SKS Bolt Hold Open

A new reader e-mailed me about my SKS mods. It seems he has a Yugo M59…the model without the grenade launcher…and was interested in some of the things I’ve done.

During the discussion, he asked about the bolt mod that I did. I told him I would give him some more information (with pics) about how the bolt hold open system works and the purpose of the bolt mod. I was just going to e-mail it to him but I decided that any information that can be put out there should be made as public as possible…I bet there are other people out there looking for the same info.

With that in mind, here goes:

As I explained in the Bolt Mod post (linked above), the problem with using detachable magazines with the SKS is that many of the aftermarket mags do not operate the bolt hold open latch. That means that the bolt does not stay open after the last shot. This is a serious issue because the bolt has rails at the bottom that lock into the feed lips of the magazine. That means that, to change mags after the last shot, you have to open the bolt and hold it open with one hand while using the other two hands to operate the magazine release catch, remove the dry magazine and insert a fresh one, then the bolt can be released again.

Actually, you can do it with only two hands, as long as you are independently wealthy and can afford to replace all the magazines you beat up by dumping them on the deck when changing mags.

Either way, this is an issue. Basically, it means that a modified SKS is not very practical for use as a homeland defense rifle and is only really suitable for use as a “fun gun” at the range. A “sort of” fix for this problem is the bolt mod that I described in my earlier post. All you do is grind off the rails at the bottom of the bolt that catch on the magazine feed lips. That enables you to change mags without opening the bolt.

It is not truly a fix because there are still issues. You can’t load your mags to max capacity because inserting the mag with the bolt closed causes the rounds to push down into the magazine. With a fully loaded mag, this is often very difficult if not impossible. Some magazines feed lips allow the rounds to move around too much which causes the top round to shift and jam up the works when attempting to insert a loaded mag with the bolt closed. Having the mod is better than not having it but it is not utopia.

After completing this mod, I purchased a 20 round “polymer” (read plastic) mag from Tapco. Lo and behold, at least on my rifle, the Tapco mag actually operates the bolt hold open latch.

Here’s how it works.

The follower in the magazine (the part that pushes up on the bottom round) has a small “tail” that sticks off the back end.

With the magazine loaded, the follower is pushed down into the magazine so that the “tail” is down inside a groove in the magazine.

Here, only one round is loaded so the “tail” is sticking up a slightly, a second round placed on top of the first would push it down completely into the mag.

Once the last round is stripped into the chamber, the tail sticks up as high as it will ever go.

That “tail” pushes the bolt hold open latch up. After that last round is fired and the bolt cycles back, the bolt hold open latch is pushed into the bolts path.

When the recoil spring pushes the bolt forward, the face of the bolt catches on the latch, locking the bolt open.

This is just a reference photo to show you what part of the rifle we’ll be looking at. I hate it when I’m given closeups for illustrations and they just assume you know what general area you are supposed to be looking in (car manuals are notorious for this).

We are going to be looking up through the bottom of the magazine well.

This is with the bolt locked back. The bolt hold open latch is in the way of the bolt, the bolt is making contact with the latch at the arrow, holding it from moving any farther forward.

There is a small metal tab on the face of the bolt hold open latch. This tab is what the “tail” of the magazine follower pushes on to raise the latch into position to lock the bolt open.

The bolt hold open latch is actually held in the unlocked position by a weak spring. It is the tension of the bolt, being held firmly against the latch by the tension of the recoil spring, that keeps the hold open latch in the locked position.

To release the bolt, all you have to do is pull slightly back on it, as soon as the tension on the latch is released, the spring will push it out of the way of the bolt (in the direction of the arrow) and the bolt will close.

To lock the bolt open without a magazine inserted, put your finger up into the rear of the magazine well. You should be able to feel the tab sticking off the bolt hold open latch. Pull the bolt to the rear while putting upward pressure on the latch, as soon as the bolt clears the latch, the latch will slide up and the bolt can be released. It will catch on the bolt hold open latch thereby locking the bolt open.

This is a different perspective with the bolt locked open again. The pencil is pointing to the hold open latch.

Again with the bolt closed, the pencil is pointing at the latch.

If your bolt hold open isn’t working with your magazines, either the “tail” on the magazine isn’t positioned correctly (or it simply doesn’t have one) or the tab on the bolt hold open latch that the “tail” is supposed to press on is worn or possibly broken off.

Numrich Gun Parts has the bolt hold open latch for $7.05 if you need to replace yours (I would imagine that this particular part is the same for the model 59 but I make no guarantees and offer no promises…Numrich also has parts listings for the Type 45 and Type 56).

The arrows in this photo are pointing to where the rails on the bottom of the bolt SHOULD BE had I not ground them off.
the gaps where the arrows are enable the magazines to be removed/installed with the bolt closed…usually…with some difficulty…depending on your magazines…your mileage may vary.

The best all around magazines I’ve found to date are the Tapco 20 rounders. They feed flawlessly, they install the most consistently with the bolt closed and they operate the bolt hold open latch so I generally don’t have to worry about them working with the bolt closed.

I hope this cleared some things up for the reader who originally asked the question, as well as anyone else happening upon my humble little corner of cyberspace. If any of my explanations or photos were unclear, and you are still unsure how this works, feel free to let me know in comments or shoot me an email and I’ll try again.

6 thoughts on “SKS Bolt Hold Open

  1. thanks for the info. I have heard of the problems associated with detachable mags for the SKS; this clears up a lot of those issues. Thanks again

  2. I have a 30 rnd. mag. and was wondering if it is possible to take the follower in the magazine (10 rnd) and swap them. there is some difference in size,just unsure if there would be to much slop for the 10 rnd tail on the follower.

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