Closed Bolt Pistols?

[StraightOuttaAmmo]

Does anyone know why there aren't really any closed bolt pistols? (Excluding anything fitted with a "stock" or sig brace, like an AR pistol) Why aren't there any normally sized handguns that are operated with a close both system? I feel that a closed bolt system could have some advantages. Any thoughts?

[Jim Watson]

I do not know of a pistol with a open bolt.
What are you talking about?
Do you want a pistol with a bolt as distinct from a slide?
Like a Ruger, Luger, Mauser, etc.?

[StraightOuttaAmmo]

I'm not looking to buy one or anything, but am just trying to see what pistols are out there that are operated with a closed bolt system, instead of the sue of a slide. Kinda like a Mauser or Luger. They are not common except for rimfire pistols. I'm trying to see if there are any advantages or disadvantages. Also are there any thoughts on a larger caliber bolt pistol.

[Jim Watson]

I figure the marketplace has answered that.
The internal bolt autopistols have come and gone except for a few target pistols.
The last I can think of was the Wolf Ultramatic best known for being complicated and heavy.

The Automag was about the best modern example of the type, now collectors items.

[StraightOuttaAmmo]

That is a good point, very few have been popular or produced in high quantity . Why do you think this is? Maybe over complicated, and expensive?

[dakota.potts]

There are several .22 caliber pistols with this type of mechanism. I assume this is to lighten the slide for operation with light charges.

For what it's worth, the Luger is somewhat unique in being a toggle lock system which I'm not aware of in any other modern pistol

[StraightOuttaAmmo]

For sure! The operation of these pistols seems to work great, but the question is why aren't they popular besides the Ruger Mark series?

[Sevens]

I'm not sure what you believe the Ruger Mark I-II-III does differently than most ANY rimfire semi-auto pistol does...? It's the same. The Ruger happens to have a tubular shroud over the bolt that is doing the work but essentially and mechanically, it's doing exactly the same thing as Browning's original concept that became the Colt Woodsman.

As for a center fire pistol that runs an internal bolt that actually locks in to place (like the rare Wolf mentioned above) my best guess as to why we don't see more of them is because when the rubber meets the road, they end up being the long way around. More costly, more finicky and more oddball -- but offering little to no tangible advantage.

The Desert Eagle uses a bolt (looks very much like an AR-15 bolt) and while it also uses a reciprocating slide, the bolt is indeed a separate part from the slide.

[dahermit]

I don't know if this is what you are talking about, but Remington used to make a bolt action handgun called the XP-100 in .221 Fireball.

[Sharkbite]

Styer SPP???

[44 AMP]

Does anyone know why there aren't really any closed bolt pistols?

Nearly all semi autos are "closed bolt" systems.

Understand the terms, "closed bolt" and "open bolt".

"bolt" refers to the breechface of the bolt, or, slide, and where it is positioned when you pull the trigger.

OPEN BOLT is the system found in most submachineguns and machineguns today. The bolt is open (back), chamber empty, and it feeds a round, closes and fires when you pull the trigger. There are a small number of open bolt pistols, semi auto versions of SMGs, and they are both very difficult to fire accurately and frowned on by the ATF.

Closed bolt means the action is shut, a round is in the chamber, when you pull the trigger. This is the system used by nearly every semi auto pistol and rifle. It is also the system used in many select fire weapons. (M16, AK 47 etc)

The WWII select fire German FG42 is a very unique system, operating closed bolt for semi auto and open bolt in full auto mode.

Why aren't there any normally sized handguns that are operated with a close both system? I feel that a closed bolt system could have some advantages. Any thoughts?

The answer is, there are, nearly ALL of them are closed bolt. You have mis-applied the term. What is it you are trying to ask? Why do many use slides (without a separate bolt?)? Ease of manufacture and functionality is the main reason.

[StraightOuttaAmmo]

When I say closed bolt, I am meaning a INTERNAL close bolt system, without the use of a external slide. I know the difference in open and closed bolt. I just forgot to mention internal. I was asking what I said above, Why don't these seem to be popular? Maybe because of over complication or too expensive?

[tirod]

Asked and answered - overcomplicated and too expensive.

It was pointed out there are almost none on the market - which goes to the engineers, accountants, and owners of firearms companies looking at profit projections on a new design balanced by the potential sales.

Basically the bolt would be housed inside a cover which would add to the nonfunctional dead weight of the entire package. It's contrary to the purpose of better engineering, which is called "elegance" in the trade. Designers and engineers try to get a part to do MORE than one job to reduce complication and the number needed to get it done.

That's why the extractor is usually part of the bolt face design - instead of some separate mechanism. And why the firing pin goes thru it, too. Otherwise it would be a shuttle door sealing the chamber and doing nothing more - which is how the LSAT "caseless" actions are designed.

