Why does the blowback action stop at 380

J

johnm1

New member
If you ever wondered why the straight blowback action generally stops at 380, below is the picture why. This is the bolt from a Winchester 1907 semi auto rifle in 351WSL. It is a straight blowback design. Yes, it is a rifle. But it demonstrates the weight and size of the bolt required to withstand the higher pressures. The 351WSL is approximately the equivalent of a 357 magnum, maybe a little more. It propels a 180 grain projectile at close to 1900 FPS out of a 20 inch barrel. The coins are for scale. The bolt assembly weighs approximately 2 1/2 pounds. The spring that operates it is quite stiff.

Winchester made the 1910 in .401 WSL that propelled a 200 grain projectile at over 2000 FPS. Probably not going to put that in a hand gun.

So, what Hi Point did was actually a bit elegant considering the obstacles that have to be overcome. (Can you use Hi Point and elegant in the same sentence:confused:?). And there are exceptions. I have an Astra 600 in 9mm Parrabellum that is a straight blowback that seems to work just fine. Not for the 'Dainty' but functional.
 

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Blowback

I think you have answered your own question weight and spring tension. Even with modern polymers a handgun would probably weigh well over 3 lbs. and the leverage to over come the springs would require a very long barrel or an out sized bolt handle. It could be done but the pistol might look more like a cut down A-5 than a conventional design.
My two cents.
 
George, it appears that John was offering an explanation, not asking a question.

Thanks to PCCs, many people are learning, and some not in a good manner, the limitations of blowbacks. You could not give me a .40, or 10mm in a blowback.
Mass, springs, hydraulics, backbored barrels are all being tried to keep cases from blowing out, extractors from popping, etc. At least in the 9mm PCCs, lighter bullets and faster powders do help, but to some that seems counter-intuitive. But guns are not designed on intuition. :eek:
 
Blow back center fire pistol caliber rifles seem to work good.
At least the few I've tried.
No complaints.
Probably slower actions that other designs, so maybe not as competitive in the new Pistol Caliber Carbine division, though.
But otherwise, plenty ok.
 
Mark was correct. I just thought others in the semi auto forum would like to see what I pulled out of this rifle as it relates to semi auto pistols. In the back of my mind I always thought a blowback in a larger caliber shouldn't be that hard. But the engineering to overcome the physics involved becomes more challenging. Almost st cartoonish.

The Astra 600 in 9 mm seems to address the function well. The slide is a bit stiff to pull back. But it is a military arm and to assume the user has enough strength to operate the action seems reasonable. I think the compromise in the design was in the disassembly of the arm. Very stiff and difficult to reassemble.
 
I appreciate the nuggets of firearms information folk toss out here from time to time. It's part of what keeps bringing me back here.

So thank you johnm1.
 
As I mentioned elsewhere, keeping the breech closed until the pressure drops to a safe level is the reason why most high power auto pistols are locked breech. The Astra pistols Models 400 and 600 get away with relatively light slides because the hammer strut is at a mechanical disadvantage, causing them to act as retarded blowbacks. When the Model 800 "Condor" was designed, the retarding feature was dropped to allow easier manual hammer cocking and the guns would not stand up to the 9mm P as well as the similar Model 600 did.

FWIW, most blowback semi-auto rifles that fire powerful cartridges have very heavy breechblocks. An example would be the old Winchester rifles in .35/.351/.401. They look like conventional rifles, but an examination shows that the breech block and its extension (inside the thin hollow foreend) are very heavy; the weight is not so noticeable in a rifle, though, so many shooters are less aware of the mass involved.

Jim
 
Cheapshooter: I'm trying to hit your link but just getting a general youtube page with trending youtube stuff on it...could be me and my computer though...
 
I don't know John, but I'm glad that we have locked actions for our more energetic pistol and rifle calibers. I kinda think there are practical considerations in using very heavy recoil springs and heavy slides/bolts. For instance, I suspect centerfire bottle neck cases are going to look like straight wall cases upon extraction from a blowback action. OK I guess if one never intends to reload those cases, like military,etc. While it would be a lot easier and cheaper to make centerfire blowback pistols and rifle actions, I notice that the vast majority of designers of military and commercial firearms take the more difficult, and expensive, route to design strong locked actions. I think some of my favorite pistols, 1911s, FN/Browning Hi Powers, SIG P210s, etc. would look a lot more like High Points if designed as blow backs. Now that's a disturbing mental image;)

In fairness, I do like my little Marlin Camp 9, with blowback action (14 Oz. bolt) and heavy recoil spring. But I consider it just a light duty plinker and do not consider it a serious, heavy duty pistol caliber carbine at all. If I needed, or had a serious desire, for a more robust 9MM carbine, I'd invest in a locked bolt type like the SIG MPX,etc.
 
DaleA Might be the way I posted it trying to save people from a bunch of useless advertising LOL
Just google iraqveteran8888 10MM Hi-Point.
 
The "Official Explanation" is that above 380 ACP you either need a recoil spring that is so powerful that 98% of us mortals couldn't draw the slide back or a breech block that is so heavy that the pistol would weigh 5-6 pounds.
 
