My 141 power factor .38 Super loads drop them without hesitation, and even a .45 auto 185 SWC with a measly 5.0 gains of W231 would do the same thing, so my guess is you're either hitting too low or they aren't calibrated correctly.
The heavier bullet would be a good option if there's no chance of addressing the calibration issue and you're hitting them solidly.
As mentioned, Popper calibration and where you hit make a lot of difference, but neither should slow you down. Get the hit and keep going; don't wait to see the popper fall before going to the next target.
Try using 230 bullets using a fast powder calibrated for the powerfactor of the steel you are shooting. My favorite "old" 175PF load for ipsc was 230lrn with 4.0 Clays, dropping down to around 3.8 now. With the larger diameter round you need to use the bigger bullets with faster powder for less "FELT or PERCEIVED" recoil impulse. Whereas with the smaller diameter bullets (ie. 9mm, 38super) you can shoot faster velocity with smaller bullets and faster recovery time. Your thought to go to 200gr bullets was correct. Give it a go. Remember you want your load to take the steel down with a partial hit, just in case! Have a good one! Do you shoot at West Liberty or down at the USPSA matches down at Lowell? DC