Okay re-crowning is a nasty word if you own a rifle that needs it. This is a set back crown or counter bore.
This will be the easiest way to fix a damaged crown on your rifle and not have to reset your front sight ramp.
Say you have a 30-30 that needs it. Groove diameter is .308 to clean up a bad spot you need a drill that will completely cut the old groove. Most common size would be 5/16 or .312 this only removes .002 per side not much.
Scary, actually not that bad. A drill will follow a hollow even and square. Even if you are using a hand drill.
So you have decided to give it a try and here you are. I would start by estimating the amount of damage in barrel depth, say 1/2 inch. Okay wrap a piece of tape around the drill 1/2 inch from the end. When you've got it in that far stop and your done.
.35 Rem is .358 groove you would use the most common drill near it .375 or 3/8 about .009 per side.
Or buy a specialty drill bit that is at least .005 larger.
.44 or .444 groove is .429 7/16 is .437
.45 LC is .452 and 45-70 is .458 using the larger number for both 15/32 or .468
Again specialty drill such as letter drills or metric sizes can many times get you close to the .005 needed to just clean up your damaged crown, without removing the sight ramp and setting it back or bobbing the bbl.
But then a lot of folks still want a shorter gun and this will also make a nice crown when bobbing a bbl back by recessing it in the bbl which makes it square and even if the bbl is cut out of square by a little.
Hope this helps all you home do it your self folks. PS I have done this a few times and currently have one Marlin with a recessed crown and it shoots less than a minute at 100yds.
This will be the easiest way to fix a damaged crown on your rifle and not have to reset your front sight ramp.
Say you have a 30-30 that needs it. Groove diameter is .308 to clean up a bad spot you need a drill that will completely cut the old groove. Most common size would be 5/16 or .312 this only removes .002 per side not much.
Scary, actually not that bad. A drill will follow a hollow even and square. Even if you are using a hand drill.
So you have decided to give it a try and here you are. I would start by estimating the amount of damage in barrel depth, say 1/2 inch. Okay wrap a piece of tape around the drill 1/2 inch from the end. When you've got it in that far stop and your done.
.35 Rem is .358 groove you would use the most common drill near it .375 or 3/8 about .009 per side.
Or buy a specialty drill bit that is at least .005 larger.
.44 or .444 groove is .429 7/16 is .437
.45 LC is .452 and 45-70 is .458 using the larger number for both 15/32 or .468
Again specialty drill such as letter drills or metric sizes can many times get you close to the .005 needed to just clean up your damaged crown, without removing the sight ramp and setting it back or bobbing the bbl.
But then a lot of folks still want a shorter gun and this will also make a nice crown when bobbing a bbl back by recessing it in the bbl which makes it square and even if the bbl is cut out of square by a little.
Hope this helps all you home do it your self folks. PS I have done this a few times and currently have one Marlin with a recessed crown and it shoots less than a minute at 100yds.