straight blowback 9mm

S

simonrichter

New member
just a thought: In order to make a 9mm (or even more powerful caliber) in a straight blowback design, you need a strong recoil spring and a relatively heavy slide (like the HighPoint models).

I take it that there is a limit to the strength of the recoil spring since you have to rack the slide in order to operate the gun, which becomes impossible with a overly strong spring.

Would it be, theoretically spoken, possible, to use a extremely strong recoil spring that makes an extra-heavy slide unnecessary and use the tip-up-barrel-system that is now only used for some mouse guns for chambering the first round?
 
I suspect the inertia of a heavy slide is necessary, since the weight of the spring increases as it's compressed

I imagine any spring string enough to keep the action closed long enough would restrict the travel distance too much
 
Research the HK VP-70 . The trick was to make rifling grooves twice as deep as usual ---dropping the velocity a significant amount !
Another pistol was the Spanish [forgotten the name at the moment ] one that took a bit of stregth to operate.
Both weren't successful in solving the problem.
 
mete said:
Another pistol was the Spanish [forgotten the name at the moment ] one that took a bit of stregth to operate.
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You're probably referring to the Astra 600.

The slightly larger but otherwise similar Astra 400 is meant to fire the longer 9x23mm Largo aka 9mm Bergmann-Bayard cartridge; however, some individual pistols will feed and fire 9x19mm Luger with reasonable reliability, but the shorter cartridge headspaces off the extractor and the wisdom of this practice is disputed.

FWIW Astra later made a variety of modern 9mm pistols such as the A-70 and A-80 that use conventional tilting-barrel locked-breech operation.
 
Both weren't successful in solving the problem.
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I have fired the Astra, a fully functional 9mm Luger blowback. The slide is not impossible to operate, maybe a 20lb pull, stiff, but not unworkable for a normal adult.

The feel of the recoil was surprisingly heavy, seemed to be more than a locked breech semi of similar size., but that's just my opinion of the feel, I didn't do a side by side comparison. The other noticeable thing was that it was much louder than any other 9mm I had shot.

Research the HK VP-70 . The trick was to make rifling grooves twice as deep as usual ---dropping the velocity a significant amount !
Click to expand...

As I recall, the VP-70 had polygonal rifling, which was claimed to give it a velocity increase.

One could build a gun like you describe, light slide /bolt and uber heavy spring. Using the tip up barrel to load the first round would also work.

Now, what do you do if you have a stoppage or feed issue where you have to pull back the slide? Tipping up the barrel only lets you get at the chamber. If you have a problem with a round coming out of the mag, or stovepiped, you have to pull back the slide, some, at least. TOO strong a spring would make that a tough job.

Its a balancing act, spring tension, bolt mass, and the thrust from the firing round. There are equations to work out what is needed if you change one of these variables.
 
Would it be, theoretically spoken, possible, to use a extremely strong recoil spring that makes an extra-heavy slide unnecessary and use the tip-up-barrel-system that is now only used for some mouse guns for chambering the first round?
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This was the principle used on the Smith & Wesson .35 (and later .32 auto) pistols, which, in turn, were based on the earlier Belgian Clement patents.

The recoil spring was so stiff that a means to disconnect the extremely light recoiling bolt from the recoil spring was necessary to be able to cock and load the pistol.

While they are extremely well-made pistols, they were not a rousing success.

Do a little Google search for more info on the .35 and .32 S&W autos.
 
The Steyr GB is a gas-delayed blowback, which when fired next to a "modern" design has a significantly-sharper recoil impulse. But Wikipedia claims the systems delivers 30% more power. I have no way to verify or deny. I happen to like mine immensely, but there are easier to live with designs out there now. The GB is a stone-cold project to clean. Carbon gets blown all over the innards of that beast.

http://en.m.wikipedia.org/wiki/Steyr_GB
 
Would it be, theoretically spoken, possible, to use a extremely strong recoil spring that makes an extra-heavy slide unnecessary
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Not practically possible. The spring rate cannot be heavy enough to delay the breach from opening and still be practical for most people to operate. The spring is really only there to "catch" the slide so it doesn't batter the frame, and of course to re chamber the next round.

Proper breach opening delay relies heavily on slide mass.
 
simonrichter said:
Would it be, theoretically spoken, possible, to use a extremely strong recoil spring that makes an extra-heavy slide unnecessary and use the tip-up-barrel-system that is now only used for some mouse guns for chambering the first round?
gyvel said:
This was the principle used on the Smith & Wesson .35 (and later .32 auto) pistols...
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Click to expand...
Kinda. The S&W pistols' barrel doesn't tip forward for breech-loading; it tips up from the top rear, and this feature is meant primarily for cleaning. (Gyvel, I bet that you know this and you simply didn't explain it adequately, so pardon me for jumping in. :))

The barrel is attached to a long extension that attaches to a riser at the rear of the frame. The bolt fully encircles the frame riser, thus making it impossible for the bolt to fly off the gun on firing. It seems like a pretty clever idea until the designer realizes that the necessarily hollow and therefore low-mass bolt mandates a really stiff recoil spring. This had not been a big problem with Clement pistols because they were usually chambered in a special (puny) 5mm Clement cartridge or in (slightly less puny) .25 ACP.

S&W attempted to work around this problem with the recoil spring disconnect latch, which fits in the category of Nifty Mechanisms Invented to Mitigate Inherent Self-Imposed Design Flaws, kinda like balance shafts on 90-degree V-6 engines. :rolleyes: The second attempt to address the problem was low-power ammunition; the .35 S&W cartridge was loaded significantly below .32 ACP power levels, around 105-110 FPE at the muzzle.

Has it been mentioned that the intricate design led to high production costs and a consequent high MSRP?

Buyers ignored the pistol in droves. Subsequent beefing-up of the bolt to allow the use of commonplace and non-proprietary .32 ACP ammo didn't help much. Clement-type autos have proven to be an evolutionary dead end.
 
"Would it be, theoretically spoken, possible, to use a extremely strong recoil spring that makes an extra-heavy slide unnecessary and use the tip-up-barrel-system that is now only used for some mouse guns for chambering the first round?"
Doubtful. The bolt thrust of any centerfire cartridge is in the thousands of pounds; adding even 100lbs of spring resistance to the bolt in battery won't do much to keep a cartridge from blowing out too soon. What the stiff spring could do, is stop/return the bolt with a reduced impact upon the slide or bolt stops. However, 9mm's momentum is so low that I suspect a heavy spring would bounce a light bolt back before it could even retract enough to eject & feed. There is a similar problem for really heavy bolts with light springs, but due to friction losses.

"a simple and light design with a fixed barrel."
Look into the Pedersen Hesitation Lock. Though sullied by Remington's R51 execution, it was an outstanding 32/380 (and allegedly 45acp) design that was nearly as simple as blowback and retained all its advantages, but as strong as a full-on locked breech so long as a cartridge with a sufficiently thick case head (most of them) was used.

TCB
 
^^^ Another example is the lever-delayed blowback system used in the Benelli B76 and B80. It's a nifty system; the pistols themselves were a marketing failure, but this is generally attributed to other factors.
 
Of course it is possible, but you always have to remember that the stiffer the spring gets, the less user friendly the pistol will be. There are a few light and compact pistols out there. Have you seen the diamondback 9mm? It handles really well and is not too heavy or hard to cock.
 
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