BGC Bullet Comparator
Bob Green's custom shop is now offering one of the most interesting accuracy enhancing products to come along in some time, the Bob Green Custom Comparator. This new design came about as a result of customers seeking to understand why different lots of bullets would not shoot as well as others. What we found, especially regarding VLD bullets, was that the point on the bullet where the bullet seater makes contact and the point on the bullet where the lands make contact would vary from bullet-to-bullet and from lot-to-lot. With this device you are able to definitively sort bullets into sub-lots, therefore keeping the loaded rounds seating depth much more consistent without constantly chasing your bullet seating depth. The results on the target have been outstanding. Shooters have cut their group sizes in half and virtually eliminated flyers.
We offer this tool in 6mm, 6.5mm, 7mm and 308 calibers with or without .0001" indicators. One indicator will fit all comparators, eliminating the need for multiple indicators, keeping the comparator's cost effective.
Please read the review below by one of our customers, Dean Mihalovits.
"I shoot short and long range bench rest, and have been reasonably successful at both. Bob Green is my gunsmith and shooting mentor. Recently he developed a new reloading tool, on which I would like to give you a report. First some background. I acquired some of the first 6.5 x 47 Lapua brass to enter the country in 2007. I put a new Krieger barrel chambered for the 6.5 x 47 on a good tactical rifle I own. I also obtained 300 of the first lot of the new Berger 6.5mm 130 gr. VLD bullets. After working up a good load these bullets would consistently group in the high .3’s M.O.A. at 300 yards. When I ran out of that lot I bought 800 of the next lot that Berger made. I tried them in all of my better loads, but they would not group better than .75 M.O.A. I checked the first lot with a Sinclair bullet comparator “nut” (ogive to bullet base) and got the usual variance of = .003, which I typically got with any makers of unsorted V.L.D.’s. When I checked the second lot the variation was = .007. I asked Bob if this larger variation could be a possible cause of the larger groups. In response he asked, 'Why do you think variation in this dimension by itself would affect accuracy?' I said it was a good question, but that I really didn’t have an answer. I knew experience shooters sorted V.L.D.’s by weight to reduce vertical stringing at longer ranges. I had no experience with other types of sorting. Bob knew the right direction to take. He designed a custom bullet/loaded round comparator caliper tool. I loaded up 10 rounds and checked the cartridge overall length (OAL) with the caliper tool and found a length variation of .006!! Everyone knows that even a .003 change in cartridge OAL can dramatically change group size. After careful thought, we determined that variation in the dimension from the spot on the bullet nose where the seater stem makes contact, to the spot on the bullet that contacts the leade/lands of the barrel, would produce similar variation in the cartridge OAL The tool Bob developed, the BGC comparator, measures that dimension using a tenth (.0001”) indicator. I sorted 600 of the Berger 6.5mm V.L.D. bullets into six sub-lots. From smallest to largest bullet, the variation was .0030 to .0070. That’s a variation of .004. The four primary sub-lots were as follows: 1) .0041 to .0045: 80 pc 2) .0046 to .0050: 140 pc 3) .0051 to .0055: 210 pc 4) .0056 to .0060: 135 pc. I loaded 25 rounds with bullets from sub-lot #2 and my O.A.L. variation shrank to = .0015. At the range my group size shrank from .75 MOA to .38 MOA @ 300 yards. I feel this comparator / sorting tool really works!"
Dean Mihalovits.