M11/380 Registered Trigger in a PKM

[Alaska_Shooter]

Anyone seen these registered triggers before or know how they work?

https://www.gunbroker.com/item/1085298002

 

[john-g]

Looks like the one ernie wren sp? put together.

 

[Alaska_Shooter]

I thought his used a mac lower? This seems to use a weird registered trigger. It’s hard to tell from the pics

 

[slimshady]

Discussion on the trigger here:

Broadhead Armory F/A Trigger conversion for sale on Gunbroker

Someone asked about this a week or so ago. This is the full auto trigger to convert a Open Bolt Mac into F/A. http://www.gunbroker.com/Auction/ViewItem.asp?Item=76608829

uzitalk.com

Appears to convert an open bolt semi to full auto. Open bolt semis were declared too easy to convert because all you had to do was eliminate the disconnect function to get FA. This trigger would seem to do this.

A registered trigger and sear for a closed bolt is another possibility, since an unmodified FA open bolt drops right into semi autos. Just make a simple trigger and sear arrangement that uses the regular semi fcg pins and you have a legal FA only on a semi receiver host. Same principle as an M2 carbine conversion kit on an M1 carbine with less parts.

If ATf does allow this in any semi auto, it would seem to be pretty versatile. You just need to make a FA conversion set of parts to fit an unmodified semi receiver and incorporate this trigger.

 

[StenAtopia]

This reminds me back in the day when they were cutting Mac serial numbers and welding them on belt feds!!! 😉

 

[Alaska_Shooter]

Discussion on the trigger here:

Thanks for the link. It looks like they took it to new levels with the PKM

 

[strobro32]

For $150K, it's not finding a parking spot in my collection any time soon.

I shot Hoods PKM at his place and I liked it!

 

[KickStand]

I’ve got some hope that we’ll see an MG42 upper or another form of belt fed for the MACs.
Wasn’t one made back in the day but atf pulled some shady stuff and was able to get it to fire without the lower?

 

[Hill Raiser]

Discussion on the trigger here:

Broadhead Armory F/A Trigger conversion for sale on Gunbroker

Someone asked about this a week or so ago. This is the full auto trigger to convert a Open Bolt Mac into F/A. http://www.gunbroker.com/Auction/ViewItem.asp?Item=76608829

uzitalk.com

If ATf does allow this in any semi auto, it would seem to be pretty versatile. You just need to make a FA conversion set of parts to fit an unmodified semi receiver and incorporate this trigger.

That conversation is from 2007, but the GB listing references a 2015 ATF decision. I’d like to see the documentation to back that up. If true, would that not apply to those MK48’s that were made to use an HK trigger pack?

 

[Alaska_Shooter]

If you look at the GB pics they have a copy of the ATF letter

 

[Hill Raiser]

If you look at the GB pics they have a copy of the ATF letter

Face palm…..I admittedly did not look at all 58 pics. Thanks for the heads up

 

[MitchWerbellsGhost87]

Discussion on the trigger here:

Broadhead Armory F/A Trigger conversion for sale on Gunbroker

Someone asked about this a week or so ago. This is the full auto trigger to convert a Open Bolt Mac into F/A. http://www.gunbroker.com/Auction/ViewItem.asp?Item=76608829

uzitalk.com

Appears to convert an open bolt semi to full auto. Open bolt semis were declared too easy to convert because all you had to do was eliminate the disconnect function to get FA. This trigger would seem to do this.

A registered trigger and sear for a closed bolt is another possibility, since an unmodified FA open bolt drops right into semi autos. Just make a simple trigger and sear arrangement that uses the regular semi fcg pins and you have a legal FA only on a semi receiver host. Same principle as an M2 carbine conversion kit on an M1 carbine with less parts.

If ATf does allow this in any semi auto, it would seem to be pretty versatile. You just need to make a FA conversion set of parts to fit an unmodified semi receiver and incorporate this trigger.

The open bolt doesn’t drop in and function, the lower receiver has a sear block that prevents this. The lower would have to be modified for this to work. Not sure how they feel about sear blocks being removed from host guns. The m2 kits don’t require the host gun to be modified at all, it would be a different story with a closed bolt MAC. Same concept as cutting the blocking bar out of a semi Uzi and i think the alphabet boys frown on that kind of modification.

 

[slimshady]

I have only owned a semi 9 mm M11-nine so other models may be different?

