Model 12's sometimes develop cracks.

I don't think anyone knows for sure why, and it likely varies from gun to gun.

So frame cracks on a model 12 or any airweight J frame are always a concern.

But my attitude is a gun is made for a purpose, and I'm not going to refrain from using it for that purpose.

If it cracks, then replace it. It's helped protect you for as long as you have had it, so its served it purpose.

So I would shoot enough +P gold dots to be sure you know the point of impact, and then practice with normal pressure range loads.