I think the take away from the discussion is that we often wonder 'Why did they design it that way'? The physical limitations are sometimes much greater than we as end users think they ought to be. Let's face it. I'm not an engineer/designer.

The next thing that designers have to deal with are existing patents. John M. Browning was a genius, yes. But one of the 'Genius' aspects might well have been patenting some pretty simple things. Like the breach block attached to the slide or, get this, using a screw to attach grip panels. That one was pure genius. My point is that some designs, even the entire of concept of how to keep the breach closed were not always chosen because that was the simplest/easiest way to accomplish the task. Sometimes the designers had to figure a way to 'design around' other's patents. The semi-auto pistols that come to mind are the Remington Model 51 and the Savage 1907. There is a beauty to each of those designs but both are complicated when compared to JMB's design. But if you can't use a tilting barrel you have to devise another way to keep the breach closed long enough for pressures to reacg a safe level.

We have some really wonderful designs out there that address different problems 'Elegantly'. And elegant can mean a lot of things depending on what the problem your trying to solve is. Not to support or poo poo the High points. This is just an example of a problem that engineers are sometimes faced with. If your mandate is to produce a serviceable semi-auto handgun at a price point of $200 that almost demands a straight blowback action. I can't think of any of the delayed or locked breach methods that don't involve a lot of fitted parts. One could argue that a price point of $200 is unwise. But there is a market for it. I believe the counter guy at the LGS (OK so there might be a chink in my armor) and they report that more Hi Points walk out the door than any other brand. And they make as much on a Hi Point as any other brand. Reality is the LGS's don't make a lot on new hand guns no matter the price point.

I've been rambling on here, but I wanted to make sure this post got back to semi-auto hand guns and not the rifle. And for us to think about the designs of our hand guns and what problem was the designer was trying to address.

One last reference to the original bolt/bolt extension from the OP and the rifle it is in. The bolt/bolt extension photographed in the original post was from a Winchester Model 1907 in 351 WSL. This was a direct competitor to the Remington Model 8. Both could have been designed as gas operated but weren't. The technology existed in the Standard Model G from the turn of the century. But both designers elected to use a different method of keeping the breach closed. Both used a heavy weight. In the case of the Model 8, the weight of the barrel is included even though that breach is locked. I don't know if the designers were both trying to avoid a patent from the Standard Model G or if they were just convinced that their design was better. It was early in the design history of firearms. Who knew? But the Model 8 is pretty complicated while the 1907, although pretty simple, is really reaching the edge as far as what the technology could support.

Food for thought. I hope I got the facts right (or at least close) and this leads to a decent discussion. There are some really knowledgeable people here who know a lot more than I.
 
I've long been a fan of the delayed blowback .It's been with us for over 100 years and some fine guns are included though the Savage I wouldn't include as the delay is hardly enough. The Rem 51 I had was a fine gun and that got me started. Then I was introduced to H&K in the form of the wonderful P7 ! Incredibly reliable for various reasons ,the PSP and M10 are staying with me ! They of course also had rifles .:D
 
Hi, Johnm1,

The Winchester Model 1905 came out in 1905* but the patent dated to 1900; the Standard Model G came out in 1909/1910. so it was after the Winchester, not before.

*The Model 1905 was in .35 Winchester (not to be confused with .35 Remington, a much more powerful round). The Model 1907 was basically the same as the Model 1905, but beefed up to handle the .351 Winchester. It was the "cop rifle" for many years, often used along with, or in lieu of, the later less powerful, but "sexier", Thompson SMG.

Jim
 
One note on blowback rifles. I have read that a blowback rifle in .30-'06 would have to have a 28 pound breechblock, so anyone thinking of a light sporter....

Jim
 
johnm1 said:
The next thing that designers have to deal with are existing patents. John M. Browning was a genius, yes. But one of the 'Genius' aspects might well have been patenting some pretty simple things. Like the breach block attached to the slide or, get this, using a screw to attach grip panels. That one was pure genius. My point is that some designs, even the entire of concept of how to keep the breach closed were not always chosen because that was the simplest/easiest way to accomplish the task. Sometimes the designers had to figure a way to 'design around' other's patents. The semi-auto pistols that come to mind are the Remington Model 51 and the Savage 1907. There is a beauty to each of those designs but both are complicated when compared to JMB's design. But if you can't use a tilting barrel you have to devise another way to keep the breach closed long enough for pressures to reacg a safe level.
Click to expand...
But you can work around patents. One of the things that made John M. Browning a genius was that he was smart enough to engineer around his own patents.

The M1911 used a tilting barrel, with a swinging link attached to the underside of the barrel to achieve lock-up and link-down. JMB sold that patent to Colt. So when FN hired him to design what was to become the Hi-Power, he wanted to use the locked breech design but he couldn't use the swinging link. So ... he put a cam-shaped slot in the barrel's underlug. It accomplishes the same thing, with fewer parts, and didn't infringe on the previous patent.

Genius.
 
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