I don't see any difference between a closed bolt and an open bolt except for a sear notch in the bottom of the open bolt and a fixed firing pin. In fact the semi closed bolt has the feed lip on the bottom and is a push feed just like the open bolt. Installing the open bolt fixed firing pin would convert it minus the sear notch. With no other mods you would now have a "stutter gun", cycle the bolt and it continues to fire until it empties the magazine.

There are no denial features on an upper, unless an open bolt is physically larger than the closed one it should drop in. Granted I've never had an open bolt but as I said the closed one is a firing pin away from conversion.

A more practical version would start and stop on command. You would only need to fabricate a trigger and sear mechanism that fit using the existing semi auto fcg holes to mount it. You could even use the existing hammer location with a notch in the rear of the bolt.

 

[MitchWerbellsGhost87]

I have only owned a semi 9 mm M11-nine so other models may be different?

I don't see any difference between a closed bolt and an open bolt except for a sear notch in the bottom of the open bolt and a fixed firing pin. In fact the semi closed bolt has the feed lip on the bottom and is a push feed just like the open bolt. Installing the open bolt fixed firing pin would convert it minus the sear notch. With no other mods you would now have a "stutter gun", cycle the bolt and it continues to fire until it empties the magazine.

There are no denial features on an upper, unless an open bolt is physically larger than the closed one it should drop in. Granted I've never had an open bolt but as I said the closed one is a firing pin away from conversion.

A more practical version would start and stop on command. You would only need to fabricate a trigger and sear mechanism that fit using the existing semi auto fcg holes to mount it. You could even use the existing hammer location with a notch in the rear of the bolt.

This is wrong. You CANT install an open bolt in the closed bolt semi. There is a sear block that prevents the open bolt from closing. As I mentioned in the previous post, the sear block in the semi auto closed bolt M11/9 is in the lower receiver. You have to remove the welded sear block from the lower receiver to install an open bolt FCG and for an open bolt to be capable of closing … with the location of the sear engagement notch on the front right end of the bolt, it would be impossible to make any kind of open bolt mechanism work in the closed bolt gun without removing that sear block from the lower. That is why they welded the sear block into the lower in the first place. Otherwise you could just drop an open bolt into the gun and let it rip and have a full auto 32rd run away. The sear block engages with the sear notch on the bolt to prevent the bolt from closing.

Otherwise you are correct, both guns use the same upper and the same bolt. Only difference between the semi bolt and the SMG bolt is the small sear engagement notch on the front and a fixed firing pin, which can be easily installed in the semi auto bolt, and the notch takes 3 seconds with a grinding wheel, but modification to the lower (removal of the sear block) is necessary.


Here is the sear block highlighted in red. It is welded in and sits in the same place as the open bolt sear, it engages with the sear notch on the open bolt assembly to prevent it from slam firing if an open bolt assembly is installed in the gun.





Some older models (from 83-85) have a different style of sear block, it was a plate that was welded in over the entire front end of the gun.

Both perform the same function. They prevent the end user from installing open bolt FCG parts, or using the incorrect bolt in the gun and getting a full auto run away situation like you describe.




Some of the guns that were sold as stripped frames in the early 90s by FMJ do not have the sear block and work well for making post sample machine guns without any modification, they even have the sear stud hole drilled, but all of the production completed firearms have these sear blocks installed so what you are describing is not possible in a closed bolt 11/9 without altering the receiver.

 

[brenbuilds]

This is wrong. You CANT install an open bolt in the closed bolt semi. There is a sear block that prevents the open bolt from closing. As I mentioned in the previous post, the sear block in the semi auto closed bolt M11/9 is in the lower receiver. You have to remove the welded sear block from the lower receiver to install an open bolt FCG and for an open bolt to be capable of closing … with the location of the sear engagement notch on the front right end of the bolt, it would be impossible to make any kind of open bolt mechanism work in the closed bolt gun without removing that sear block from the lower. That is why they welded the sear block into the lower in the first place. Otherwise you could just drop an open bolt into the gun and let it rip and have a full auto 32rd run away. The sear block engages with the sear notch on the bolt to prevent the bolt from closing.

Otherwise you are correct, both guns use the same upper and the same bolt. Only difference between the semi bolt and the SMG bolt is the small sear engagement notch on the front and a fixed firing pin, which can be easily installed in the semi auto bolt, and the notch takes 3 seconds with a grinding wheel, but modification to the lower (removal of the sear block) is necessary.


