I have tested this thoroughly with all GPS bombs. I have been able to get hits 100% of the time. My conclusion here is that you are either too slow ( below 500 indicated), too far out in the LAR ring releasing in the first 0-100 range, or a combination of the two. If you can try adjusting your methods as I have described here. I will leave this here until you can confirm that adjusting speed has rectified the issue.