Semi-Auto open bolt question


February 11, 2011, 09:43 PM
The main question is dose anyone make one?

I was talking to a fellow gun guy tonight and we were talking about the old Thompson's. I believe the older Thompson semi's did fire from an open bolt, I could be wrong. Anyway I got to thinking and I can't think of a single current production gun that fires from and open bolt. Honestly I can't think of one that has been made since they changed the Thompson's.

Does anyone make one,if not what was the last? Would it be legal to make one?

Just curious,

If you enjoyed reading about "Semi-Auto open bolt question" here in archive, you'll LOVE our community. Come join today for the full version!
February 11, 2011, 09:47 PM
Open bolt firearms are controlled under NFA, as ATF considers them "readily convertible" to full auto. If produced prior to the ruling (1982, IIRC) they are grandfathered.

February 11, 2011, 09:47 PM
ATF decided it was too easy to convert them to full auto - that's why there are no more new production designs.

February 11, 2011, 09:54 PM
The BATFE is kind of down on guns that fire from an open bolt nowadays, saying that they're too easy to turn into full auto machineguns. There have been a couple that were made as pistol calibre carbines, but they have been out of production since the 1980s, at least. Several of them were designed to bear a superficial resemblance to the Thompson, anyway.
All selective fire versions of the Thompson fire from an open bolt, and all the semi-automatic only version fire from a closed bolt.

February 11, 2011, 10:12 PM
I knew the ATF decided it was too easy to convert the Thompson's to full auto, but I was unaware that they had that opinion of ALL open bolt designs. That pretty much answers my question I guess.

February 12, 2011, 08:54 AM
Its not as if its out of the realm of possibility to convert closed-bolt weapons to full auto, or to bump fire nearly any gun with a decent trigger. Just another way to ban guns.

I mean, if its a crime to do something (convert/own full auto post-86), why are they banning things just because they could possibly be used in a way that causes a crime? It's one of those slipperly slope logic curves that we all know and love about the ATF.

451 Detonics
February 12, 2011, 09:00 AM
I will also add to this that the guns that fired from an open bolt suffered somewhat in accuracy because of it. Having that heavy bolt slam forward at the instant of firing does not help in keeping the sights precisely on target.

February 12, 2011, 09:22 AM
There were a lot of MAC style semi open bolts. One has to ask, despite being as close to "the real thing" why you would want one? Easy to convert? To someone that knows how to run shop equipment they all are not difficult. Glock conversions simply replace the playe at the rear of the slide. The only catch is that you have to have the proper FFL and SOT before you play, so you don't get locked up.

February 12, 2011, 09:45 AM
One has to ask, despite being as close to "the real thing" why you would want one? Easy to convert?

I wouldn't want one, especially considering what 451 Detonics said about accuracy, it really does make sense that they would be very hard to keep on target. I was just curious as to why there aren't any, and what happened to them.

February 12, 2011, 10:01 AM
An open bolt gun really isnt all that hard to shoot well with, and they can be shot surprisingly well, especially if they have a stock, it just takes some getting used to. Still, a closed bolt does make it easier.

The open bolt "pistols" on the other hand, like their closed bolt counterparts, dont do as well, and especially the MAC type guns.

Carl N. Brown
February 12, 2011, 10:48 AM
Some of the early Mac10 semi-autos fired from open bolt and were very easily converted. They were quickly banned by ATF.

The "Tommy gun look alikes" sold as Spitfire and Apache fired from an open bolt (they actually used surplus M3 grease gun bolts in a tubular receiver). One could fire full auto if you pushed up on the safety while pulling the trigger (some question as to whether that was a "bug" or a "feature"; ATF decided it was a deliberate feature and banned the guns.)

All AutoOrdnance (Numrich and later Kahr Arms) semi-auto brand-name Thompsons were designed as closed bolt semi-autos and are very, very difficult to convert to full auto.

ADDED: The original 1927 Thompson Model 1927 was just a Model 1921 submachinegun with a plug in place of the selector (full/single) switch. The original 1927s were often converted by police armorers back to 1921 SMGs by simply swapping out 1921 fire control group parts. They also had 10.5" barrels. When semi-auto Thompsons were introduced in the 1970s, Numrich, later Kahr Arms, used the designation Model 1927 but they have always been a complete semi-auto redesign, with no internal parts in common with the original Model 1927. That may be the source of the question.

If you enjoyed reading about "Semi-Auto open bolt question" here in archive, you'll LOVE our community. Come join today for the full version!