Here is the sear block highlighted in red. It is welded in and sits in the same place as the open bolt sear, it engages with the sear notch on the open bolt assembly to prevent it from slam firing if an open bolt assembly is installed in the gun.

View attachment 41018



Some older models (from 83-85) have a different style of sear block, it was a plate that was welded in over the entire front end of the gun.

Both perform the same function. They prevent the end user from installing open bolt FCG parts, or using the incorrect bolt in the gun and getting a full auto run away situation like you describe.

View attachment 41019


Some of the guns that were sold as stripped frames in the early 90s by FMJ do not have the sear block and work well for making post sample machine guns without any modification, they even have the sear stud hole drilled, but all of the production completed firearms have these sear blocks installed so what you are describing is not possible in a closed bolt 11/9 without altering the receiver.

This is correct. The M10 for example typically has a plate welded into the receiver from the bottom as well as a weld bead along the raised shelf. Some post samples were build by drilling the bottom weld and shelf weld, removing the plate, then welding the bottom closed for the sear stud to have an anchor point.


As for the this PKM conversion, I think it is grossly overvalued. While the PKM sear/ trigger linkage doesn't put too much stress on the trigger, the idea of a registered, cast MAC sear being the registered component is concerning. Original MAC parts are not metallurgically sound.

 

[slimshady]

OK, I believe you are misunderstanding what I am saying. No part of an OEM open bolt fcg would be used, I am referring to using the bolt only in a normal hammer fired semi lower. Does the sear block in the lower somehow extend up into the path of the bolt to prevent it from closing? If so, how? The semi bolt seems to be the same externally except for a section removed from the bottom right front to catch the sear on an OB, the semi has metal there. I am just going by pictures of the OB, maybe there is a feature on it I haven't seen that interacts?

In any event the closed bolt is easily converted to fire in open bolt configuration simply be keeping the firing pin extended. All it needs to control firing is a sear notch machined in somewhere.

And as I am reading it, the registered part isn't a MAC sear, it's an aftermarket trigger that is used. So OEM MAC quality wouldn't factor in.

 

[MitchWerbellsGhost87]

OK, I believe you are misunderstanding what I am saying. No part of an OEM open bolt fcg would be used, I am referring to using the bolt only in a normal hammer fired semi lower. Does the sear block in the lower somehow extend up into the path of the bolt to prevent it from closing? If so, how? The semi bolt seems to be the same externally except for a section removed from the bottom right front to catch the sear on an OB, the semi has metal there. I am just going by pictures of the OB, maybe there is a feature on it I haven't seen that interacts?

In any event the closed bolt is easily converted to fire in open bolt configuration simply be keeping the firing pin extended. All it needs to control firing is a sear notch machined in somewhere.

And as I am reading it, the registered part isn't a MAC sear, it's an aftermarket trigger that is used. So OEM MAC quality wouldn't factor in.

Yes. I explained this in detail in my previous post…. The sear block is supposed to catch on the sear notch if an open bolt assembly is installed. The closed bolt is rounded on the front end so that it smoothly rides over the sear block instead of catching on it (the same way an SMG with a worn sear notch runs away instead of catching on the sear) . It is designed this way so that an open bolt assembly cannot function in the closed bolt gun. Not sure how effective it is, tolerances on these guns are fairly loose and the sear blocks tend to vary in height a little bit, I’m sure there are instances where the open bolt can clear the sear block, but if you look at the shape of the block you can see how it was designed to replicate the shape of the open bolt auto sear so that it catches the bolt before it’s able to slam forward and close on the chamber.

 

[Gaujo]

Anyone seen these registered triggers before or know how they work?

https://www.gunbroker.com/item/1085298002

All that letter says (image 57, 58) is that they are approved for installation into any compatible semi automatic firearm without alteration to the receiver.

1) I have a hard time believing those triggers work in a standard semi auto PKM with an "un-modified receiver".

2) This violates the once a MG always a MG issue that comes with having to have an open bolt PKM host. This is the ruling that did Ernie Wren in when he fitted a MAC lower to a PKM. The ruling said you can't use an exiting machine gun as an upper that was in and of itself a machine gun originally as an "upper".

If one were able to design an all new gun that was semi auto closed bolt and became full auto with this trigger it might work, but this fails the logic test for me and I do not think that letter protects you at all.

 

[root]

If it were a parts kit 1st then it was just slag.

Cool gun but only 1500 worth of cool to me lol