Dumb question on velocity vs resistance

I've been loading up for my Uberti 73 Win a mess of 44-40's based on information I gathered on this site.
I'm using Extreme hard cast lead Bullets, 200g rnf sized to .430", over 24.7g of IMR4198.....starline brass, win large pistol primers.
I tried a few loads with 25.5g and they were accurate but I didn't want to get that close to the max load with 1512 f/s. (200g rnf sized to .429" Oregon Lazer cast) Info from 44 wcf I believe.
Now, last night I came across some old threads where one fellow (didn't note his hame or handle) who was only achieving 1300 with 25g but I didn't see what dia. bullet he was using.
And to add to my confusion, there's a video on Utube where a fellow was using H4198 and achieving over 1500 f/s with 25.5g of that powder. Which I understand burns even slower than the IMR4198.
I was thinking (not normally a smart thing for me to do) that I'd get around the high 13's or low 1400+ f/s with my loads using the tighter fitting projectile.
So my question is: using a .430", will that increase the pressures significantly and velocity? Or Not?

As a general rule you want your cast bullets to be around .001" over the groove diameter of your firearm. This goes for both pistols and rifles. If your cast bullets are at (or slightly under) groove diameter hot, high pressure gas can leak past the bullet and vaporize lead off of it's surface. When this vaporized lead cools it will condense and plate on the inside of the barrel. When a layer of lead film gets thick enough it will start galling and smearing lead off of every passing bullet, and this will cause barrel leading. With the bullet .001" or so over the groove size the bullets will seal the bore and prevent this barrel leading from happening.

Store bought cast bullets are made from harder alloys to prevent dents and damage during shipping. They're also sized to be "one size fits all", instead of being optimized for your specific firearm. I can't help you with your load development as I don't load that caliber, and the Lyman manuals that I just looked at don't list IMR-4198. So long as you stay away from maximum loads the difference in barrel friction and pressure between normal cast alloys and hard cast alloys will be marginal to the point of not being a concern. More important is selecting an alloy, and sizing the bullet, so that you get a good gas seal to prevent leading and get the best accuracy.

P.S. "There are no dumb questions - just dumb people"; one of my professors from college.

Thanks for your reply.......helps immensly.

I think what 405Grain is saying is..alloy in and of itself probably won't have an effect, on Velocity at all..assuming boolit Fit is the Same..But, going down your "road" something with Much More resistance...ie. Jacketed, will "matter".

"So my question is: using a .430", will that increase the pressures significantly and velocity? Or Not?"

No, with cast bullets the .001 increase in bullet will not significantly increase either if at all. However, in the smaller pistol cartridges the difference in seating depth [not to be confused with OAL] between two different bullets of the same weight can have an effect on pressure and velocity.