The discussion in the thread titled 'Compact/Full Sized .380s w/locked breech' confirms the general understanding that locked breach actions are softer shooting than straight blowback. But why? In my straight line thinking the locked breach should transfer all of the force to the hand while the blowback would have some 'give' to it. I realize that the blowback stays closed until the pressure builds and has enough force to move the bolt backwards but at best, again in my straight line thinking, the two would be at least equal in delivering the same force to the hand during the lock period. Is it the mass of the blowback bolt after the initial lock that makes the recoil felt greater?
Why are Locked Breach 'Softer Shooting' than a Blow Back Action?
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edwardware
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Yes, but no. Mechanically delayed blowback actions sometimes feel softer because the kinematics of unlocking spread the recoil impulse out in time. Mass delayed blowback actions with reasonable bolt mass and spring weight tend not to.
No. The pressure is orders greater than enough to move the bolt almost instantly after the primer goes. The mass of the bolt takes time to accelerate, hence mass delayed blowback. The bolt moves very little before the bullet's gone, but by that time the momentum is stored in the bolt, and it carries on it's merry way back.
.380ACP is about the largest cartridge that can be handled with reasonable bolt mass and spring weight, but there's no physical limit. The Grease Gun is a mass delayed blowback action, but the bolt is a large steel brick to provide enough delay.
The angle of the impulse doesn't matter much, especially compared to the moment created by bore height above your grip.
tark
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You are aware of the Astra 400/600 series pistols that fire 9X19 and 9X23 (Largo) I assume. They are "mass blowback" inertia locked pistols, firing cartridges that are quite a but more powerful than the .380. Some of the Largo military ammo (NOT subgun ammo) came in at just over 1200 FPS with a 128 gr bullet. High Point does make a 45 ACP blowback operated pistol, but it feels top heavy and awkward because of that very heavy slide,
These three cartridges are pretty close to the limit for a reasonably sized (as in weight ) pistol.
At work have you ever had to explain a relatively simple, to you, concept to a co-worker and you get that 'I don't get it' look like you just explained it in Mandarin Chinese. I hear what you're saying, but at this point I still don't 'understand' it. I'm sure its not what you are saying or even how you are saying it. It's my brain that can't yet put together what is happening that makes it feel different.
I'm an engineer for a construction company. That's a title not a degree. But I do have a NY State Regents diploma in Music, Math, and Science and two years of engineering classes including several physics and calculus classes that I passed. So I have a pretty good understanding of Newtonian physics. Or at least I think I do. Maybe when we are done here I'll have to change that assessment of myself.
I figured that the mechanically delayed blowback spread the impulse over a different time period and that accounted for the difference in what is felt by the shooter. I just don't understand how it does that. My initial assumption was that the mechanically delayed action Produced 100% of the initial recoil because the firearm stayed 100% in battery for the entire time until released from battery. While in the blowback action the bolt started to move immediately but stayed 'closed enough' to perform its function and that little bit of movement would reduce the initial recoil impulse. Thinking about this a bit more and reading the above response there is now an assumption on my part that the amount of time the firearm remains in battery is the same or very similar in both the mechanically locked and blowback actions. That may be a bad assumption on my part.
Blow back actions tend to have heavy bolts and I assume that when the heavier bolt hits the end of its rearward travel it hits 'harder' because it is heavier. F=Mass x Acceleration. But I just can't get over that each system, either mechanically delayed or delayed by mass/spring, the bolt either hasn't moved (in the case of the mechanically delayed opening) or hasn't move much (delayed by the mass of the bolt and the spring) initially. So shouldn't the initial felt recoil be almost exactly the same? And if the bolt on the blowback action has moved even a little bit in the same time period that would have transferred some of the initial forces to the bolt movement reducing the amount of initial felt recoil. That force only coming back into play when the heavy bolt stops at the end of its rearward travel.
Is the initial felt recoil from the 'in battery' condition just not what makes the recoil feel 'sharper'? Is it just the fact that the blowback actions bolt is heavier and hitting harder that causes the 'sharper' recoil on the blowback? That would relieve my confusion and maybe settle the whole question.
NOTE: I'm not saying that anything above is the way it is, but it is the way my brain interprets it. My 'Paradigm' if you will.
