Like stick a bullet in your barrel but as long as they shoot consistently and they reach that muzzle velocity, they probably won't. 520 fps is very slow for a firearm projectile but it's fast enough. An arrow goes 350 fps. Paintballs go 300 fps. The slowest pellet guns do about the same.

You probably won't even get near to sticking a bullet in the barrel as long as your 1911 functions.

I'd have no problem with a .38 at about 600 fps. Using a powder that burns well under light loads, I'd drop the charge back until the pistol quits functioning (making darn sure that all the bullets hit the target solidly) then add a little more in to optimize what you want.

I had good luck using Acc#7 and a 147 grain bullet at very low levels in 9mm Luger which shot so well, I was sure that I could drop the charge more if I wanted. And the most accurate target load I've ever built.

So my story is to feel free to decrease loads AS LONG AS YOU AREN'T EVEN CLOSE to sticking a bullet in the barrel by checking the target EACH shot. And if it's not consistent, it's too much. I'm going to differ with conventional wisdom here. Jacketed bullets these days are bonded to the core and have enough jacket on the ogive to keep a bullet from shedding its jacket in the barrel. Here, though, you have to be very careful that you use bullets that aren't going to come apart and be very careful that somehow a jacket doesn't get left behind in your barrel. No old jacketed bullets and no 'half jacketed either. I'd use a dowel to check until you are sure you can depend on them. And stay with the same bullets.

Safety is primary. And if you push the bounds it needs to be more than primary.

PS. The light charges are not in danger of 'detonating'. Experts agree that kabooms caused by low powder charges are from firing a shot AFTER a bullet is stuck in the barrel. Not from the powder charge.

PPS. I would weigh each charge in this situation.

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