Pre-1956 Marlin 39A adding aperture rear sight

Take a look at Lyman or Williams…they mount to the side of the receiver….

Examples: https://www.brownells.com/search/?search=Williams+foolroof+for+marlin+39. I am not saying these will mount to your specific rifle - just examples.

Do it right, go with a Marbles tang sight. It will use the existing tang screw (there will be a longer one to buy), and you'll need to drill one other hole ( are we sure there aren't two holes in the tang?). Marbles offers two sights for the 39. You will be much better served, and it is more period correct for your really nice old Marlin. And it will be an absolute tack driver with a peep; more sight radius, finer adjustment. Your barrel sight will have to be removed, or replaced with a folding one, regardless of what sort of aperture you get.
Moon

Hi General, You have one beautiful rifle there.

The normal and great solutions for an Model 39A, Skinners and Marbles, are indeed out of bounds as they need another hole. I agree with your principle of not drilling any more holes in your rifle.

This leaves Williams side mount sights. I'd recommend looking at photos of Williams sight enabled 39As, as I do not care for the blocky look. YMMV.

Keep us posted on your decision.

The Williams 5D sight is much less expensive and just as good for a hunting rifle. It doesn't have micrometer adjustments, but the lock screws work fine. If you lived nearby, I'd put one on for you, if we can find one.

The screw that you see on the top of the rifle is not to be used for mounting sights, it retains the top cartridge guide. If you don’t want to D&T the top of the receiver, the tang sight is the best option. You could possibly get by with the longer tang screw and a good adhesive such as Loctite 380 in place of the front screw.

You can use a williams 5d,Lyman or my personal favorite Marbles tang.You got your self a real beauty there.I have a 1955 39a it is nice but not showroom cond. they are real nice guns and are great investments.

General Geoff said:

Also as an aside, the magazine tube follower rod does not positively lock in place with an empty mag. If the rifle is sufficient jiggled around and muzzle pointed down, it can just fall out of the tube. Not something I want to happen with a 73 year old brass piece! Any ideas on how to better secure it? I'm thinking small O-ring slipped on the rod just past the knurled knob to keep the rod from rotating freely after being twisted into the lock notch of the tube.

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If I understand how this model's tube is constructed, I think your magazine spring is no longer putting enough pressure on the detent at the muzzle end to hold it. If you can't find and fit a replacement, perhaps just a little rubber band wrapped around the knurled end and the barrel will keep things together until you can figure out something better.

I think you'll like the Marbles tang sight -- I just mounted one on my Savage 99 a few months ago and it makes a big difference in the sight picture.

Kp321 said:

The screw that you see on the top of the rifle is not to be used for mounting sights, it retains the top cartridge guide. If you don’t want to D&T the top of the receiver, the tang sight is the best option. You could possibly get by with the longer tang screw and a good adhesive such as Loctite 380 in place of the front screw.

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This is absolutely correct. That screw holds the cartridge guide spring and they are not easy to find, be gentle if you remove it.

I also have a 1950 Marlin 39-A.
These early post-war rifles were not set up for use with a scope. They could be special ordered with the barrel drilled and tapped for a scope mount.

They were drilled and tapped on the side of the receiver for a receiver sight.
There are two plug screws in the sight screw holes, just under the rear screw that retains the ejector box.
Remove those two plug screws and a receiver sight bolts on.

The best of the receiver sights was the Lyman, but it's apparently been discontinued for the Marlin 39-A.
You can still find them for just over $100 if you do a search.

Second choice is the Williams Fool Proof which has click adjustments, or the Williams 5D that has locking screws.
I installed a Williams 5D on my rifle, but found a strange situation where the base was prevented from mounting flush to the receiver by the rear-most screw in the receiver. I had to remove some metal from the underside of the sight base so it would lay flat.

dfariswheel said:

Second choice is the Williams Fool Proof which has click adjustments, or the Williams 5D that has locking screws.

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The Williams sight is my first choice; the quality and workmanship is top notch. I have many of their sights installed on some of my rifles and have always found the Williams people to be very helpful and courteous. It should be noted that the FoolProof unit also has screws that lock the micrometer settings in place, which is why it was dubbed "foolproof". The 5D is essentially a FoolProof sans the micro adjustment feature and attendant price. I have one on my Model 39. It's interesting to note that the moniker "5 D" stood for five dollars; the price you paid for back in the day when I bought mine.

Nice looking rifle, General Geoff.

Shows them available direct from Williams ---?

When did Marlin thread the tangs? When did Marlin go to the threaded receiver top screws?

I'm still not sure of what the problem was with my 1950 Marlin other than that they may have made the rear receiver screw or the hole differently, but I had to remove a little metal from the underside of the Williams sight base that lays over that screw.
The screws domed head prevented the sight base from mounting flush.

I just shaved a little aluminum off that corner of the sight base so it would lay flat.

I wish I'd bought a Lyman receiver sight, it's more compact and doesn't stick out so far on the right side of the receiver.
Unfortunately it looks like Lyman discontinued it.

General, I've never found the tang sights to be an impediment to my grip; my thumb simply lands behind it. If memory serves, I had an aperture sight mounted on my 39 an eon ago; it is now long gone. It shot straight, but it was a damned tank for woods walking; wish I'd had their shorter, straight gripped carbine.
Dear heavens, Dave, that tang sighted Savage is really gorgeous. Wow!
Moon

3Crows said:

Shows them available direct from Williams ---?

When did Marlin thread the tangs? When did Marlin go to the threaded receiver top screws?

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My 1966-vintage 39A Golden Mountie has two screw holes drilled/tapped on the top of the receiver from the factory.



Stay safe.

You got the best of both..... drilled and tapped on the receiver top for a scope mount, and drilled and tapped on the receiver side for a receiver sight.
This is how Marlin did it from the later 50'st through the early 90's.

With the Marlin 39-AS with the rebounding hammer and safety they stopped drilling for a receiver sight.
So, Williams Sight Co made a special model receiver sight that mounted in the rear scope hole.

General Geoff said:

I found the Williams FP-39 in stock for a reasonable price so I went ahead and ordered that. As much as I like the aesthetics of a Marbles tang sight, my preferred grip style may be somewhat encumbered by it.

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I'm sure you'll like the FoolProof. I've used them since the early sixties, mounted on various rifles including a Remington Model 760, a Savage 99, Winchester Models 1886 and 94 as well as 5Ds mounted on a Marlin 39AS and a Beeman C1 air-powered carbine and have never had a lick of problems with any of them.
Tang sights might look nice, especially on classic lever-action rifles, and there's no denying that the extra distance between the front and rear sight helps the shooter be more accurate, but, like you, my hand doesn't get along with them; not even a little.

There are both Williams' and Lyman's side mounts out there. Took 5 minutes of Googling to find a few in stock...or so they claim. https://www.midsouthshooterssupply....receiver-inchpeepinch-sight-(fits-marlin-39a)

My appologies. Need to heed my own advice and read every post.

General Geoff said:

Well, I solved the mag follower tube problem with a small O-ring. Fits tightly now, and requires push & twist to unlock and remove it.
View attachment 1143183

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Brilliant!