Maybe the better question is what part of the recoil cycle gives the shooter the 'sharper' recoil impulse? The initial point while both actions are in battery, the travel of the slide rearwards, the transition from rearward slide motion to a stop and then to a forward slide motion or when the forward motion of the slide stops? (my 6th grade English teacher would have belittled me for that run on sentence! Please don't hit my Mrs. Zazaretti)
What would be great is if a manufacturer made a single pistol in both delayed and straight blowback actions. Then we could actually measure the differences. But I don't suppose one of those exists. The closest that comes to mind is the Llama mini-1911 types of pistols in 380. They made them in both delayed and straight blowback. And I'd suspect they were very close in how they were constructed except for the mass of the slide almost had to be increased to slow the opening from battery. But maybe the slide was heavy enough and all they had to do was replace the delayed action parts with a fixed barrel. Technical writing takes time and effort and I'm not sure I wrote things in a manner that could be understood. Hope I haven't lost anyone on this topic.
ontarget
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I have always kind of assumed that the difference in the weight of the moving parts was what made the recoil impulse feel different between the two systems.
entropy
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It does. The angle of the impulse in a long gun most certainly does affect felt recoil. Also while not affecting felt recoil as much in a pistol, it does affect muzzle flip, as does barrel length.
The rest of your post is exactly right.
delayed blowback also allows the barrel to move, and turns the muzzle up a bit, the locking block alters the torque or angle of force as well. the combination of all these thing happening in a direction that is not directly back - certainly reduces felt recoil.
I think I have over thought this. Like I've never heard my wife say that. I've had it in my mind that it is the method of how the firearm locks into battery that causes the amount of felt rcoil when I think it is simply the mass of the blowback action is the cause like @ontarget posted. Preconceived ideas are hard to overcome.
chicharrones
needs more ammo
Maybe I missed this being brought up, but here's my thought from hands on time with blowback, short recoil, locked breech, etc.
One thing to be considered is that the lighter the slide on a pistol, with a given cartridge, the heavier the recoil spring (and possibly hammer spring) seem to be.
When I cycle the slide in blowback guns, the slide is almost always harder to cycle manually than when compared to a comparably sized non blowback gun. Which is telling me the recoil (and hammer) spring are likely not as stiff in the non blowback gun.
Makes me think the hand is taking the brunt of the spring compression action when firing and this is felt more in a blowback gun due to a stiffer recoil spring. Which would also explain why I believe it is easier to limp wrist a small blowback autoloader than a non blowback gun in the same size.
Plus, blowback gun slides do feel like they pound your hand more when the slide hits full retraction. Likely why many blowback actions, mostly carbines, have internal buffers to prevent the gun from pounding itself.
In my experience with any gun, if the slide weight is increased and the recoil spring is lightened, the sharpness of the felt recoil is lessened.
But increasing the slide weight will make a blowback pistol heavier or bulkier, so in goes the stronger recoil spring.
One thing to be considered is that the lighter the slide on a pistol, with a given cartridge, the heavier the recoil spring (and possibly hammer spring) seem to be.
When I cycle the slide in blowback guns, the slide is almost always harder to cycle manually than when compared to a comparably sized non blowback gun. Which is telling me the recoil (and hammer) spring are likely not as stiff in the non blowback gun.
Makes me think the hand is taking the brunt of the spring compression action when firing and this is felt more in a blowback gun due to a stiffer recoil spring. Which would also explain why I believe it is easier to limp wrist a small blowback autoloader than a non blowback gun in the same size.
Plus, blowback gun slides do feel like they pound your hand more when the slide hits full retraction. Likely why many blowback actions, mostly carbines, have internal buffers to prevent the gun from pounding itself.
In my experience with any gun, if the slide weight is increased and the recoil spring is lightened, the sharpness of the felt recoil is lessened.
But increasing the slide weight will make a blowback pistol heavier or bulkier, so in goes the stronger recoil spring.
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barnetmill
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In a typical delayed blow back gun, the barrel is fixed and does not move. You might be confusing the roller locked short recoil CZ 52 with delayed blow back.
In a blow back gun that functions strictly on inertia for locking, the major component of recoil is at the end of the rearward movement when the slide stops for a pistol.
