Why not .338 LM Ackley Improved?

[jfields]

If you are trying to send a 300 grain Berger or Scenar or Matchking, etc. as fast as possible without going to the larger bolt diameter of the .375 or .408 cases, is the .338 AI not the way to go?

I know you are going to have the headache of fire forming your brass, but what other downsides are there to going this route? Is there going to be diminished barrel life compared to a standard LM barrel?

I have been thinking about this for a while and would like to know what people who know something about it think.

Thanks!

-J

 

[Dogtown]

I'm giving that a try right now. Originally I was working on moving up from a 26" 1:10 twist barrel to a 32" 1:9.5 twist barrel hoping to get more velocity. Now I'm switching gears and getting a .338LM Improved reamer from JGS to chamber a 34" progressive 1:10-9 twist Bartlein barrel. Yeah, fireforming is annoying, but if I can get a 300 Scenar to 3100fps I'll be really happy. I would have considered .338 SnipeTac instead as obviously there's more powder volume and velocities approaching 3400fps are possible, however that would require a completely new rifle whereas I can just swap out .338 barrels on my SRS. Besides, moving up to a .408-based bolt I think would warrant a shift to .375CT anyway.

ETA: I got a lot of good info from JeffVn. He pointed out that there are a few different variations on this spec floating about, so make sure that you a reamer and dies that match accordingly.

 

[kass]

I'm giving that a try right now. Originally I was working on moving up from a 26" 1:10 twist barrel to a 32" 1:9.5 twist barrel hoping to get more velocity. Now I'm switching gears and getting a .338LM Improved reamer from JGS to chamber a 34" progressive 1:10-9 twist Bartlein barrel. Yeah, fireforming is annoying, but if I can get a 300 Scenar to 3100fps I'll be really happy. I would have considered .338 SnipeTac instead as obviously there's more powder volume and velocities approaching 3400fps are possible, however that would require a completely new rifle whereas I can just swap out .338 barrels on my SRS. Besides, moving up to a .408-based bolt I think would warrant a shift to .375CT anyway.

ETA: I got a lot of good info from JeffVn. He pointed out that there are a few different variations on this spec floating about, so make sure that you a reamer and dies that match accordingly.

Don't worry, you shouldn't have any issues hitting mid 3100 with the improved and a long barrel, I don't anyway. As for fire-forming, make sure the chamber is cut correctly for a snug shoulder/neck junction contact in chamber on bolt closure ( virgin case ), load away and have fun, they will shot great.

 

[excaliber]

There is faster 338`s with the same boltface as the 338 Lapua. Think rebated rim. Fatter body than Lapua with same size rim. Also same case length. Still in testing.

 

[Dirty D]

There is faster 338`s with the same boltface as the 338 Lapua. Think rebated rim. Fatter body than Lapua with same size rim. Also same case length. Still in testing.

Sounds like a scaled up .284Win case.

 

[azsugarbear]

Kirby Allen's 338 Allen Express is close to what you are talking about. Doesn't quite get to 3100 fps, but does tend to max out the 338 lapua case. He does more than just "ackley-ize" the case. He blows out the side walls a little more; improves the shoulder angle; and moves the shoulder forward. here is a link to his modified 'Express' line of calibers:

Allen Xpress Wildcats

 

[Jeffvn]

If 3,100 fps is your goal w/ 338 LM boltface, there are lots of variants to consider. I use one version of the 338LM Improved, and its been an interesting evolution and learning experience over the last 3-4 years of shooting it. Case capacity is a key, and in my mind so is barrel length. My 32" is too long for anything beyond fixed point type hunting, but it works fine for shooting steel and busting rocks beyond 2,000 yards in the desert (so far I've had it to 2,100 yards, but 2,300 is our next stop when we go to the desert).

I currently shoot 300 gr. Scenars (and before that 300 gr. SMKs) @ 3,000 fps node with mine. I saw 3,100+ fps during load testing with RL-33 (108 gr., 109 gr.) It was not over pressure, but I was nervous about the 110+ degree summers here in Las Vegas, and elected to shoot the lower node (105.5 gr.). Similar results with VV570 (but finding that powder is as likely as seeing a unicorn). Retumbo and H1000 shot 2,900+ in my rifle.

Jeffvn

 

[jfields]

Thanks for all the great info, guys. I'll take all of this in to consideration when I get my barrel and send it to the smith.

 

[stenger]

Built one a few years back. It shoots best with 300gr Bergers at 2950.