These pistols are a basic Browning type design similar to the Colt .45 auto pistol. However, they incorporate many original features to simplify manufacturing processes and must be considered an advance over the original Browning patent. These pistols are often a little rough or crude in finish, but are well-made and of excellent design.
My take on Barnes's comments is that he's right on, with regard to facts, but "3 bags full" when it comes to "must be considered an advance over the original Browning patent." Here are my observations:
One thing that's a big simplification is the modification of the slide stop. In the 1911, it has a minutely intricate design that allows it to be retained without a clip. The TT33 uses a clip to retain the slide stop on the right hand side, which doesn't impact the utility of the weapon (it works just the same), is easier to manufacture, doesn't look as good, and raises the possibility of the clip getting lost during takedown.
Another attribute is that the entire hammer-sear mechanism is self-contained in its own assembly, which also includes the guide lips that control feeding from the magazine into the action. There are plusses and minuses to this arrangement. The plusses are:
The entire assembly can be replaced with another in the field by a relatively untrained person for quick repair.
The feed lips for the magazine are not so critical, since this machined assembly, and not the more easily damaged magazine, has the final control over feeding.
The disadvantages are:
The mainspring is necessarily small, making cocking the hammer a somewhat clumsy affair. The spring is very stiff in order to get the needed power to detonate the primer. Perhaps this was also made necessary by the same cartridge being used in the submachine gun PPHs 41, But given that the TT33 was developed a few years earlier, I'd think that this is unlikely. In contrast, the long leaf spring in the 1911 is much easier to thumb back and also the action is easier to cycle.
The assembly does away with any safety. This is a matter of disagreement amongst pistol shooters, as some do maintain that safeties are superfluous for military handguns. (This was also the view of the Polish cavalry, regarding the development of the Radom Vis 35 9mm.) In TT33 and derivative pistols imported into the USA, a safety must be fitted to import them, and both trigger and sear lock designs are used for these.
However, the bottom line for the TT33 as a carry gun is that you cannot carry it with a round in the chamber safely. If one uses the half-cock notch, dropping the pistol on the hammer can cause the half cock notch to fail, and at least one fatality has been recorded due to just this circumstance. The hammer cannot be carried down on a loaded chamber, since the designers did not see fit to copy the inertia firing pin of the 1911. This means that the hammer rests on the firing pin and the firing pin, in turn, rests directly on the primer.
For those fitted with a safety (like my Norinco "Tokagypt" copy in 9mm), I wouldnt' trust the safety as far as I could throw a bull by the tail, nor would I consider locking the trigger to be safe either, but if the half cock notch on the hammer is prone to fail, what can be said for the full cock notch.
I have posted similar sentiments on US gun sites in the past, only to be howled down by brave souls who inform me that they feel quite safe in packing a TT33 in their waistband on half cock.
To be blunt about this, my opinion is that in this circumstance, the weapon is not the only entity on half cock, if you catch my drift. But it's their life.
Another issue is that, as Barnes says, they can be crudely manufactured. Some of the examples I've seen (such as Polish-made versions) are finished very nicely, but often in the TT33 and its derivatives, keeping the machining process simple means that a minimal amount of metal is removed from the basic large part forgings. So, while the TT33 is quite compact for a weapon chambered in 7.62x25 or 9mm (being similar to a 1903 pocket pistol in this regard -- it is, for instance, a whole lot more compact than my Detective Special), it is also quite heavy for a weapon of its size.
I do think that it is quite strong and it will digest pretty much anything reasonable that you can feed it. If it is all one has, then it must be made to work. However, the main thing for me is the need to carry it without a round in the chamber, so that the slide must be cycled to bring the weapon into a ready-for-action state makes it undesirable for a carry gun.
On another subject, I'd also observe that the Soviet Makarov semi-auto pistol is commonly considered to be a derivative of the Walther PP design, a blowback action that is chambered for the 9mm Makarov cartridge, which is slightly more powerful than the .380 ACP.