This is one of those "Rifle Building Secrets" that are often found on custom built guns. When I refer to "lock plate polishing" I am referring to polishing the INSIDE of the lock plate. Here is what I do:
(1) I dis-assemble the lock and put all the parts in one of those plastic boxes with a lid. This keeps the parts from being lost.
(2) Then I use a small piece of flat steel as my "sanding block." I simply wrap a finer grade of Emery Paper (600 Grit) around it and start polishing the inside of the lock. I generally do this while sitting in the easy chair at home watching TV. The "trick" is not to get in a hurry.
(3) Then I use progressively finer grades of Emery Paper until the inside of the lock is polished "mirror bright." I also polish the arbor hole in the lock plate for the tumbler and the body of the Sear Screw. How "bright" do I get the back of the lock plate? When I can see my face in the polished back of the lock plate, I consider it done.
(4) Then I lightly oil the lock plate and set it aside.
(5) Then I carefully polish the other lock plate parts that either rub against each other in the "firing cycle" OR rub against the back of the lock plate.
(6) I will usually grind a bit off of the Sear Spring to weaken it just a tad. The Sear Spring directly affects your "Trigger Pull." I grind down the spring about 1/4th of its across the width of the arm that contacts the Sear.
When grinding down the Sear Spring I will hold it in my bare fingers. This is so I can feel it when it starts to get hot. When it does, I dip it in water. The idea is to keep from getting the Sear Spring so hot that it destroys the "temper" of the spring.
So what does all of this accomplish?
First and foremost, when the lock is re-assembled and lubricated, the "Trigger Pull" of the lock will generally be decreased to somewhere between 3 and 6 pounds of "Pull." The "ideal pull" and the N-SSA minimum is 3 pounds.
The BIG ADVANTAGE of this approach is that I do not have to mess with the stoning the sear nose and the "full cock" notch in the tumbler. These angles have to be kept precisely the same or the lock will have a tendency to catch in the "Half Cock" notch when the shooter attempts to fire the gun. Enfield locks are especially prone to this malady from a botched "Trigger Job."
Also keep in mind that "Case Hardening" is a thin"skin" of steel with a high carbon content that provides a hard, durable surface. When stoning the sear and sear notch it is awfully easy to break through that "skin" of hardened metal to the soft metal below. If you do, then your "trigger pull" will be constantly changing as the metal in the sear nose and tumbler notch deform and eventually making the gun unsafe to use.
Just to be on the "Safe Side" when I have to do some sear stoning, I always caseharden the lock parts just as a matter of general principal.
ANOTHER ADVANTAGE of a fully polished lock is "Decreased Lock Time." That is defined as the time from when the trigger trips the sear and the hammer begins its fall to the instant the gun fires. This reduced lock time is caused by the lessened friction in the lock because of the polished surfaces of the lock parts move easily and faster. Decreased lock times definitely enhance the accuracy of the rifle.
So, all in all there is a lot to be said for Lock Polishing, especially if you want enhance the "accuracy" of your rifle.
(1) I dis-assemble the lock and put all the parts in one of those plastic boxes with a lid. This keeps the parts from being lost.
(2) Then I use a small piece of flat steel as my "sanding block." I simply wrap a finer grade of Emery Paper (600 Grit) around it and start polishing the inside of the lock. I generally do this while sitting in the easy chair at home watching TV. The "trick" is not to get in a hurry.
(3) Then I use progressively finer grades of Emery Paper until the inside of the lock is polished "mirror bright." I also polish the arbor hole in the lock plate for the tumbler and the body of the Sear Screw. How "bright" do I get the back of the lock plate? When I can see my face in the polished back of the lock plate, I consider it done.
(4) Then I lightly oil the lock plate and set it aside.
(5) Then I carefully polish the other lock plate parts that either rub against each other in the "firing cycle" OR rub against the back of the lock plate.
(6) I will usually grind a bit off of the Sear Spring to weaken it just a tad. The Sear Spring directly affects your "Trigger Pull." I grind down the spring about 1/4th of its across the width of the arm that contacts the Sear.
When grinding down the Sear Spring I will hold it in my bare fingers. This is so I can feel it when it starts to get hot. When it does, I dip it in water. The idea is to keep from getting the Sear Spring so hot that it destroys the "temper" of the spring.
So what does all of this accomplish?
First and foremost, when the lock is re-assembled and lubricated, the "Trigger Pull" of the lock will generally be decreased to somewhere between 3 and 6 pounds of "Pull." The "ideal pull" and the N-SSA minimum is 3 pounds.
The BIG ADVANTAGE of this approach is that I do not have to mess with the stoning the sear nose and the "full cock" notch in the tumbler. These angles have to be kept precisely the same or the lock will have a tendency to catch in the "Half Cock" notch when the shooter attempts to fire the gun. Enfield locks are especially prone to this malady from a botched "Trigger Job."
Also keep in mind that "Case Hardening" is a thin"skin" of steel with a high carbon content that provides a hard, durable surface. When stoning the sear and sear notch it is awfully easy to break through that "skin" of hardened metal to the soft metal below. If you do, then your "trigger pull" will be constantly changing as the metal in the sear nose and tumbler notch deform and eventually making the gun unsafe to use.
Just to be on the "Safe Side" when I have to do some sear stoning, I always caseharden the lock parts just as a matter of general principal.
ANOTHER ADVANTAGE of a fully polished lock is "Decreased Lock Time." That is defined as the time from when the trigger trips the sear and the hammer begins its fall to the instant the gun fires. This reduced lock time is caused by the lessened friction in the lock because of the polished surfaces of the lock parts move easily and faster. Decreased lock times definitely enhance the accuracy of the rifle.
So, all in all there is a lot to be said for Lock Polishing, especially if you want enhance the "accuracy" of your rifle.