Alaska_Shooter
Well-known member
- Joined
- Jun 23, 2004
- Messages
- 253
Anyone seen these registered triggers before or know how they work?
https://www.gunbroker.com/item/1085298002
https://www.gunbroker.com/item/1085298002
Thanks for the link. It looks like they took it to new levels with the PKMDiscussion on the trigger here:
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=76608829uzitalk.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.
Face palm…..I admittedly did not look at all 58 pics. Thanks for the heads upIf you look at the GB pics they have a copy of the ATF letter
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=76608829uzitalk.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.
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.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.
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.
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.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.
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.Anyone seen these registered triggers before or know how they work?
https://www.gunbroker.com/item/1085298002