I prefer to use the original powder slides, but I have found that you can't trust the markings, both because some powders have changed over the years, and because many of the original powder slides have been modified. I find that Bullseye powder slides always drop .2-.3 grains more than what's marked on the slide.
I have measured the hole size on all of my powder slides and calculated the volume of the hole. I then look up that volume on the Lee Auto Disk chart to see how much powder of any particular type that slide should drop. I comes out remarkably close.
http://www.leeprecision.com/cgi-data/instruct/AD2302.pdfStar powder slides tend to have tapered holes, so I measure the diameter at both the top and bottom of the hole and take the average.
Hole Diameter
00 Powder Slide Top Diameter Bottom Diameter Average Diameter Height Volume Cu In Volume CC
231 1.9 0.205 0.201 0.203 0.312 0.0101 0.165
BE 2.0 0.230 0.224 0.227 0.312 0.0126 0.207
BE 2.2 0.243 0.237 0.240 0.312 0.0141 0.231
BE 2.3 0.259 0.254 0.257 0.312 0.0161 0.264
BE 2.5 0.266 0.260 0.263 0.312 0.0169 0.278
231 3.1 0.273 0.259 0.266 0.312 0.0173 0.284
BE 2.7 0.275 0.270 0.273 0.312 0.0182 0.298
BE 2.7 0.274 0.267 0.271 0.312 0.0179 0.294
BE 2.8 0.279 0.273 0.276 0.312 0.0187 0.306
BE 2.9 0.284 0.278 0.281 0.312 0.0193 0.317
BE 3.0 0.290 0.285 0.288 0.312 0.0203 0.332
BE 3.2 0.303 0.294 0.299 0.312 0.0218 0.358
700x 2.6 0.305 0.298 0.302 0.312 0.0223 0.365
BE 3.3 0.306 0.302 0.304 0.312 0.0226 0.371
5066 3.1 0.310 0.310 0.310 0.312 0.0235 0.386
BE 3.5 0.317 0.311 0.314 0.312 0.0242 0.396
BE 3.6 0.320 0.314 0.317 0.312 0.0246 0.404
700X 3.2 0.322 0.316 0.319 0.312 0.0249 0.409
BE 3.7 0.323 0.316 0.320 0.312 0.0250 0.410
BE 3.8 (mod.) 0.342 0.343 0.343 0.312 0.0287 0.471
BE 4.0 0.331 0.325 0.328 0.312 0.0264 0.432
BE 4.2 0.332 0.337 0.335 0.312 0.0274 0.449
BE 4.4 0.345 0.339 0.342 0.312 0.0287 0.470
BE 4.5 0.346 0.342 0.344 0.312 0.0290 0.475
BE 4.6 0.352 0.347 0.350 0.312 0.0299 0.491
BE 4.7 0.355 0.349 0.352 0.312 0.0304 0.498
700X 3.9 0.362 0.356 0.359 0.312 0.0316 0.518
BE 5.0 0.365 0.359 0.362 0.312 0.0321 0.526
231 6.7 0.383 0.379 0.381 0.312 0.0356 0.583
BE 5.5 0.391 0.378 0.385 0.312 0.0362 0.594
Unique 7.0 0.429 0.421 0.425 0.312 0.0443 0.725