Operational Racheting Top Cover for Semi

[suka5168]

The old notion that "you must first disable" the Racheting Top Cover for use on a semi is now History. Although it was designed as a safety feature on Open Bolt F/A; It is a neat little feature to have during Cease Fires or a Cold Range.

This modification requires the center slot to be blocked near the rear. A piece of scrap sheet metal around .075" (I just used a piece of scrap AK receiver) is welding between the slit. The length of the piece is about 3/4 of an inch.

I used a MIG and just welded the end and front edges. Be careful as the piece of metal is thin and can melt right thru. The weld joints does not need to be pretty as the Cover Plate will hide the welds. Grind of any excess splaters or spurs.

Reinstall the racheting mechenism for proper fit. Place the bolt back in the channel and retest. It should engage about 5-7 teeth before reseting.
I am not to sure if the regular semi buffer does get in the way, since my leftover scrap buffer is only 1".

Have fun with a new Bolt hold device.
This was made for the IDF semi Uzi

[suka5168]

Left to Right:
Semi Cover
Modified Racheting Cover
SMG



Below Top to Bottom:
SMG
Modified Racheting Cover
Semi

[RoverDave]

Great idea suka!

[watchin]

For those who don't weld, are there any other thoughts on this concept? By accident I noticed that I like the ratcheting hold open feature that the F/A top cover provides. I can see from your detailed photos how and why it works the way it does and maybe welding is the only way to block the mechanism from locking up. It does seem like the bolt is fully open when it is pulled all the way back. How do you release it with your modification? What allows the ratchet pawl to disengage when only partially pulled back? Great job on the modification, by the way.
-watchin-

[TimW]

To resurrect a thread, what's the problem using an unmodified FA Top Cover? You can pull it back far enough to hold the bolt open during cease fires..that seems obvious enough. But what's the problem with the extra open-length?

[tacdrivrnc]

with the regular FA ratcheting cover you can't pull the semi auto bolt back far enough to disengage the ratchet mechanism because the semi auto buffer prevents the bolt from going back that far.

[TimW]

How much is it short of being able to go all the way back? I know that the rear buffer is needed for the striker, but is there any way to shorten the buffer enough to accomplish this?

[cvasqu03]

How much is it short of being able to go all the way back? I know that the rear buffer is needed for the striker, but is there any way to shorten the buffer enough to accomplish this?

I actually one thought it might be possible to simply use a needle file and cut notches into the SA non ratcheting topcover and install a ratcheting mechanism on it. Never got around to trying it since I was busy trying to get my cheap rail project off the ground.

Has anyone else tried doing it this way? Does anyone know of reasons why this wouldn't work?

[ruskiegunlover]

To revive this, has anyone tried the last idea?

[solartj]

To revive this, has anyone tried the last idea?

A buddy of mine had his Hard Times Armory RR Uzi brought up to spec by Vector. One of the things Vector did was notch the original semi top cover. If you look at the old Group Ind. price list, you'll see that was part of their conversion too. http://files.uzitalk.com/reference/p...Idocuments.htm

[Delta Bravo]

How much is it short of being able to go all the way back? I know that the rear buffer is needed for the striker, but is there any way to shorten the buffer enough to accomplish this?

Is this safe to do?

[thenorm]

with the regular FA ratcheting cover you can't pull the semi auto bolt back far enough to disengage the ratchet mechanism because the semi auto buffer prevents the bolt from going back that far.

Sorry, I'm new to the UZI madness..

I'm not able to picture it. You say that the Semi isn't allowed to go back far enough on the SMG ratchet cover. So why does the modification shorten the slot?

I'm about to start a mini semi build, and I'd like to have the ratchet if possible.

Thanks

[Golovko]

Due to the way the ratchet mechanism works, it needs to reach the rear of the slot to disengage. The ratchet is engaged when the ratchet mechanism contacts the front edge of the slot, and remains engaged until the ratchet mechanism contacts the rear edge of the slot. It then remains disengaged until it reaches the front of the slot again. Because of the buffer in semi-auto Uzi's, the slot on an SMG topcover is way too long in relation to bolt travel. Because of that, it is not possible for the bolt to travel far enough rearward to allow the ratchet mechanism to reach the rear of the slot on an SMG topcover. So, the fix is to move the rear of the slot forward, so that the ratchet mechanism can reach it.

[thenorm]

Due to the way the ratchet mechanism works, it needs to reach the rear of the slot to disengage. The ratchet is engaged when the ratchet mechanism contacts the front edge of the slot, and remains engaged until the ratchet mechanism contacts the rear edge of the slot. It then remains disengaged until it reaches the front of the slot again. Because of the buffer in semi-auto Uzi's, the slot on an SMG topcover is way too long in relation to bolt travel. Because of that, it is not possible for the bolt to travel far enough rearward to allow the ratchet mechanism to reach the rear of the slot on an SMG topcover. So, the fix is to move the rear of the slot forward, so that the ratchet mechanism can reach it.

I see now, the back of the slot works the ratchet release. Most ratchet designs work off of the teeth ending or another feature on the teeth side of the slot.

Thanks for the details, I'm going to look at that for my build.

[WhisperFan]

I bought a QD stock that came with a SMG ratcheting top cover.

Since I didn't need the top cover, I got to playing around with it. I took it apart, removed the ratcheting pawl and spring. I put it back together and I found that it slides easily and looks like it will work fine on a S/A.

I can't imagine that no one else has ever done this - if you have, have you experienced any problems ?

[RoverDave]

I bought a QD stock that came with a SMG ratcheting top cover.

Since I didn't need the top cover, I got to playing around with it. I took it apart, removed the ratcheting pawl and spring. I put it back together and I found that it slides easily and looks like it will work fine on a S/A.

I can't imagine that no one else has ever done this - if you have, have you experienced any problems ?

Yes, many people have done it and it works fine. The modification described above is only needed if you want to preserve the ratchet machanism for use on the semi-auto.

What did you use the QD stock on? Hopefully not a semi-auto UZI Carbine.

[WhisperFan]

What did you use the QD stock on? Hopefully not a semi-auto UZI Carbine.

No - I am saving the QD stock for after I SBR the carbine. But the price wasn't bad, so I bought it now.

[watchin]

You can use the QD stock you got but you have to change it to a permanent mount stock. It's not that hard to do. As for the ratcheting top-cover, you didn't read the opening post to this thread. It is all about NOT having to disable the ratchet pawl.
Anyway, a good reason for the ratcheting type top cover on a semi is if you ever buy a drum magazine. The bullets don't compress in it like they do in a stick mag so inserting the drum is much easier if you can lock open the bolt.
Having said that, I have to get busy and modify my smg topcover for a semi and prove this out.
-watchin-

[dannyk45]

Just wondering if anyone has tried this top cover project with positive results.

[rgrprib]

So, the question remains. Has anyone done this, and does it function correctly?

The one thing I noticed is the buffer block seems to be the negating factor that does not allow the bolt to move the rear far enough to allow the ratchet to disengage. Could/would it be acceptable/safe to cut down the buffer block to allow the bolt to travel further back, to allow the ratcheting mechanism to disengage? Would this have a negative impact on function? - Bolt travel etc.

Just a thought.

Prib