Paper patch reduces dwell time but tends to align and fill the throat with less bullet alteration from the case to the barrel . The general consensus is that paper patch is slicker and moves easier and faster that lead and copper . Stepping down to a 6.5 bullet for 270 isn't too bad for weight options but others are difficult sometimes without custom moulds and sizers . 270 to 7mm because of the dearth of 270 moulds and 30 cal because there's not a 29 cal ......the Russians and Britt's however are readily available as there are 800 choices in 308-310 to shoot in the 310-316 grooves . I've been background dabbling with a 25 cal patch and even a 105 gr bullet is rare in 243 .
As a personal note the fat 6.5 , 270-140 NOE I think , won't go with a double wrap in a tight low mileage 270 × 784 barrel . The bare nose is too loose possibly with a coat of BLL it would be fine but then you have the potential of the patch sticking to the bullet . The really fat 31s can patch up to tight 32s .
Nothing really for 33/34 & 35 cal either , the 9.3 of course has a hoard of 35 cal bullets that will work . 375 ...... 9.3 moulds but not in my research windows for size and weight . 40s you're looking at old school and probably there are a number of BP moulds available in .401-.403 for the .408-410 rifles . 44s again not much past undersized pistol bullets for fat rifles . 45s are like a party but the Sharps etc that won't die and Quigley resurrection of the 45-70,90,100,110,120 probably has a lot to do with that .
22&24 are all on you for sizers .
My 1¢ on revs . It's a thing , you can work around it , the side effect of centrifugal force is just a killer on cast and if pushed far enough in a 30 will do it too . I do have a 1-8.5 06' that was probably a 1 off special order for super heavyweights when 250s were still available on the shelf . At 2750 dime 5 shot groups at 2690 are sideways and moving on up the results get worse . In the 1-12 308 2800 is still under a dollar for 10 shots , same profile , length , dia , very close throats ... It is in 308 and that rifle regardless of propaganda will not shoot a bullet over 175 gr , not even a 180 RN that's shorter than the 150 . Yeah yeah every rifle it's own rules ....... The only to absolutely prove or deny the rev thing would be to use a single rifling tool on a series of holes in a solid block of steel all cut with one drill and reamer set at different twists from 14-8 in 30 Cal . Even then on 1000 rounds per hole on single lot GI ammo all we'd have is a mountain of data and video it would take years to sort out and come to a conclusion .
Want something newish to fuss about ?
What happens to a cast bullet related to air density , in the first 20 ft out of the muzzle ? If the bullet is superSonic upon exit then the air mass immediately in front of it has to be either highly compressed or traveling supersonic also . I've seen an aircraft break up in a wind shear so what happens when the bullet exits the supersonic pushed air plume and hits the "clean" air ?
