I got a SSK 300 grain Mold in the early 80's before there was published data. I don't think hard cast 300 grain 44 mags go fast enough to require a gas check. Everybody thinks 2400 is the only powder for 44 mag, you might look at H-110/ WW 296. Depending on what gun you are using, you can load up a 300 that will destroy a S&W but be fine in a Ruger. Just because a load won't blow the gun up, don't assume your revolver won't shake apart after a 1000 or so rounds (many old time silhouette shooters couldn't get a season full out of a standard Model 29, so the 8 3/8" 29 Classic had a beefed up system to last a whole season before returning to the factory!)
I am a fan of heavy bullets at moderate speed! There is a learning curve for trajectory though! On paper a 30-06 will out do a 45-70 in almost every way, but in the real world big heavy bullets out perform when it counts. (Ask the American Bison!) You just need to able to get the distance right.
I have used quite a few hundred 300's in a T/C 14" with results that are astounding on any target but paper. The groups are fine, but you can do that with a 22 rim fire. Shoot a thing, just about ANY thing, with a 44-300 and you will be shocked! I once took a 5 gallon bucket filled with water and burped all the air from under the lid, and on top filled a second lidless bucket to the top. When I shot the lower bucket from about 35 yards, the water spout was 25 to 30 yards tall, and I did get wet (over 100 feet away!) I have shot free standing concrete blocks at 50 yards and had them vanish, with only a small amount of white powder and pea gravel left!
While you could make your bullets into hollow points with a 3/16" drill bit, it isn't necessary with medium hardness solids. The thumb sized entry, and shoe sized exit holes on wet soft targets or game, don't really require expansion aides!
Enjoy the big boom! Ivan