USAGOLD Posted June 2 Report Share Posted June 2 Interdynamic KG-9 9mm handgun that fired from an open bolt. I understand some are OK to sell and buy and others are not based on the serial number range. Anyone have any info on this firearm or can point me in the right direction. Quote Link to comment Share on other sites More sharing options...
Kevin Bartlett Posted June 2 Report Share Posted June 2 Not sure if this helps. You may have already seen this. It is my understanding that ALL of the open bolt guns are considered to be machine guns. I've been wrong many times before, so don't take my word for it. https://www.reddit.com/r/Tec9/comments/kom05q/interdynamic_and_intratec_history/ Quote Link to comment Share on other sites More sharing options...
Firelizzard Posted June 2 Report Share Posted June 2 I think the atf made everybody change to closed bolts to make it harder to convert like the mac's. You can still buy open bolt semi's , they just don't seem to pop up all that often that I see. Quote Link to comment Share on other sites More sharing options...
Thumpy Posted June 2 Report Share Posted June 2 They are legal to own Quote Link to comment Share on other sites More sharing options...
Raymoto Posted June 2 Report Share Posted June 2 I’m interested in a kg-9 if you are selling one Quote Link to comment Share on other sites More sharing options...
Chef Posted June 2 Report Share Posted June 2 7 hours ago, Kevin Bartlett said: Not sure if this helps. You may have already seen this. It is my understanding that ALL of the open bolt guns are considered to be machine guns. I've been wrong many times before, so don't take my word for it. https://www.reddit.com/r/Tec9/comments/kom05q/interdynamic_and_intratec_history/ No offense, but you are completely wrong. All of the open bolt semi-auto firearms manufactured before the AFT said "no more", are "grandfathered in" legal to possess and sell as title 1 firearms, just like any other, except of course that they are more sought after and therefore, more valuable than their closed bolt counterparts. 7 hours ago, USAGOLD said: Interdynamic KG-9 9mm handgun that fired from an open bolt. I understand some are OK to sell and buy and others are not based on the serial number range. Anyone have any info on this firearm or can point me in the right direction. Manufacturers were told to stop manufacturing open bold semi-auto firearms in 1982 (if my memory serves) by the AFT. So they did. Serial numbers are irrelevant because if it's an open bolt, it was made before the ban (unless someone did a closed bolt to open bolt conversion on one, which seems like a lot of work and expense, and therefore, unlikely). 1 Quote Link to comment Share on other sites More sharing options...
USAGOLD Posted June 3 Author Report Share Posted June 3 Thanks to all that responded, lots of good information 1 Quote Link to comment Share on other sites More sharing options...
Don. Posted June 4 Report Share Posted June 4 On 6/1/2025 at 7:23 PM, Kevin Bartlett said: Not sure if this helps. You may have already seen this. It is my understanding that ALL of the open bolt guns are considered to be machine guns. I've been wrong many times before, so don't take my word for it. https://www.reddit.com/r/Tec9/comments/kom05q/interdynamic_and_intratec_history/ Yes you are mistaken. Get a better source than the redditards…like here, for instance. Quote Link to comment Share on other sites More sharing options...
MPFiveO Posted June 5 Report Share Posted June 5 Well... I don't judge people for not having an intimate knowledge of how these things are classified, after all, the agency that makes up the rules changes them frequently. So, yes, in 1982 the ATF put out the ruling that open bolt firearms, particularly the Ingram type firearms, were too easy to convert to shoot automatically with a single function of the trigger. But, if you owned one manufactured before the arbitrary date, then it was grandfathered and legal to own. It could also be sold the same as any other semi automatic pistol with no other restrictions. So, while the MAC, Intratec, and certain others were grandfathered, certain others were not. The Spitfire was one such example. Sometime around 1968 they classified it outright as a machine gun. So, for a period the owners were allowed to register them but after the amnesty any remaining unregistered were considered contraband. I won't get into the details of how it's done but the open bolt MAC was just as easy to manipulate to fire automatically as the Spitfire, yet, they aren't required to be registered. So, in a nutshell, there's really only one source for the correct information, yet, if you ask them you're liable to get several different answers depending on who you ask. Quote Link to comment Share on other sites More sharing options...