So, divorcing the slide from the bolt would mean having a kind of an AK cover over the existing bolt assembly under it. In a handgun that would be inefficient and create complication, where using the slide, it's mass, and the other things it can do would be more elegant - ie, efficient. That cover would also need to be soundly mounted for the rear sight, adding to the number of extra things it would have to do. Typical modern handguns just use a dovetail on top for whatever sights are added. Dirt simple and adds to the multifunctionality of the one part.

Move the hammer spring and wrap it around the firing pin with it's own sear, and you add another function to the slide eliminating a separate mechanism with it's exposed hammer. It's arguable how we appreciate that but it's definitely mechanically elegant and refined, plus the grip is no longer constrained in it's shape to house it. The firing pin assembly does it's own motivation, not from some external separate parts.

The more separate parts you have, the more can go wrong, and the higher the potential risk of malfunction. On the other hand, the more refined the part doing more jobs, the more likely it can be made wrong and increase cost if it has to be scrapped. There are offsetting disadvantages that only modern precision machining can prevent.

It's why some of us look at the AK47 as a near third world low tech design which only requires basic "machine age" ability, vs the M16's high tech alloy and composite design which integrates the function of a piston and gas cylinder into the bolt carrier making the design lighter with fewer moving parts. Not to forget the barrel extension which eliminates pressing a barrel into a trunnion while simultaneously setting headspace. The M16 simply screws the extension on like a micrometer. It's then pinned into the threads to set it.

Elegance. Another way to say it is "smarter."

[Skans]

The answer is, there are, nearly ALL of them are closed bolt. You have mis-applied the term. What is it you are trying to ask? Why do many use slides (without a separate bolt?)? Ease of manufacture and functionality is the main reason.

Ahhh, now I understand what he is asking! I had the same problem trying to figure out how he thought most handguns are "open bolt"

The answer is that handguns can be made smaller, more compact and more efficient using a slide that incorporates a bolt. There are examples of true bolt (non-slide) pistols, but they tend to be quite large:

M10 (Mac 10)
Sites Spectre
Encom MP45
Claridge Hi-Tec
Wilkinson "Linda"

These are all pistols, but quite large and they all have fixed barrels. Smaller Guns like the Luger, and maybe even the Lahti are, quite frankly, a weaker design that doesn't hold up to the pressures and stresses we put on modern handguns.

[carguychris]

Aside from production economy from reducing parts count, the primary reason why most automatic pistols use slides rather than separate bolts is that it's a more efficient way to ensure that the breech stays closed long enough on firing.

Most pistols use recoil operation; in such a pistol, the breech is held closed by a combination of recoil spring pressure and the momentum of the reciprocating assembly. If the recoil impulse remains constant, the spring pressure must increase as the mass of the reciprocating parts decreases. A slide-equipped pistol can fire the same cartridge in a smaller and lighter overall package because the slide provides the mass required to keep the breech closed, without the need for a housing.

I'll cite 3 contrary historical examples to illustrate why this approach is popular.

• The Astra 400: 9mm pistol with uses a slide, but utilizes simple blowback operation rather a locked breech, thus requiring a very stout recoil spring. The pistol is notoriously difficult to operate due to the high slide operation force.
• The Lahti pistol: 9mm design with a separate bolt. Notable for its large size and heft—it weighs ~44oz loaded despite holding only 8+1 rounds. There's some dead weight there somewhere.
• Clement pistols and the closely related S&W Model 1913: Pocket blowback .32/.35 pistol with a separate bolt. Required such a stiff recoil spring that the designers wound up incorporating a mechanism to disengage the spring so the pistol could be loaded more easily—IMHO a perfect example of how a theoretically simple but fundamentally flawed design ends up being more complex once the underlying flaws are addressed.

AR and AK style pistols and a few other outliers like the Desert Eagle and Wildey use gas operation to open and close the bolt and thus don't rely on breech block mass. The disadvantage here is that the gas system adds weight, size, and complexity, preventing these pistols from being truly handy or compact.

[44 AMP]

Both the Wildey and the Desert Eagle are kind of "half breed" designs, in that they have both a rotating multiple lugged bolt head AND a slide. They are not a true "bolt within a receiver" like the Broomhandle Mauser, the Luger, or the Ruger Mark series .22s.

The original Auto Mag, is a "bolt within..." (in this case a barrel extension), and is recoil operated.

[carguychris]

Somewhere in the back of my head, I knew that about the Wildey and DE.

Also, in terms of using a bolt within a receiver, both the Luger and the Lahti operate a bit differently than a Ruger in that the barreled receiver and bolt move as a unit before the bolt disengages. Another example of this approach is the Nambu.

[Theohazard]

I think I the answer to the OP's question is that a slide allows the pistol to be shorter and more compact, and also simpler. The slide is a telescoping bolt, which puts much of the bolt weight in front of the breech. Some .22 pistols like the Ruger Mk III can get away without using a telescoping bolt because the bolt doesn't need to be very big. But without a telescoping bolt, it would be pretty hard to make compact centerfire pistols.

[Jim Watson]

The Bergmans have internal bolts, with room made for a big enough bolt by putting the magazine in front of the trigger like a Mauser.

