I won a TC Venture 300 Win Mag 2 weeks ago and plan on putting some loads together for it. It is the first of this caliber that I own so I had to scrounge up some brass and just got a decent pile in a trade that I made. A lot of the brass has dominion headstamps on it. I tried looking them up but have found nothing. All that I can figure is that they are OLD since dominion is long gone, and I guess they used hard brass. Looking at the moth of the case, the brass definitely seems thinner than any others. I gave them a quick tumble and found no cracks or defects at all on them.
I'm worried that they may be brittle from age, but I'm not the most experienced reloader anywhere so I may be wrong. Also, with the brass being thinner and harder, I'm assuming that they may not get uniform tension on the bullet?
I'm not expecting to punch round after round through the same hole but I need them to be consistent enough to hunt with and still be safe and reliable, so I'm not sure I'd they are worth messing with or not.
If anyone has any input or opinions on using this stuff i would appreciate it. It would be a shame to have to pitch all this brass in the trash.

I'd clean 'em up, load 'em up, and shoot 'em. That's the only way you're gonna find out,

Dominion brass is equal to American made brass - made by CIL when they were still manufacturing ammunition. Later cases will be headstamped Imperial. Am still using it for loads in a number of cartridges. Works well and has been durable.

Used to buy Dominion ammo for two cartridges back in the late 1960s. As mentioned Dominion was CIL, a Canadian company. CIL is Canadian Industries Limited, in Montreal. Remember I liked their Sabre point 30-06 ammo. While common today, the Sabre point was a blue nylon tip ammo I used in the late 60s. Don't know when it ceased business.

Did a little reloading back then and faintly recall it being decent brass, but didn't get many reloads out of the 30-06 brass. When I got back into guns/shooting/reloading about 7 years ago, still had some of the 30-06 CIL brass from my teenage years. I threw it away. However, I still have some of the Dominion 43 Mauser brass from the 60s that I had fireformed/trimmed back to use in a 43 Spanish Remington Argentine Rolling Block. Every once in awhile I shoot the rolling block using the Dominion brass with reduced Trail Boss loads to lob a 370 gr cast bullet downrange. Yep, I've had a couple of split necks with it this 50+ year old brass.

I'd hesitate to use Dominion in a 300 win mag.

I've used Imperial brass in my 7mag without any problems. I still have some of the stuff somewhere. I wouldn't hesitate to break it out and use it.