I don't think you are listening. At all.
If your solid case head has swelled .003, you are running sky high pressure. Sky high.
Same powder = same velocity = same pressure. Those are words to live by. Slightly faster lot, less of it to = same velocity, but still = same pressure. Slower lot, more of it to = same velocity, but still = same pressure. Not technically 100% precisely true, but as a general rule, it's a good one to live by.
Whatever FPS you are running with that load, you can't get there with the same powder without the same pressure. Can't get there from here.
Back off a helluva lot more than a grain. 10% would be more like it. Start working up while carefully measuring case head expansion. Personally, I don't like to see any case head expansion, period. But if I'm in a real hot rodding mood and I'm okay with short brass life, I'll tolerate .001 as long as it doesn't affect function. I wouldn't tolerate a load that causes .0015, for any reason. I'd run the fawk away from a load that causes .003. Hearing that it's a tight chamber, and still getting .003, I'd run fast and far from that load.
Just my take.
- DAA