Be more than happy to give you the tips I know anyway. First off, that "TWANG" you feel when shooting, is the rebounding hammer bouncing back after firing. That made it so it will bounce back to the half cock position. That is an accuracy killer. While the bullet is traveling and leaving the barrel, the hammer is moving back at the same time. Can't be having things moving while the bullet is going down the barrel.
We will do these one at a time and maybe have to go back to it again, so read it all, and then you won't be taking it apart and back together over and over.
Now, all older Marlin 39A's as well as all other lever guns,have a true half cock position. These new 39A's with the rebounding safety do not. The old ones had a deep notch in the hammer that the trigger would slip into and be safe. The new ones only have a ledge in the hammer that the trigger rests ON, not IN. If done right, you can pull the hammer off the trigger. That's why I mentioned that once you do away with the rebounding hammer, you better use the crossbolt safety all the time.
Now to the easiest part, the rebounding hammer.
If you take the butt stock off, this will expose the rear tang area. You will see a spring that is over the hammer strut. The other end of the strut goes out like a "Y". There is an upper leg that seats in the back of the hammer. There is the lower leg ( of the "Y" ) that is the part that causes the hammer to rebound/bounce back. There is a metal piece that the hammer strut goes through. That metal piece sets in a slot in the tang. Just use a small hammer and knock this out to one side. You should now have the hammer strut and spring in your hand. LOOK>>>>> Before removing the strut, remember which leg is the lower one. Maybe put a piece of tape on it. All you need to do is cut off the lower leg where it meets at the "Y" . No need to cut it flat against it. Just as long as its gone. After re-installing the strut and spring. Your hammer should be down against the bolt all the time. You can still bring the hammer to the half cock position, but remember, its
just on a ledge. That's why you must use the safety.
While you have yours apart, look at how the trigger seats in the hammer in its different positions so you will know where the ledge is at the so called half cock and everything. That way you know what I mean. You will also see where your trigger sets when its ready to fire. The ledge, if too long, can be stoned down to make a better trigger pull. First things first.
Now, there are two ways to do this and the second I have not tried yet, but makes sense.
Because the hammer no longer bounces back, it hits the rim of the shell with too much force and causes a burr on the rim every time you shoot. This will cause the case to get stuck in the chamber. What I did, was very carefully shorten my firing pin with a needle file at the rear of the firing pin. To test this I pulled the bullets on about 10 rounds and dumped the powder. This gave me dummy rounds that went "POP" and no projectile. This lets you keep an eye on how the firing pin is doing. Once you get it to where it makes a good dent, but does not bend the rim out too far, you will be good to go.
Now to the trigger pull. Yes they are heavy. You can buy lighter weight hammer springs and this will even make the action work smoother. This may also help the hammer to not hit the firing pin so hard. You might want to get a spring before you do anything to the firing pin. You may not need to do a thing is the lighter spring hits lighter, which it should. I just don't know how much of a difference it will make. You may not have to touch the firing pin at all. That would be a good thing.
The hammer and trigger engagement.
This is where the hammer sets on the trigger at full cock. If you feel creep you might want to stone the front of the hammer where the notch is. This will shorten the distance you have to pull the trigger before the hammer falls. This should also be better to do after you get a lighter spring. The felt creep will be different with less tension on the trigger from the hammer. Meaning you will feel more creep. While stoning, or filing if that's all you have, you will cause burrs to raise up on the sharp edge. Make one pass with a needle file on the bottom of the notch on the hammer to knock off the burrs. Just work it a little at a time to get rid of the creep you do not want. To test that you have not removed too much, pull the hammer back all the way and let it fly. If it stops on the trigger every time. Your good to go.
That's about the gist of it. I know I didn't explain about removal of the hammer and trigger, but you will see its a simple task, but you can only do this with the hammer strut and spring out.
If I have confused you in any way, or you have any questions, don't hesitate to ask.
Hope this sheds some light on things.
Holler if you need anything at all,
Steve/ Gizzy @RFC
Also.... anyone with a brand new 39A,or if you start experiencing failure to fires, I have a fix for that also. I just shot a new 39A and had this problem. Seems that the hammer spring is extremely weak. I added three small washers on with the hammer spring, and this fixed it. Just be sure the washers are not any larger than the keeper than holds the hammer strut in. Your butt stock needs to slide right past that, and if you get washers that are too large, you won;t be able to get the butt stock back on. Total thickness of add on in case you would rather do a spacer is about 3/16".