OhioBrett Posted June 6 Report Share Posted June 6 You CAN manufacture open-bolt semi-automatic firearms, it's getting it actually approved that's the problem. The MACs had the problem that you could literally drop in full-auto parts and convert to an SMG. Other guns just a few seconds of file work. Quote Link to comment Share on other sites More sharing options...
jbntex Posted June 6 Report Share Posted June 6 On 6/4/2025 at 8:48 PM, MPFiveO said: So, while the MAC, Intratec, and certain others were grandfathered, certain others were not. The Spitfire was one such example. Sometime around 1968 they classified it outright as a machine gun. So, for a period the owners were allowed to register them but after the amnesty any remaining unregistered were considered contraband. The Spitfire didn't require any changes to the gun to fire full auto. You just held the trigger down and pushed the safety at the same time which prevented the sear from popping back up and catching the bolt after every shot. The KG9 and MAC s while really simple to convert you still have to modify parts of their fire control group and/or replace/remove parts that were quasi "permanent" to the receiver. MACs you could dremel off the top of the disconnector lever or remove it. However the sear/disco pin carriage was plug welded to the receiver so these parts just don't come out without receiver modification. Either way with the MACs and KGs you were modifying something (receiver FCG parts or bolt) where the Spitfire was a machinegun out of the box if you knew the secret handshake to make it rock and roll. I am guessing that is probably one of the reasons for the disparate treatment. Quote Link to comment Share on other sites More sharing options...
MPFiveO Posted June 7 Report Share Posted June 7 5 hours ago, jbntex said: The KG9 and MAC s while really simple to convert you still have to modify parts of their fire control group and/or replace/remove parts that were quasi "permanent" to the receiver. Actually, all that was needed was a slot in the bolt to clear the disconnector. The bolt would have then technically been the conversion part, but no modification to the receiver or parts. Not sure about the intricacies of the Tec-9 but with the MAC all one had to do was put a spacer behind the trigger. That put the fire control parts in a position where the sear would release the bolt but the bolt would ride on top of the disconnector and not be able to push it down far enough to disconnect from the sear. A buddy of mine has a registered Spitfire. When it transferred to him it hadn't been converted yet. We shot it some and were able to manipulate the safety and get it to fire some bursts. He quickly tired of trying to manipulate the safety and cut the disconnector. It's probably run through eight thousand rounds now and runs pretty much flawless. Quote Link to comment Share on other sites More sharing options...
jbntex Posted June 7 Report Share Posted June 7 There are a bunch of different ways to skin the cat on those guns, cutting the disco, slotting the bolt, etc. The MACs and KG both operate in a similar way where the bolt hits a disco that lets the sear pop back up with each shot and the sear and disco are quasi permanent to the receiver so you can't just dissemble the gun and remove the disco without leaving some trace of the modification. In both cases you are still having to actively modify the guns in some way to get full auto. Its somewhat similar to the PS90s that came with a Gen 1 or 2 hammerpack and which are a bent paperclip and 30 seconds away from becoming a fully functional machinegun but it still requires intent and modification on the owners part. Those Gen 1/2 PS90s, FN was clearly told to make changes to the guns and stop selling guns with packs that had auto/safety sears but the old ones were never rounded up and are still good to own. For similar reasons the open bolt MAC and KGs the Gen 1/2 PS90s command a price premium. The spifire was a little bit more of a toe over the line as it didn't require any mods and came from the factory capable of full auto out of the box which may be why it was treated differently. Quote Link to comment Share on other sites More sharing options...
Don. Posted Sunday at 05:15 AM Report Share Posted Sunday at 05:15 AM On 6/4/2025 at 7:48 PM, MPFiveO said: Well... I don't judge people for not having an intimate knowledge of how these things are classified, after all, the agency that makes up the rules changes them frequently. Nor do I. I do, however, judge people’s choices for information. The redditards are a very poor choice in that regard, as opposed to here. I clearly stated that much. 1 Quote Link to comment Share on other sites More sharing options...
Kevin Bartlett Posted Tuesday at 02:04 AM Report Share Posted Tuesday at 02:04 AM If you don't like my source of information, then that's fine. How about post a better source of information? I simply googled the Interdynamic story and the "redditard" link just happened to be one that seemed to show the basics of the Interdynamic story. I also clearly stated that I may be wrong. Okay, I was wrong. FWIW, a few years ago I was contacted by a friend who had a neighbor who died, and the widow found a "machinegun and silencer" in the attic. She just wanted it gone. I agreed to help and suddenly had to learn about early Interdynamic products. I never saw the suppressor, as it was sleeping with the fishes before I ever saw the gun. The gun now has a new dry, legal home. USAGOLD asked for information about a questionable gun, and I merely provided some info based upon my limited personal experience with Interdynamic products. As it turned out, my information was apparently not up to snuff. Reddit is not my number one source of information, and meaning no disrespect to Sturm, I've seen a lot of incorrect information posted here over the past 20+ years I've been here. Quote Link to comment Share on other sites More sharing options...
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