going to legthen the throat for 80 gr amax what legth to ogive?

been searching here and on other sites in an old post her i put that my mcgowen 8t 26 223 barrel was short throated and would not shoot 75-80 bullets out of it with out seating the heads DEEP in the case. well my gunsmith said he can legthen the throat for 20.00 i just need to give him a dumm cartridge to use . anyone has a cartridge depth they want to share for 80 gr amax bullets i know i can use the book coal just figured i would see what ya'll use and make one up . this rifle will be used for f t/r 300 yd and tactical out to 1000 yds so i want to shoot 80gr amax from it and might play with some 75's i have left over but 80 gr is the primary load.

..Just measure the neck lenght of the case..& mark the bullet from the bottom the same lenght & seat it to that in the neck...Less the boat tail of course...Start at the shoulder...

For gas guns, 2.500-2.550" OAL for a S80MK was a typical value last time I played with those. Usually that was long enough to get the bullet seated out far enough to not take up a huge amount of case capacity, while still allowing good accuracy with mag length loads for other stuff. For a bolt gun, you could probably stretch that out even further.

I've got a 24" LW 1-8 tw .223 Rem that shoots beautifully - but the throat is short enough that a B80VLD jammed 10 thou into the lands measures only 2.400" OAL...