We will do these one at a time and maybe have to go back to it again, so read it all, and then you won't be taking it apart and back together over and over.
Now, all older Marlin 39A's as well as all other lever guns,have a true half cock position. These new 39A's with the rebounding safety do not. The old ones had a deep notch in the hammer that the trigger would slip into and be safe. The new ones only have a ledge in the hammer that the trigger rests ON, not IN. If done right, you can pull the hammer off the trigger. That's why I mentioned that once you do away with the rebounding hammer, you better use the crossbolt safety all the time.
Now to the easiest part, the rebounding hammer.
If you take the butt stock off, this will expose the rear tang area. You will see a spring that is over the hammer strut. The other end of the strut goes out like a "Y". There is an upper leg that seats in the back of the hammer. There is the lower leg ( of the "Y" ) that is the part that causes the hammer to rebound/bounce back. There is a metal piece that the hammer strut goes through. That metal piece sets in a slot in the tang. Just use a small hammer and knock this out to one side. You should now have the hammer strut and spring in your hand. LOOK>>>>> Before removing the strut, remember which leg is the lower one. Maybe put a piece of tape on it. All you need to do is cut off the lower leg where it meets at the "Y" . No need to cut it flat against it. Just as long as its gone. After re-installing the strut and spring. Your hammer should be down against the bolt all the time. You can still bring the hammer to the half cock position, but remember, its
just on a ledge. That's why you must use the safety.
While you have yours apart, look at how the trigger seats in the hammer in its different positions so you will know where the ledge is at the so called half cock and everything. That way you know what I mean. You will also see where your trigger sets when its ready to fire. The ledge, if too long, can be stoned down to make a better trigger pull. First things first.
Now, there are two ways to do this and the second I have not tried yet, but makes sense.
Because the hammer no longer bounces back, it hits the rim of the shell with too much force and causes a burr on the rim every time you shoot. This will cause the case to get stuck in the chamber. What I did, was very carefully shorten my firing pin with a needle file at the rear of the firing pin. To test this I pulled the bullets on about 10 rounds and dumped the powder. This gave me dummy rounds that went "POP" and no projectile. This lets you keep an eye on how the firing pin is doing. Once you get it to where it makes a good dent, but does not bend the rim out too far, you will be good to go.
Now to the trigger pull. Yes they are heavy. You can buy lighter weight hammer springs and this will even make the action work smoother. This may also help the hammer to not hit the firing pin so hard. You might want to get a spring before you do anything to the firing pin. You may not need to do a thing is the lighter spring hits lighter, which it should. I just don't know how much of a difference it will make. You may not have to touch the firing pin at all. That would be a good thing.
The hammer and trigger engagement.
This is where the hammer sets on the trigger at full cock. If you feel creep you might want to stone the front of the hammer where the notch is. This will shorten the distance you have to pull the trigger before the hammer falls. This should also be better to do after you get a lighter spring. The felt creep will be different with less tension on the trigger from the hammer. Meaning you will feel more creep. While stoning, or filing if that's all you have, you will cause burrs to raise up on the sharp edge. Make one pass with a needle file on the bottom of the notch on the hammer to knock off the burrs. Just work it a little at a time to get rid of the creep you do not want. To test that you have not removed too much, pull the hammer back all the way and let it fly. If it stops on the trigger every time. Your good to go.
That's about the gist of it. I know I didn't explain about removal of the hammer and trigger, but you will see its a simple task, but you can only do this with the hammer strut and spring out.
If I have confused you in any way, or you have any questions, don't hesitate to ask.
Hope this sheds some light on things.
Holler if you need anything at all,
Steve/ Gizzy @RFC
Also.... anyone with a brand new 39A,or if you start experiencing failure to fires, I have a fix for that also. I just shot a new 39A and had this problem. Seems that the hammer spring is extremely weak. I added three small washers on with the hammer spring, and this fixed it. Just be sure the washers are not any larger than the keeper than holds the hammer strut in. Your butt stock needs to slide right past that, and if you get washers that are too large, you won;t be able to get the butt stock back on. Total thickness of add on in case you would rather do a spacer is about 3/16".