Well I've got a 358 Win BLR with the pistol grip and it IS the best thing since sliced bread.
An excellent hunting caliber. Plus I've made about 400 rounds of brass by firing 308 factory ammo in the 358 Win chamber of my BLR !! The case dimensions of the 308 and the 358 are the same until well down the shoulder. The datum line is 0.420 at a length of of 1.606 inches for both cartridges. So the headspace is identical. Only try this with factory ammo or ammo that has been checked for headspace. Most of what I've done this with is Lake City MATCH. The accuracy isn't too good but most shots hit a 2 foot diameter rock about 200 yards away. My Oehler 35P Chronograph clocks the 150 grain 308 bullets at 1,250 fps when fired in the 358W BLR chamber. The brass fire-forms perfectly. Even looks a bit better than resized empties.
Once the new 338 Federal ammo hits the street, I'll do the same assuming the diameter and length of the datum line is identical. Always loved Federal Brass. I do have 20 Nickel Plated Federals that I fire-formed from 308. They do required about a 2.0 grain cut in the powder charge over the Winchester factory 385W cases, but they are very strong and feed just noticeably better than the plain brass.
Lee Pacesetter dies will form brass in a single pass from empty 308 cases. I use Hornady Unique lube, looks a lot like Crisco. In a safe area well away from any powder or primers I put a little rub around the case body. Then I warm the neck slightly with a lighter and dip the neck into the lube which coats the neck well inside and out with liquid lube leaving a cookie cutter surface on the lube. My Lee Cast Iron press handles that with an almost normal sizing stroke. If you haven't looked at the new Lee Cast Iron Press, check it out, this is a major leap in quality and features. I was amazed and the price was only $56 brand new.
Loads all in Winchester Componets unprimed 358Win Brass, with Winchester Large Rifle Magnum Primers
0.357 125 grain copper plated TMJ revolver bullet over 43.0 grains H380. I have yet to chronograph this load. But I'd make a rough extrapolation of about 2,900 fps. Note that is the low endpoint of the estimate, the middle would be 3,000 and the high estimate is 3,100 fps. This bullet has a BC of 0.122 but it is still awesome for practice, or pest control. Then muzzle energy at 2,900 fps is 2,343 ft-lbs which is just shy of P.O.Ackley's preferred Energy of 2,500 ft-lbs for Elk and Bear up to 600 pounds; a good bit more than his Adequate Energy of 2,000 ft-lbs for the same; and over his Minimum Energy of 2,100 ft-lbs for Moose and Large Bear. Remember that this is our plinking/pest control load. When zeroed at 150 yards this bullet is 0.6 inches high at 50 yards, 1.2 inches high at 100 yards and 3.8 inches low at 200 yards. The energies are 1,762 ft-lbs at 50 yards, 1,306 at 100 yards, 957 ft-lbs at 150 yards and 694 ft-lbs at 200 yards. So our varmint load stays over the 900 ft-lb Minimum Energy for Deer, Antelope, and Mountain Goats out to 150 yards. While it was pretty much expected that the velocities and especially the energies fall rapidly due to the low Ballistic coefficient. What was really surprising was the flat trajectory. Pretty much a flat string out to 175 yards.
Was going to give several loads such as 48 gr. AA2520, 250 gr. Nosler Partition with a BC of 0.446 gives a velociity of 2,400 fps. and 43.0 gr AA2520 with a Woodleigh 310 grain and a BC of 0.400 at 2,100 fps.
Enjoy your 358 Win BLR, I know I love mine.