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View Full Version : Adjustable Front Sight for Mosin-Nagant: How-To


Calamity Jane
May 18, 2002, 04:40 PM
Hubby has come up with something really cool, and I thought I'd share it with y'all. Following is the procedure, in his words:

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I do quite a bit of gunsmithing in my home shop on both modern and milsurp firearms. I’ve recently come up with a way to eliminate one of the common and frustrating problems with the Mosin Nagant. As we all know, Mosin Nagants generally shoot high - as much as five inches high at one hundred yards. Most of us enjoy shooting these rifles in their original military configuration without making a lot of alterations that take away from the history of the guns.

The method I’ve come up with for solving the high-shooting problem involves no permanent alterations to the gun (at least, nothing that cannot be easily and inexpensively replaced) and is almost un-noticeable (except, of course, for how much better the gun will shoot). The method involves replacing the front sight post with what you might call an infinitely adjustable post. By making this modification to the front sight, you’ll be able to easily and quickly adjust elevation point of impact for various loads and ranges.

Most people should be able to make this modification at home if they are accustomed to doing a little work on their guns. If not, find a friend who *is* so accustomed; or a gunsmith probably wouldn’t charge very much to do this, as it is a quick and simple operation requiring only the drilling of two holes and the tapping of one. The entire operation will take less than thirty minutes.

You will be removing the old front sight post, drilling a hole completely through the base of the sight in the position of the old post, drilling another hole that is perpendicular (at a right angle) to the first hole so that the two holes meet, and tapping the latter hole (the one that was drilled to be perpendicular to the first) with a 6-48 tap for a set screw to hold the new front sight post in place.

TOOLS YOU WILL NEED:

1. A small brass or other non-marring drift
2. A small hammer
3. Needlenose pliers
4. Possibly a small half-round file
5. 1/32 bit (approximate size, can be slightly larger)
6. A center punch
7. A small slotted screwdriver or appropriate hex wrench
8. A drill press (preferred) or an electric hand drill.
9. A #31 drill bit
10. A 6-48 tap (taper, bottom or plug) and a tap handle

NOTE: The #31 drill and the 6-48 tap can be inexpensively purchased from a supplier such as Brownell’s. Don’t even think about looking for these at your local hardware store.

MATERIALS YOU WILL NEED:

1. A length of suitable rod to fashion new sight posts
2. A 6-48 scope base filler plug screw (slotted or hex).

Here are the STEP-BY-STEP INSTRUCTIONS:

1. Using a small brass or wooden drift and a hammer, remove the front sight from the barrel.

2. Using a pair of needlenose pliers, gently work the old sight post back and forth until it breaks off at its base. If the post does not break off flush from its base, use a small half-round file to file it flush.

3. To drill the first hole: working from the top of the hood and using a 1/32 bit (approximate, but not much larger; you may want to slightly enlarge the hole later), drill all the way through the base of the sight in the position of the old post. This operation is most easily accomplished with a drill press, but it may be done with an electric hand drill if you are careful to drill as straight as possible. Remember to use a little light oil or cutting oil as you drill.

4. For the second hole: working from the rear of the sight (the side that faces the shooter), center punch the position of the second hole exactly in the center of the area between the bottom of the hood and the base of the sight. Using a #31 drill, drill this hole in the position made by the center punch down into - but not through - the hole you drilled in Step 3 above. These two holes, from Steps 3 and 4, will now be perpendicular (at right angles). IMPORTANT NOTES: (1) Do not use a drill larger than #31. This is the correct drill size for 6-48. (2) Be very careful to position your center punch mark *exactly centered* in the area described above because this area is quite narrow, and drilling just a bit too high or too low will cause the drill to break through the edge of the sight; and although it might “technically” still work to hold the set screw, it makes for a very unsightly job. ;) Remember that once this hole is drilled, it will need to be tapped, which will also slightly enlarge the diameter of the hole.

5. Now, you will proceed to tap the hole you just drilled (in Step 4) with a 6-48 tap. The 6-48 tap allows you to use a very common scope base plug screw as your set screw, and I believe most of us will probably have some of these. However, if you have a short 6-48 hex-type set screw, it would be even better, but the more common slotted one will work.

6. To make your new sight post: the post on my 91/30 measured .080 in diameter. I prefer a slightly wider post, so I used a piece of .095 welding rod. This is why you want to drill your initial sight post hole small so that it can be slightly enlarged if you prefer. Using the brass drift from Step 1, reinstall the front sight into its dovetail on the barrel. Screw in your 6-48 set screw a few threads. Cut a length of rod material approximately 1½ inches long, long enough so that it can be inserted through the top of the hood and bottom out on the sight base while still being long enough to slightly protrude out the hole on top of the hood. Mark the new post at a position slightly higher than half the inside diameter of the hood. Remove the post and cut at this mark. Reinstall the post and tighten the set screw firmly.

Voila! You now have an infinitely adjustable front sight post. By making posts of different lengths, you will easily be able to adjust point of elevation impact for various loads and ranges. You can also use the set screw to move the post up and down slightly for fine adjustment. You can change the post in less than ten seconds. In fact, the whole operation described above of making your new adjustable front sight takes much less time than it took me to write this How-To.

If you have any simplifications or improvements to this modification, I'd be happy to hear them.

Good Shootin’! :cool:

James K
May 18, 2002, 07:26 PM
Sounds like a good idea, but might be better to tap the sight hole also and use a screw type sight like the AK/SKS. Still infinitely adjustable and easier to keep in place since it can't just pop out. The 6x48 is OK but a 6x40 hex head set screw could also be used, and it is a more common set screw size.

Jim