It's going to be pretty difficult to index the barrel correctly to drill for the front sight. Being off one way or the other will prevent the gun from shooting correctly. Before you go fooling with it, contact a good pistol smith to see what he charges to do the work. It might not be as much as you think and gunsmiths are able to ship the gun right back to your door. As flatgate mentioned, "do it yourself" gunsmithing can and often will have disasterous results without proper tools and kowledge. The muzzle needs to be perfectly cut at 90 degrees otherwise, the gas behind the bullet will escape quicker from one point, rather than escape around the entire bullet circumfrence instantly. If the later doesn't happen, the bullet will be canted sideways from the uneven discharge and the gun will NEVER shoot accurately unless the muzzle is recrowned.
Here is how I did it. It was a blued steel barrel, not stainless, but a barrel's a barrel.
I first measured the barrel and marked it at the length I wanted it to end up. I wrapped it with masking tape at that point. Then I used a hack saw to amputate the extra barrel. I left about 3/16" of barrel past the tape so I could bring it down square.
To finish the job I got a couple very sharp (new) fine files and a small carpenters square. Using the square as a guide I went around and around and around the barrel with the files until I was satisfied it was square with the bore. Not hard just time consuming.
To crown the muzzle I used a new rotary file in a hand drill. I held the rifle in one hand and eyeballed it then slowly put a small crown on it.
To seat the front sight I eyeballed that and epoxied it on.
I must have done something right because that little .22 shot very small groups. A neighbor bought it from me some time later and raved about it's accuracy.
Now I was only about 22 then and my eyes were a lot better than they are now. So I sure wouldn't try to eyeball a crown job today. I'd pay the bucks and buy a crowning tool from Brownells. Matter of fact they make a piloted facing cutter that will cut the barrel square to the bore for you.
That is what I'd do today.
As for the front sight, I got that all figured out.
Buy a roll of double sided tape and stick your front sight to the barrel with it. Eyeball it and adjust it till you are happy with it. Then with the sight still taped to the barrel get it set up in your drill press, ( I wouldn't do it by hand ) and start your hole. Then pull the sight off and finish it.
as Granddadd said, "measure twice, cut ONCE...."
yes, before you cut the barrel, whatever way YOU want to cut it and being its stainless, you should not have a lot of issues as to " fit & finish..." it will clean up quite nicely.....
mark the barrel where you want it to "end up " ( the length you desire)
,and when you remove ( unscrew the front sight) you will see how far back the hole is from the front ( the muzzle) so you mark a small line, this SAME distance right there, behind your 'mark'......now with a straight edge, you go from the "center" rear sight hole ( elevation screw hole..) and you center the straight edge to the "center' of the front sight hole, and you again, "Mark" where it crosses the line for the "set back " distance.....this will give you "top dead center..." of the existing holes , that are currently being used on the gun....ta daa......... 'now you can cut the barrel off, stay a bit ahead of your "finish" line, so you can properly true up ( sqaure) the end of the muzzle....there are barrel reamers(muzzle & crown, combination...), with a plug for a true "perfect" muzzlem but they are costly, Brownells has them , maybe Midway too, or Mittermier???but why spend extra money for something you may NEVER have a need for anymore.....we just use a jig (fixture) cut and file down to the face of the fixture and its done and square.........you can cut a crown ,by hand,nothing fancy, its NOT a " match competition target firearm....." :wink:
drill ( a number #31 drill bit) and tap the hole for the front sight using a 6x 48 tpi ( thats what we use for MOST gun stuff...) Ruger may use a 6 x40?? not sure, never bothered to measure one really........the other is MORE "common' for guns ......drill the hole, using a "depth" gage(stop). so you do NOT drill through...you can always have some machinist do this part of it for you,....every one has a "machinist" in their family ( or a neighbor??) don't they?? ( don;t take it to work and have the boys do it as a "government job" someone may get fired for bringing a gun to work...) 8)
anyway, not that hard or complicated,this is NOT "rocket science"........lots of guys, who are NOT "gunsmiths" have cut down and shortened barrels over time. some do a nice job, take their time, and others "jury rig, (Bubba) or do a "schwak" job....hacksaws & pipecutters.
OR you can hire a gunsmith ,pull the barrel and have it turned down in a 'lathe', and pay for all of these steps ( operations....)