"I'm wondering if I can push a hard cast with out gas checks to the 1300-1550 fps range without problems."
Simple answer, YES.
"Correct me if I'm wrong but doesn't a lead bullet require a gas check for these types of velocities to prevent heavy leading of the barrel?"
Simple answer, NO.
Not so simple answers.
The interior of a barrel 'leads' because of several factors. Pushing the bullet too fast or too tight of twist or too soft/malleable of bullet surface material and others.
I have found that bullet to barrel fit is the biggest problem. If the bullet bounces down the barrel, all is not well. Conversely, if the bullet is massively over sized, we've got problems. For soft bullet material (lead) about .002 over size seams to work well. Harder/jacketed bullets that may be too much.
The bullet should seal the barrel to gasses. The base/butt of the bullets will need to be pushed into the body of the bullet to cause 'it' to swell and seal the barrel (this is called obturate). If the barrel isn't sealed hot gasses will burn down the side of the bullets and leading will occur.
For lead bullets, the bullet alloy can take the 'hardness' from dead soft to very hard. Add to this the rate that the lead cools will affect the hardness also. Rapid cooling makes larger lead crystal structures and the effect is harder lead. Slow cooling and smaller crystals are formed. Don't worry, over time the size of the crystals will even out.
Now we come to the 'gas check'. One view is that it protects the butt of the bullet from hot gases. Another is it scrapes the lead off. I don't know. But I do know that they do work.
Summing up.
If an alloy is selected that produces a harder lead (to know, a tester is needed) and the bullets is cast to very close to the end desired diameter (working the lead breaks down the crystals with the effect of making the surface softer) and is lubed (this has it's own science) properly, a 'gas check' is not needed for the listed velocities and beyond.
Side note. Some say that a gas checked bullet with out the gas check looses accuracy. I personnel have never tested for this. But if this is correct, what about my bevel based bullets and all of those boat tailed bullets? It could be that the butt of the gas checked bullet with out the gas check isn't as flat/level/concentric?
I most likely only irritated some and I'm sure some of my views are incorrect and I will be told so. But, this is how I see it. I cast my first bullets in 1963 and they worked for me then. So I can be all wrong.
Enjoy, for that is what it is all about.
OSOK