This is a guess on my part: A typical short recoil system like a 1911 seems to have two points for when the shooter 'feels' recoil forces. One when the barrel unlocks and the last when the slide is stopped at the end of its recoil.
chicharrones
needs more ammo
Speaking of slide weights, I can think of two blowback guns that were first produced with a given slide weight which was increased in later models.
The Beretta 81 to 81BB and the Beretta Tomcat. The word was that the Tomcats slide was widened and made heavier due to the preceding lighter slide slamming (accelerating?) into the frame hard enough to crack that frame. I'm not sure why the 81BB slide was widened, but maybe to ensure the same wouldn't happen even though the 81 predates the Tomcat.
I don't know if recoil springs changed in these guns without looking up part numbers, but it is an indicator how hard a slide impacts the frame while cycling in blowback guns.
The Beretta 81 to 81BB and the Beretta Tomcat. The word was that the Tomcats slide was widened and made heavier due to the preceding lighter slide slamming (accelerating?) into the frame hard enough to crack that frame. I'm not sure why the 81BB slide was widened, but maybe to ensure the same wouldn't happen even though the 81 predates the Tomcat.
I don't know if recoil springs changed in these guns without looking up part numbers, but it is an indicator how hard a slide impacts the frame while cycling in blowback guns.
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chicharrones
needs more ammo
Here's a little comparison between my blowback CZ82 and non blowback CZ75D PCR.
Both are nearly the same physical size with virtually identical grip widths and feel in the hand.
The CZ82 in 9 Makarov weighs 27.7 ounces empty and its slide weighs 9.2 ounces.
The PCR in 9 Parabellum weighs 26.6 ounces empty and its slide weighs 10.7 ounces.
In my hands, the CZ82 has sharper felt recoil even though it is firing a weaker cartridge and is similarly sized and weighted.
Both are nearly the same physical size with virtually identical grip widths and feel in the hand.
The CZ82 in 9 Makarov weighs 27.7 ounces empty and its slide weighs 9.2 ounces.
The PCR in 9 Parabellum weighs 26.6 ounces empty and its slide weighs 10.7 ounces.
In my hands, the CZ82 has sharper felt recoil even though it is firing a weaker cartridge and is similarly sized and weighted.
1942bull
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Going back in thinking to physics class in high school my thoughts are all based upon the fact that every action of force has an equal and opposite reaction. That it what recoil is. Blowback recoil travels straight back and the opposite force is stopped buy the end of travel of the slide. With locked breach as the barrel tilts tilts the reaction force is partially directed on a downward angle while at the same time partially traveling rearward. That splitting of the reaction force means lass impact at the end of slide travel. Maybe we have a physics expert onboard who can explain it better. If there is I hope we can see a mathematical calculation of the forces of both designs.
barnetmill
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This has been an enlightening thread. Thanks for all of the comments so far.
Here’s an off the wall thought. I think my company owns a field accelerometer. Or at least we did. Is there anyone with a straight blowback Llama Micro Max or similar model in Arizona close to Phoenix? Not sure we could develop a reasonable test to compare them to each other. But we might. I don’t have a laboratory but we might be able to fix test guns to an anchored vice to remove movement from the equation. First off would be to compare weights of the relative parts to see if the comparison would even make sense. The assumption being that the blowback design had to increase the mass of the slide when the design went from delayed to straight blowback. Maybe they only increased the spring strength. Not sure how to measure that. But that seems at least as likely as increasing the mass of the slide. Possibly both.
Yep, probably never happen. It it’d be interesting.
Here’s an off the wall thought. I think my company owns a field accelerometer. Or at least we did. Is there anyone with a straight blowback Llama Micro Max or similar model in Arizona close to Phoenix? Not sure we could develop a reasonable test to compare them to each other. But we might. I don’t have a laboratory but we might be able to fix test guns to an anchored vice to remove movement from the equation. First off would be to compare weights of the relative parts to see if the comparison would even make sense. The assumption being that the blowback design had to increase the mass of the slide when the design went from delayed to straight blowback. Maybe they only increased the spring strength. Not sure how to measure that. But that seems at least as likely as increasing the mass of the slide. Possibly both.
