Fozzy,
I have built rifles in the 338 Lapua, 338 Kahn and my 338 AX and only use 1-10 twist barrels. In those rifles I have shot the 265 gr ULD RBBT and 350 gr ULD RBBT and in every case, I got excellent accuracy out to 1000 yards and beyond. With the 350 gr ULD RBBT, I was only getting around 2650 fps in the Lapua and around 2800 in the Kahn and AX.
I tell you this for one reason, the 265 gr AT RBBT and 350 gr ULD RBBT are DRAMATICALLY longer then the 300 gr SMK. If a 1-10 twist will produce excellent accuracy at 1000 yards and beyond with this extremely long bullet, the 300 gr SMK will most definately be completely stabilized in a 1-10 twist when fired to the 2800 to 2900 fps that the Edge can produce depending on barrel length.
The comments that were made about "Those Claiming" good results with a 1-10 are humerous. Sierra made the bullet, they have tested this bullet on more chamberings then anyone out there and from velocities that are VERY low to very high. They recommend a 1-10. I would listen to the experts concerning bullets and namely those that actually made and tested the bullets.
I have also found that in my 338 Allen Xpress, Retumbo was a far more consistant powder for bullets from 265 gr up to the 300 gr SMK. I tested H-1000, Rl-25, Retumbo, H-50BMG and US869.
For 250 gr bullets, H-1000 was about as good as you can get. For the 300 gr bullets, H-1000 worked very well but Retumbo offered higher velocity levels with less pressure signs which I expected would be the case as its a better choice. H-1000 is THE powder of choice for the 338 EDGE, ask Shawn Carlock, its designer. Retumbo also works well and in some rifles will get you a bit more velocity with similiar consistancy.
In my opinion, from my actual testing, US869 is not even in the top three powders for my 338 Allen Xpress which is an improved version of the 338 Lapua. ITs to slow in burn rate. It will certainly keep you out of any pressure problems as you simply can not get the pressure up to where it should be for a good clean burn with this powder which resulted in excessive carbon fouling compared to Retumbo.
Also, top velocity was not that impressive. I got around 2875 fps with US869 with the 300 gr SMK. Retumbo got me just shy of 2950 fps in a 27" barrel. 30" will get you just shy of 3000 fps in many cases with Retumbo.
Both loads were very accurate with decent extreme spreads for US869 but much tighter for Retumbo.
Also when tested in cold temps(20 degrees) compared to moderate temps(75 degrees), velocity spreads were much wider for US869 compared to retumbo. In fact average velocity with 869 increased an average of 78 fps with this temp change compared to 14 fps for Retumbo.
US869 is advertised as being very stable over wide temp ranges. It may be in the 50 BMG but it certainly is not in smaller bore sizes, at least in nothing I have tested it in.
It is much more appropriate in my 300 AX which is also on an improved version of the Lapua case but that is because the expansion ratio is much lower then with the 338 version.
Why do I bring all this up. My 338 AX has a decent case capacity advantage over the 338 Edge. If US869 is to slow for the AX it will be even worse in the Edge.
Again, no need to reinvent the wheel, use H-1000 or Retumbo in the Edge and go with a top quality 1-10 twist barrel. You will never have any problems at all. No need to change things just for the sake of saying you changed them. Use what has been proven to work hundreds of thousands of times before.
Just my opinion.
You will certainly not get into any serious problems with a faster twist. The Edge can not get into the velocity ranges that would result from accuracy issues from over spinning the 300 gr SMK. Hell I drive them to over 3400 fps in my 338 AM with amazing accuracy and in that case, 1-10 is much more then needed but it still works extremely well.
Kirby Allen(50)
