[Nick_C_S]

I have no experience with 4756. But as I understand it, it's a medium-slow burning powder, best suited for larger, magnum-type calibers.

But if it's all you have, then it's all you have.

I think the key here is to not try to make it something it isn't. It is what it is. Okay I'm done with philosophy.

I don't know where your recipe needs to be, but we have thoroughly established that the current condition is very low pressure. In short, you definitely need more powder.

Have you performed a "plunk test" to determine the correct COL (or OAL, or COAL - whatever term you wish to use)? The first step is to set the COL for the bullet/gun combo.

Assuming it's set properly, your next step is to add powder. Given the condition of your brass and primer, you definitely need to add quite a bit more. Conservatively, 10% more (round up to the next 1/10th) would be next step. Although my gut tells me it won't be your last. (This is not to say that you'll be moving in 10% increments - this is just for the first time only. Additional steps will be much smaller.)

As I alluded before, by the time you've created a good clean burning, consistent round, you're going to have a full-power fire-breather. It'll be a good full power practice round - should be fun to shoot. That's what it's going to be - remember, don't try to make the loading something it can't be.