The graceful Gay Nineties Schwartzlose is a "hybrid" rotating bolt in slide design akin to Wildey and Deagle.

[44 AMP]

both the Luger and the Lahti operate a bit differently than a Ruger in that the barreled receiver and bolt move as a unit before the bolt disengages.

because the Ruger .22LR is a straight blow back action, the others are not, they are locked breech actions. Something has to move (other than the bolt) in order for the bolt to unlock. With recoil operated actions, the bolt (and its carrier if there is one) and the barrel move together for a short distance, then unlock, the barrel stops and bolt (slide etc.) continues to move, cycling the action.

With gas operated systems, the barrel doesn't move, but the gas system DOES, to unlock the bolt and allow it to cycle.

[testuser79]

The Bergmann-Bayard, C96 Mauser and Nambu had this arrangement, like a rifle. Bill Ruger was impressed enough that he used the Nambu to inspire his popular .22 handgun.

Machine pistols like the micro Uzi and VZ61 Skorpion use the same configuration. When mounted with a stock this type of weapon has a purpose, otherwise, it looses a lot of utility and becomes and overweight pistol.

Anyway, we've talked about disadvantages...weight, size, etc. One strong advantage: It's a much more stable platform for mounting optics and decent way of designing a small pistol caliber carbine. If it wasn't for SBR laws a micro machine pistol sized carbine around 3 lbs would probably sell very well.

[44 AMP]

Bill Ruger was impressed enough that he used the Nambu to inspire his popular .22 handgun.

I have often heard this, but have never seen where Ruger himself said it. Have also heard it was the Luger, not the Nambu (obvious name similarity), and I have found where Ruger made a hand drill before he got into making firearms, and that drill has a grip shape almost identical with the Ruger .22 pistol.

Since he's not around to ask anymore, I don't think we'll ever really know.

[Scorch]

Pistols with a rotating bolt
Desert Eagle
Beretta PX4 (kinda, actually the barrel rotates)

Both unnecessarily complicated, both are unnecessarily expensive. But virtually ALL modern pistols fire from a closed bolt.

And if you want to see where Bill Ruger got the idea for the Standard Auto, look at a Glisenti.

[barnbwt]

Steyr TMP/SPP/B&T TP9/MP9 has a rotating barrel, and bolt body that is basically a slide --I bought mine at a sharp discount since it was missing the entire 'upper reciever,' but could still fire the thing safely since the bolt is fully constrained on rails (the upper does nothing but cover the moving parts, and hold the charging handle & sights). New TP9 upper, and I have a 600$ SPP you can actually mount sights on

The Remington R51 has a separate breech block, probably the most 'common' modern design with the feature that operates on its own recoil (DE is gas operated, therefore you would expect it to have a separate breech block). Where those guns made properly, they would have a number of distinct advantages over short recoil designs, but don't really stem from the breech block being enclosed, per se (more to do with it being stationary then lifted & dragged back halfway through the cycle, these different steps redirecting bolt recoil downward & slowing the slide down before it impacts the stop, resulting in a smoother/lighter recoil impulse overall. Short recoil actions have no stationary breech parts prior to unlocking)

In a recoil operated system, mass is everything. It's very much like a blowback design in this respect, only operating at higher power levels. Modern cartridges can push even the mitigating features of the locked breech recoil operated design to its limits as far as slide velocity, so the mass of the reciprocating parts is once again the limiting factor. By enclosing this inside a stationary shroud (Steyr SPP) all you do is make your mass/volume more inefficient, in a design field where weight/size efficiency is more important than almost anything else. It's also unnecessary, since a monolithic slide with internal hammer or striker will not hinder or impact anything not directly in front of or behind it (external moving parts were seen as a point of failure early on, as compared with revolvers, but history has shown it to be largely a non-issue)

The reason the slide has become integral to the bolt over time, rather than the barrel as it was initially, is because of modern production improvements and a greater understanding of the needs of the short recoil process. We now know that having a greater portion of your moving mass in play after the action unlocks, means more assertive extraction/ejection. We also know it is far cheaper to produce a milled slide and rifled barrel separately (I don't know for sure, but I suspect it may have been cheaper or more practical back in the day to have both these critical elements combined into a single part, when more manual labor was involved)

"Closed bolt" is a misnomer for what you are describing, from what I can tell. I think you mean "locked breach," and the subcategory with an "enclosed action." Open bolt guns fire when the bolt or bolt carrier assembly reach full forward travel, usually with a fixed firing pin and blowback action for pistol calibers, and are (over)broadly classified as machine guns.

TCB

[barnbwt]

Both unnecessarily complicated, both are unnecessarily expensive.

The PX4 is literally no more complicated than a hammer fired Browning-offspring like a SIG. The fancy machining that rotates the barrel isn't actually all that complicated, and is at any rate just as expensive as a tilting barrel/cam & pin with modern CNC tooling options. The Stoeger Cougar is the same thing made overseas, and was like 350$ until fairly recently. The Berettas are expensive for the same reason all Berettas are expensive

TCB