42gr varget and 168smk = Great load
44gr varget and 175smk = unknown
Im a little confused as to the question. If you are asking whether 5 time shot .308 brass is safe with 44grains of varget and a SMK 175, then Maybe. Who's chamber is in each barrel? That will play a difference on case stretch in relation to overall pressure spike. Basically, the further the case has to expand to hit the chamber walls then the less felt pressure the bullet will be pushed along with. I would be very careful with any new load, especially since your taking that load between two guns. But, with that being said, as long as you don't see any stress fractures , primer cratering or other known pressure issues you will probably be fine.
Keep in mind, there is no Magic load that will work with two different barrels, actions etc...
Each gun is unique all the way down to the levels of stored energy in the barrels from the chambering process. You really should have a load developed for each rifle. Now load development is another topic and I have a couple of nice workups on the subject if your interested just let me know.
I shoot palma , which is Iron Sights at 1000 yards from a coat and sling in .308 and we use 28 " barrels shooting 155.5 grain Berger or SMK 155 with 45-46 grains of varget to get that 3000 fps mark you need to keep them supersonic at 1000. I reload my brass 10-15 times minimum. I also ALWAYS full length resize. It's good practice to create sets of brass which are all on the same number of reloads so when one decides to split a neck , you can toss the lot of them and start fresh.
REMEMBER , VELOCITY DOESN'T WIN MATCHES, ACCURACY DOES.