Starting in 1964 I spent two years behind the gun counter in a store that could buy Schultz and Larsen rifles and all Norma products, directly from the distributor, thus by-passing all wholesalers. The result was a lot of these rifles and Norma products were sold. The S&L rifles were nearly all in either 7x61 or 308 N mag. And the Norma ammo for them was loaded HOT. One fellow bought a 308 NM, took it home and after firing one shot, the bolt was locked solid! He brought it back to the shop that way, I took it to the back room and with a spruce 2x4 a foot and a half long, I whacked the bolt. Hard. After the third whack, it came open. The owner had done nothing wrong, except he didn't clean and polish the chamber! The rifle was fine after, and with a clean, dry chamber. The 7x61 rifles had to be treated the same. Only they did have a problem, and even the company wasn't sure what to do, except they lowered the pressure on Norma ammo and on Norma loading charts. The new ammo had a different head stamp.
At that time scopes were just getting popular and many hunters wanted their scoped rifles to be sighted in when they bought them. Thus, I did a lot of sighting in rifles, of all makes and as I have said before, the most accurate rifles I sighted in were the Schultz and Larsen in 7x61 and 308 N. Mag. I felt so good about them that I once took a 308 S&L in 308 N. Mag, to a country turkey shoot. The only problem was it turned out the shooting was from off hand, so I could have made a better choice on a rifle to take!
And their best accuracy always came from full blown loads. Norma 205 had just came on the market and we loaded right up to their specs with it and the pressure seemed to be the same as the hot Norma factory loads.
I think, without doubt, that best powder for them is in the range of Norma 205, or the original, war surplus, H4831.
Bruce