I run a light load ~45 grains of RL19 behind a Hornady 117 Interlock (cheap) that is seated tightly into the lands and against the bolt face (slight pressure when closing the bolt on a loaded round).
Step 1) For fire-forming brass prep, I recommend using Nosler .270 Win brass, and necking them down to .257 using the FL sizing die for your .25-06 AI. Setup your dies just like any other die, with slight cam-over at the top. I also recommend using Imperial Sizing Wax for sizing your brass. Don't use too much, just a very thin "film-like" layer. Be sure to wipe excess off each brass after sizing.
Step 2) After necking down your brass to .25 caliber, you will need to trim the brass to 2.514". This is because when the brass forms to your chamber the necks will shrink about .020", and if you leave them long, the brass (after forming) will be right at the perfect OAL of 2.494". After trimming, be sure to chamfer and deburr your case mouths.
Step 3) Using a Hornady 117 Interlock and a Hornady COAL gauge (standard Hornady 25-06 case gauge) and a comparator, measure your distance pressed into the lands. Be sure and write down this measurement. It will be important for Step 4. Also, every bullet brand, model, & weight you use is different, therefore will produce a different measurement, so you will need to re-measure this distance with each different bullet you plan to use in the future.
Step 4) Prime your brass, charge with a starting load for standard 25-06 using a 117 Interlock (Hornady 9th says around 45-46 grains), and then seat your bullets to whatever depth you determined in Step 3.
Step 5) The fun part. Go out and shoot 5 shots, let the barrel cool. Repeat till you get about 50 pieces of formed brass.
Step 6) After recapping and cleaning your newly formed cases, use your calipers to ensure they are forming between 2.490 to 2.494". If they are, all is well, and you can begin load workup using whatever bullets you prefer. I like Berger 115 VLD's in mine.
*** If you need any length to any of these specific tools that you might not already have, feel free to PM me, and I will send you links to them.
