Here in Mexico we do not have expert gunsmiths to open a choke, so I do all my work in this arena.
You need: 1)A good quality variable reamer (actually you need 2 to open a 12 ga from full to skeet because diameters) and a handle, 2)a digital caliper, 3)a telescopic gauge (last 2 items to take mesures from the choke you are working), 4) some pork lard (I think other lubricants also work, but I use that because an advise from an old machinist) and 5) some fine sandpaper (600 girt).
Procedure:
1) Adjust the reamer to cut 0.001-0.002" (never more than 0.002")
2) Apply a little pork lard in the blades of the reamer
3) slowly cut the choke by hand motion (the reamer autocenter so you do not cut uneven as many people say)
4) Clean steel particles cutted from the reamer.
5) Repeat until the desired choke is obtained.
6) With the sandpaper polish a little (or as much as you desire) to abtain a nice finish (normally the cut from the reamer is nice, so you do not need to sand a lot.
I opened some chokes, both single barrel and doubles, by this procedure with always very good results.
Best,
Last edited by Jose Fernandez; 05/17/10 07:24 PM.
