[Kurz]

Looking at the example below, you see that the difference between the shoulder and neck diameter is fairly small especially when compared to the .260 Rem or .243 Win. The powder capacity gain is minimal but the 40 degree shoulder does retard case growth, lessening trimming.

Often the balance between making the improved case or leaving it alone makes the choice for most folks. Saving case life, barrel life and components often times convinces us of the necessity of being frugal.

 

[STOMP442]

With the .260 Ackley being one of my favorite cartridges and building a handful of them over the years I can say the increase in velocity is somewhere around 150fps. I have a couple standard .260s as well and they all seem to want to shoot right around the 2800fps mark. The Ackley will get you into that 2950 node of the 6.5-284 while having excellent brass life and use less powder to do it. I would imagine the .308 would see similar results giving you .30-06 performance or very near it in a smaller more efficient package with very little case prep beyond your initial fire forming. I love Ackley cartridges.

 

[mikeeg02]

With the .260 Ackley being one of my favorite cartridges and building a handful of them over the years I can say the increase in velocity is somewhere around 150fps. I have a couple standard .260s as well and they all seem to want to shoot right around the 2800fps mark. The Ackley will get you into that 2950 node of the 6.5-284 while having excellent brass life and use less powder to do it. I would imagine the .308 would see similar results giving you .30-06 performance or very near it in a smaller more efficient package with very little case prep beyond your initial fire forming. I love Ackley cartridges.

And with rl26 in a 260 ackley you can push the 140s at 3100 lol. I found an accuracy node there. No pressure whatsoever. (SRP alpha cases) Once I chronographed it and realized it was going that fast I backed it down because I know better to the ~2950 range.

 

[STOMP442]

I couldn't get R26 to run for me. Once I had about five rounds down the tube and things started to warm up pressures increased dramatically and primers would blow and trash my cases. Had the same problem in a couple Creedmoors I tried it in as well.

 

[Terry]

Imagine if people had said the same thing about the 6BR and the 6BRA.

 

[XTR]

1. it's not going to be legal for anything that requires a 308 for competition
2. 308s don't grow much anyway. I think I may trim my F-TR brass once in it's lifetime?
3. nobody really uses 308s for competition beyond the things that require it
4. The gains for doing an AI on any 308 based case are really small. Even the big jump from 308 to 30-06 only nets ~150FPS, so going to the trouble to fire form for a potential 50FPS. Deer can't tell the difference.

 

[mikeeg02]

I couldn't get R26 to run for me. Once I had about five rounds down the tube and things started to warm up pressures increased dramatically and primers would blow and trash my cases. Had the same problem in a couple Creedmoors I tried it in as well.

I never tried extended strings at 3100 fps, but a couple 5 shot groups before I borrowed a chronograph and I found how fast it was. I shot most of an 8# jug at ~2950 with it all this year at ridgway (850-1k silhouettes) and couldn't believe how well it shot. Even with varying temperatures. There was no sign of pressure at the higher node for me.

Maybe when you load it and get extreme velocity out of it, it does become more inconsistent and run into issues like you've described. I have heard of others finding it temperature sensitive, but again, they may have loaded it so hot, because when they tested it, there wasnt any pressure.

I had initially load developed in the 45* range, and shot until july with that load. Then it hit the 80s, and I did some testing at 300 with it, and found it opened up a little at 300y. I backed it off .4 grain and found it closing back up again, but the most interesting thing, was POI on the target had not changed. So while the 40 degree swing affected accuracy slightly, it didnt seem to affect POI. I also tested this at one of the matches and shot half of the match with the original load of 46.6 and reduced load 46.2 grains. By this time the barrel also had over 800 rounds through it. Thing is still a hammer.

 

[msinc]

Maybe a good way to explain it is that the case capacity gain has to be enough to really warrant doing it. In example, the 30-30 Winchester is a "recommended" cartridge to improve. With it's low angle narrow shoulder case capacity from the improved version is considerable. You also must remember that how a cartridge headspaces is a big consideration too as to whether or not the end result will be "worth it". The 30-30, again, not only blows a shallow shoulder way out to very near straight sides, but there is another bonus gain in the fact that the neck to shoulder junction can also move forward because that junction is not being used for headspace purposes.
Now consider the 308...kind of has big shoulders already and not too bad of a shoulder angle. We cant move the neck to shoulder junction anywhere because we use it to headspace. There is a gain, but not much with that big diameter bullet, and not enough to worry about especially before the advent of Reloder 26. That may be subject to change if Alliant ever decides to go ahead with throttle up and load some shelves with it. "trickle down economics" don't work too good with a fantastic powder!!!
Some cartridges are just not done for other reasons. The 300 H&H...why not just shoot a 300 Win Mag?? The 270 Winchester has never been recommended because for the case size and the bullet diameter/weight it's already over square enough. I consider the 243 in the same boat. 30-06 Springfield, highly recommended because, again, that weak shoulder and heavier bullet. Again, some of the ones that were not so good might change with better and better gun powder.

Edit: the above reasoning doesn't include all the issues....at some point pressure becomes a serious consideration. You still have to maintain some safety margin. At first glance the 223 would seem like not too good a candidate, but we know better. In the case of the 223 it being a small bullet, it doesn't take much powder increase to add considerably to the performance.

 

[284winner]

With the .260 Ackley being one of my favorite cartridges and building a handful of them over the years I can say the increase in velocity is somewhere around 150fps. I have a couple standard .260s as well and they all seem to want to shoot right around the 2800fps mark. The Ackley will get you into that 2950 node of the 6.5-284 while having excellent brass life and use less powder to do it. I would imagine the .308 would see similar results giving you .30-06 performance or very near it in a smaller more efficient package with very little case prep beyond your initial fire forming. I love Ackley cartridges.

I believe from a past experience with an aqaintance that had a 308 AI the difference was about 50-75fps from an 06. Closer to the 50 fps. It's a cool looking little cartridge when you ackeyize it.

 

[Nature Boy]

It's a cool looking little cartridge when you ackeyize it

It does look neat. That alone makes me want one

 

[cmillard]

Go for it!! I would run it in a long action though and load bullets long so you can run in magazine and get more case capacity