Case Life?

If you reload like I do and process in batches, then I'd suggest taking the number you want to shoot per week and triple it. So if you want to shoot 10 rounds a week, then 30 cases will do you. I always have a batch just back from the range in the tumbler. Another batch being sized and trimmed. And then another being loaded.

Of course you'll always be picking up brass, or looking for it on sale. As the brass approaches EOL then it will start to split out. If you tightly control your batches then the whole lot of 10 could split out in the same range session. If you are always introducing range pickups and not that picky about heritage, then culls will be a continuous 1 or 2 per range session.

Life per case is dependent upon numerous variables, but the main one is the stress of the load. Hot load = Short life.

"...wondering if the brass would last longer than..." Nope. It's the load that matters. With those two cartridges, buy as much as you can afford when you can. Neither is exactly easy to come by these days.
Midway wants $34.99 per 100 for brass Remington .222. $137.99 per 500. $28.99 per 100, $136.99 per 500 for Winchester.
$29.49 per 50, $246.99 per 500 for Winchester .300 Savage. $49.99 per 100 for Remington. Not sold by 500. 1,000 is $428.99(ouch).
Midway isn't the least expensive place though. Do a net search.

Within reason, it's not how hot you load but how well the brass fits your chamber. As to expense? Use .223 and .308 brass. Just resize in your dies and trim. Much cheaper and just as good.

I load 5.56X45MM to duplicate military M193 Ball, and I usually get 8-10 loads per case. Never loaded .300 Savage, but pressures are similar to original .30-06 factory loads, so 8-10 should be a reasonable expectation.

Is your .300 Savage a Model 99 lever-action?

If so, brass life will not be all that great as the 99 action allows a lot of case stretch. And the case must be FL sized every time for use in the lever-action.

Your case life will be determined with an L-bent paper clip and reaching down inside to feel for a stretch ring.

When you can feel it, the case is just about ready to suffer a case head seperation.

rc

Dang Walkalong!
I didn't know you were an Artest' too!

That is a real good drawing, and a great tool selection to go with it!!
I may have to steal it sometime!!

rc

I've never tried to neck down 5.56X45 ro .222 but since the .222 was the "parent" case that the 5.56 was designed from it shouldn't be a problem.

I wouldn't bother with annealing since 5.56 is so close to .222 and cheap and readily available, but I would check neck thickness closely after forming and trimming, and if necessary inside ream or outside turn (preferable, IMHO) to makle sure the case necks were "in spec."