I'd love to know the burn temp of N565. I currently shoot N165 in my 6SLR and it works great on barrel life and accuracy.
Yes, a very interesting question that. Viht tends to use quite high nitroglycerin percentages in its N500 series powders which also tends to make them considerably slower burning than their N100 equivalents in real terms despite what Viht says in its literature. I suspect there will be a significant barrel life cost in the SLR substituting N565 for 165 in this relatively over-bore capacity combination. (Might just be fun though anyway!)
I've just bought a tin of 565 myself for a long-freebore 260 Rem as Viht has published some loads for it in both 260 and 6.5X55mm. I'll be able to compare it against N160, 560, and 165 eventually with 140s in it. So far, N560 is producing MVs over 100 fps below QuickLOAD predictions whereas N550 exceeded them and I pulled my three hottest loaded test cartridges.
Viht has 'pushed' N565 quite hard in Europe in its marketing for the 338 Lapua Magnum. Looking at the company's load data for this cartridge, there are few tables that incorporate 165, 560, 565, 170, and 570 to allow comparisons, but one is for the 250gn Berger OTM Tactical where maximum charges and MVs are as follows:
N165 ........... 89.5gn/2,851
N560 ........... 89.0gn/2,907
N565 ........... 92.1gn/2,920
N170 ........... 94.3gn/2,858
N570 ........... 96.9gn/2,959
That's a 2.4% MV increase for a 2.9% charge weight addition for N565 v 165, a lower ratio than N570 v 170 (4.9% more velocity for +2.75% charge) and only just improves on a 3.1gn lighter charge of N560.
That
suggests (on a sample data-set of one!) that N565 is a fair bit 'milder' than either N560 or N570.