grip safety?
If so, make SURE you are not depressing it when you put the slide back on the frame!!!
There is no grip safety on 39s.
My agency was the first in the US to issue autos and the 9mm. We carried the 39 and 39-2 for over 13 yrs before going to the 2nd generation S&W.
You can safely shoot +P ammo in the 39 but it will cause a bit more wear. How much more? You will probably never notice it unless you are shooting thousands and thousands of rds. Any of the quality brand defensive ammo will be suitable for your 39. No one is really making bad defensive ammo. Try several weights and carry what shoots best in your gun.
As Croyance wrote, the 39-2 had a different feed ramp than the 39 which was suppose to aid in feeding most types of HP ammo. The original 39 had a slight hump in the feed ramp which was to aid feeding of the FMJ ammo at the time. With the shorter HP ammo the hump would sometimes cause some feeding problems. Many LE 39 had the hump removed and the 39-2 was designed without the hump.
Clean after shooting it. It's not a big job.
Try a search on HR, the Firing Line, and Glocktalk for how to field strip S&W autos. I've posted it before for S&W autos. If you can't find it, here it is:
1) Remove the magazine.
2) Check the chamber. Make sure it's is empty.
3) Check the chamber. Make sure there is no ammo in the gun.
4) Check the chamber. Make sure the chamber is empty.
5) Did I mention to make sure the gun was unloaded?
6) Collect all the ammo. Place all the ammo in a ziplock bag. Take the bag with all the ammo in another room. Place the bag in a drawer. As you leave that room close the door. Do not return to that room until you are finished.
7) Return to the room where there is no ammo and which is now unloaded gun. Check the gun again to be sure it is unloaded.
8) Place the safety/decock lever in the 'fire' position (it should be pointing same direction as the barrel).
9) Notice where the slide lock/release lever is located on the left side. In front of the lever is a notch in the slide.
10) Pull the slide to the rear to where the notch in the slide is lined up with the front of the slide lock/release.
11) With the notch lined up with the front of the slide lock/release lever, from the right side push in the slide lock/release lever (small 'button' above the trigger).
12) This should move the slide lock/release lever out to where you can remove it rest of the way from the left.
13) Once the slide lock/release lever is removed the slide can be slide off to the front of the gun.
14) If the hammer is cocked, while removing the slide hold the hammer so it does not slam forward. After the slide is cleared let the hammer go forward to the at rest position. Do not dry fire the gun with the slide removed. The hammer banging on the frame can crack the frame at the point of contact.
15) When removing the slide, cup your hand around the slide so the spring/guide rod doesn't fly off. It's under some tension.
16) Lift the spring/guide rod out from the rear where it should be engaged in a small slot in the rear of the barrel.
17) Rotate the barrel bushing about 1/4 turn and remove it from the slide.
17) Lift the barrel out of the slide. You may have to giggle it a bit but it should come out easily.
That should be all you need to field strip the S&W autos. While the slide is off, DO NOT dry fire the gun. Doing so permits the hammer to strike the rear of the frame, eventually breaking the frame. I've seen a number of S&W autos where the frame is either cracked or the rear block broken completely out due to dry firing without the slide in place.
To reassemble:
1) place the barrel in the slide. It should be fully mated and locked into the slide.
2) Place the barrel bushing back in the slide around the end of the barrel, and then turn it so it's lined up.
3) Place the recoil spring back on the guide rod. Insert the spring into the hole under the barrel.
4) Compress the spring and place the guide rod end (with the small plunger on the end) so it barely catches on the notch on the bottom of the barrel. That should hold it in place. Be careful tho, the spring is under tension. Don't kink the spring when you compress it.
5) Align the slide with the rails and place the slide back on the frame.
6) As the slide gets to within about 1.5" of being completely on the frame you'll notice 2 small levers sticking up from the top of the slide in front of the hammer. Push down each of those levers as you push the slide further to the rear. Sometimes the slide will seem to catch and won't go further. It just takes a bit of giggling and persuasion but it will eventually go on smoothly. You should not have to force it.
7) Push the slide to the rear far enough to line up the notch in the slide with the front hole where the pin part of the slide lock/release can be inserted.
8) Fully seat the slide lock/release so the rear of it is in the rear notch.
9) Perform a function check. Remember that the hammer will not drop by the trigger unless there is a magazine inserted. If you want to try the trigger action be absolutely sure the magazine is unloaded before inserting.