M39 sights--Mojo rear only or front and rear?

[benEzra]

Anyone had any experience using the double-aperture Mojo sight set?

I am about to replace the standard rear with a Mojo unit, and was wondering if it would be worth it to replace the front with the Mojo front aperture as well.

How well does the double-aperture system work as far as accuracy and speed of acquisition?

 

[DMK]

I have both types of Mojo sights. I bought a dual arpeture set last month for my Sneak and just bought another set for my B-Barrel. Obviously I like them.

IMO, all the Mojo sights are of excellent quality. They are tough and well designed. The only drawback to them is that the rear arpeture is located so far foreward. This is a necessity of his design to keep them easy to install and to not require any permanent damage to these old rifles.

For me, the fact that the rear sight is so far foreward isn't as noticable with the dual arpeture setup as it is with the arpeture/post setup. You are basically sighting through a virtual tube, centering the front sight within the rear sight and centering the target within the front sight. It's easy to get a good sight picture quickly, and I find that it's very comfortable with my poor eyesight since I can put my focus on the target instead of on the front sight.

From what others have told me, the dual arpeture sights work best for target shooting and plinking. According to them, it's difficult to accurately hit a large target that doesn't center nicely in that front sight arpeture. That's second hand opinion though, I've only used mine to shoot paper.

 

[MuzzleBlast]

Does the Mojo rear sight by itself correct the foot-high grouping problem?

 

[DMK]

Does the Mojo rear sight by itself correct the foot-high grouping problem?

Well, not really. At 100 yards, either the Mojo or the stock sight is probably going to run out of adjustment. If your rifle shoots exceptionally high, I'd email Tim at [email protected] to see if he can sells a taller front arpeture sight.

The best fixes for Mosins shooting high are:

a) Shoot faster and lighter ammo. Wolf and S&B are mainly 180-200gr (although Wolf does sell a 147gr. I believe). A lot of the surplus is "heavy ball" also. Find some 147gr. ammo and it will usually shoot lower unless it's weak load.

b) If it's a Russian Mosin with the post type sight, put a piece of shrink tubing or one of those tubes for WD40 nozzles (or something similar) over the front sight post. Leave it long and trim it down to an acceptable POI with a razorblade at the range.

c) If you have a blade type sight such as on an M39 or Russian 1891, use some epoxy or JB weld to glue a tiny bead to the top of the front sight. (A brightly colored bead on top of the front sight centers very nicely with a rear Mojo BTW) Just make sure to degrease the sight (and scuffing if up with some fine snadpaper will help) to allow the glue to stick. There was some talk on a few of the forums about some guys making taller aftermarket M39 sights, but AFAIK, nothing ever came from it. The Finns made some but they are very rare in the U.S.

 

[benEzra]

Does the Mojo rear sight by itself correct the foot-high grouping problem?

According to their web site, the rear sight is adjustable for elevation:

The elevation setting of a Mojo sight is adjustable by means of a simple screw mounted forward of the aperture block, and gives a vertical range of about 36 inches at 100 yards. The screw is a 1/16" hex drive, and an appropriately sized hex key is supplied with each sight. We've found that hex-drive screws are far easier to adjust than the slotted screw found on some other sights. Ask anyone who's ever scarred the bluing on a favorite gun trying to engage a tiny slot with a tiny screwdriver.

That should be enough to get you on target.

I have found that the sights on my M39 are right on at 100 yd with the Wolf 148-gr FMJ. I think the original Finn issue load was 147-148 gr, so that's what the rifles are sighted for.

 

[DMK]

According to their web site, the rear sight is adjustable for elevation:

Sure, so is the original rear sight. The problem is these rifles were sighted in by the armorers for something like 300 yards. Often the front sight blades/posts are too low to shoot on target at 100 with the heavy ammo (172-200gr.) that the M39s prefer, even with the rear sights bottomed out.

I believe the Finn issue D-166 bullet was 200gr.

 

[benEzra]

I believe the Finn issue D-166 bullet was 200gr.

Let's see . . . yep. Doug Bowser says so in Rifles of the White Death. He also says this load was developed for the heavy machine gun, and that D46 issue ammo was loaded with a 170-gr HPBT. It is possible that both were issued to ordinary riflemen; Bowser doesn't say.

Looks like I was thinking of plain Russian ball, which was 148 gr (not coincidentally the weight that Wolf uses, since Wolf is made at Tula).

 

[Jaeger]

I bought a set for 1 of my K31s.

I was a little skeptical but I'll be darned if it doesn't work as advertised!
The K31s sights aren't too bad as issued but my groups tightened up considerably with the Phase 3 sights. (sub moa with handloads!)

You lose the ability to make quick elevation adjustments but for most of the shooting I do with my milsurps they are just fine. Actually, they are better than just fine. They are excellent!

My M48 is definitely getting a set!

Buy some. You won't regret it.

 

[DMK]

I just took my M-39 B-Barrel and Sneak out today to test some free floating I did on the Sneak and sight in the new Mojo on the B-barrel. Just for curiousity sake, I shot some heavy ball this time out. I had previously been using 147gr. Hungarian LPZS and 147gr. Czech Silvertip in these two rifles.

At 100 yards, I had to bottom out the rear sight on the Sneak and had maybe 1/4 turn up from bottomed out on the B-barrel, but both riifles shot right to POA with 180gr. Yugoslavian (which shoots pretty high and shoots to almost the same POI as S&B 180gr. SP). I had to crank the rear sight adjustment screw up about one full turn to shoot some Hungarian 172gr. Yellowtip, and about 1/2 of that for Albanian 174gr.(I think). I tried some Wolf 200gr. SP, but that grouped right up at the top of the paper and I couldn't get it any lower.

So, it appears that these sights will work just fine for the heavier bullets at 100yards.

BTW, with the Yugo Surplus, I got a 1.4" group with the Sneak and a 1.6" group with the B-Barrel using these sights. I've got to try some match ammo in these babies!