Now believe it or not, sourcing a low profile 75 minute rail is probably going to be a lost cause. In fact I did not even bother to look for one. Instead this was machined in the mill.
First job was to calculate the cut in millimetres because, despite my age, that is what I always work in given the chance. I have a spreadsheet that I use and just enter the ring separation and the required angle in minutes and voilà, it comes up with a number. I wrote the years ago as it is so much easier than getting a pencil and paper out and doing it the long way, plus I can easily add or subtract the minutes required to see the difference to the depth of cut. Most I have ever machined for a rail was 125 minutes. Yes, It converts to milliradians as well because that is what I was brought up with. (Reminds me of a comp I shot one day at Bisley, as I stood up someone asked me how much wind I was putting on, ‘About 18 mils was my reply’)
Then out with sine gauge and try and get the rail clamped in the Bridgeport courtesy of the new machine vice. Finally check the end heights just in case and put a few cuts across the underside of the rail, remembering to take the material from the front and not the back!
So here it is, a BSA inter bracket and rail ready for 400 yards .22LR competitions.