Has anybody ever heard of a 308 Win modified with a longer neck?

[joshb]

We'll chalk it up to the "blind squirrel". Lucky that I saw this thread and lucky I bought a used Hunter Benchrest barreled action, a year or so ago. I searched for info but didn't find much on it. I haven't even shot it yet cause my stock isn't finished. It's a Kodiak "repeater" with a Krieger barrel. Coned bolt with magazine. It came with some fired brass and a set of custom dies. Guys have been experimenting for a really long time. Something I keep in mind when "dreaming" about a new cartridge. Prolly already been tried.

 

[JasonT]

A couple of things:
First of all a longer neck has nothing to do with improving accuracy. That is more about being able to use a variety of bullets and still being able to seat them into the rifling and with their shanks above the neck shoulder junction...that and something called the turbulence point, which again is not strictly speaking about accuracy.
Then there is the matter of the distance that you are building for. What distance? We know that for shorter distances slow twists and short bullets rule, with cases that are a lot smaller than any form of .308, and for longer distances the .308 has not been particularly competitive of late, and I seriously doubt that a sharper shoulder will magically remedy that. Last point is a question. What experience do you have with super accurate rifles? I ask this because absent that experience your musings would seem to have the requisite background experience for you to steer them in the right direction. IMO, gaining this experience should be a lot of fun, and which you would choose would depend entirely on the distance requirements. Currently the short range champ is the 6PPC and for long range the Dasher. There are others, but these will have an excellent chance of exposing you to top accuracy at their respective distances.

Thanks for that Boyd! You're right - the 308 isn't a competitive cartridge when comparing it to a 300wsm, a dasher, or a 284win. But the 308 case is really close to optimum efficiency as far as I can work out. Better yet, the barrel life (3000+) is long enough that it makes me think about trying something different. E.g. without any modifications to the case, I'm pushing a 230gr Hybrid at 2400-2500fps, which is supersonic to 1100yds+. I think with some tweaking and the ability to seat the bullet out farther, it could make hits at a mile (just for sh*ts and giggles really). I'm just thinking about the elements of accurate cartridges that do rule the road right now. Even if it's just a thought experiment, I think it's helpful for us to try and understand why things are the way they are.

 

[spclark]

And here I've been wondering whether it would be a worthwhile experiment to try something using .30" diameter bullets in a 308 case with as little neck as possible, something akin to Robert Chombart's 284 and 260INCH cartridges.

(If what you get is in French, scroll down the page to the English translation.)

Inspired by Stan Wolf's 30 Wolfpup, I fell upon these designs a little over a year ago, then had a 1:9 Brux barrel chambered with a reamer I ordered from JGS. Shooting Berger's 180 Hybrid I can safely reach 2,800 fps, effective enough to have fired a 1000 yard 200-15x late last June in the 2016 Wisconsin Individual Long Range Championship weekend at WGC.

Will have to wait to see just how long the barrel's accuracy holds up but for the time being I'm quite please!

 

[BoydAllen]

Well...let me see....doing something different without changing the case. I'll have to think about that a bit. The only thing that I could suggest is that you lengthen your throat to the point where you have just enough bullet in the neck. Without changing the case, that is about the only thing that you can do. On the other hand, if you want to play with case capacity a little, you could open a .284 case to .30 and push the shoulder back to the capacity that you want, or on the .308 case, have a reamer made to headspace like a AI, with absolute minimum body taper, and slightly oversize body diameter...sort of a .308 version of the .284 Shehane.

 

[JasonT]

Well...let me see....doing something different without changing the case. I'll have to think about that a bit. The only thing that I could suggest is that you lengthen your throat to the point where you have just enough bullet in the neck. Without changing the case, that is about the only thing that you can do. On the other hand, if you want to play with case capacity a little, you could open a .284 case to .30 and push the shoulder back to the capacity that you want, or on the .308 case, have a reamer made to headspace like a AI, with absolute minimum body taper, and slightly oversize body diameter...sort of a .308 version of the .284 Shehane.

Boyd those are some interesting thoughts! For setting a shoulder back, would you do a set back of .020", anneal, 0.020" more, etc... until you got what you wanted? And I hadn't thought about doing the 284 shehane route of the blown out case body. I do single-feed anyway...So in essence, you'd suggest something like a 284 shehane with the should pushed back a bit. Is that about right?

 

[BoydAllen]

I would not anneal until I had gotten the case into the form it would be fired in, because of the possibility of collapsing the annealed shoulder. What I was saying was that if you want a longer neck and more capacity, you will probably have to go to another case. The .284 holds about what a 30-06 does and you can fine tune capacity by pushing its shoulder back a little at a time until you have what you want. I would open it up to .30 and then start pushing back and measuring capacity at each shoulder location. For working with the .308 case, I do not think that you will be able to both increase capacity and neck length at the same time. For these sorts of experiments a case forming die with different inserts would be a great help. For pushing shoulders back a lanolin based lube is best. The original RCBS is one example.