Yep, probably never happen. It it’d be interesting.
wiscoaster
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Rapidly scanning posts I may have missed it if already mentioned: but felt recoil depends to a large extent on the frame. Just saying a blowback action produces more felt recoil is a very broad brush. Taking all the physics into account, it's the frame that imparts the felt recoil to the shooter and so the mass of the frame has a lot to do with that; also frame design, material, bore axis, grip angle, etc etc. I've got a number of blow back action pistols and I can't say that in general all their felt recoil is attrocious. As a matter of fact in general, I'd probably say the steel-framed items aren't bad at all. It's the ones with the polymer frames that are the snappiest.
Another thing that I don't see mentioned is the snap when the slide hits the end of its travel. Yes, with a perfect balance of energy, spring, and slide weight, such a thing would never happen, but we all know that it is unlikely to ever work that way.
In order to answer the question if the blowback action imparts more recoil than another type of action we would need the same model of gun manufactured in both type of action. Locked and blowback. I don’t Imagine many manufacturers made them both ways. The exception being the Llama mentioned above. Llama took the delayed model and turned it into a fixed barrel straight blowback. I assume for cost reasons. That would be as close as one could come unless someone knows of another brand/model that changed from delayed to blowback.
Mosin77
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I’m no physics major, but, in a few sentences:
The straight blowback has no resistance except whatever the strength of the spring or the mass of the slide can provide. So all of the equal and opposite reaction to the bullet’s being propelled down the barrel, goes into throwing back that slide rather violently. The only thing that keeps this “safe” is that the cartridges are relatively weak enough that by the time the breech opens to allow gases to escape, the bullet has exited the barrel and pressure has dropped to a safe level. The slide and spring together, alone, provide enough resistance to the relatively-weak cartridge’s ignition, to delay breech opening long enough, for pressures to be safe. You feel the violent straight-backwards force of the slide hurtling backwards, slamming into the stop, and the whole gun then being propelled into your hand.
The locked breech mitigates this, and allows for more powerful cartridges, by keeping the breech locked during part of the recoil, to give the pressure in the breech a few more milliseconds to drop to a safe level. During that few milliseconds the energy from our equal and opposite reaction is being used to unlock the breech, whether that involves tilting the barrel, rotating the barrel, or some other system. After the breech is mechanically unlocked the action becomes “blowback” and the slide is thrown backwards to its stop. But by the time this occurs, some of the energy has been spent to unlock the breech, so slide movement is not as violent as it would be if the same cartridge and slide were used with a straight blowback action. The locked breech requires more machining, more parts, more expertise to make, and so historically was not used if it was judged that a blowback could do the job as well from a functional point of view. But straight blowbacks are essentially a balancing act between the weight of the slide, weight of the spring, and power of the cartridge. You can have a monster 9mm blowback but it will need a monster spring (Astra) or monster slide (Hi Point). The most powerful cartridges usually found in a blowback (reasonably light/normal slide, stiff but not excessive spring strength) are 9x18 Makarov or .380 acp. A .380 locked breech will be both easier to rack (not as strong a spring necessary) and have less felt recoil, since the energy is dissipated over a slightly longer length of time, and is used to perform actions which are not necessarily straight backwards into the hand.
Another advantage of blowback pistols, beyond manufacture cost, is their fixed barrel. They can be noticeably more accurate.
Because most people can handle the recoil of a .32 in blowback, almost no pistols have been made in .32 with a locked breech. But .380s are becoming more common because they’re often, nowadays, designs recycled from 9mm and marketed specifically for the recoil averse.
The straight blowback has no resistance except whatever the strength of the spring or the mass of the slide can provide. So all of the equal and opposite reaction to the bullet’s being propelled down the barrel, goes into throwing back that slide rather violently. The only thing that keeps this “safe” is that the cartridges are relatively weak enough that by the time the breech opens to allow gases to escape, the bullet has exited the barrel and pressure has dropped to a safe level. The slide and spring together, alone, provide enough resistance to the relatively-weak cartridge’s ignition, to delay breech opening long enough, for pressures to be safe. You feel the violent straight-backwards force of the slide hurtling backwards, slamming into the stop, and the whole gun then being propelled into your hand.
The locked breech mitigates this, and allows for more powerful cartridges, by keeping the breech locked during part of the recoil, to give the pressure in the breech a few more milliseconds to drop to a safe level. During that few milliseconds the energy from our equal and opposite reaction is being used to unlock the breech, whether that involves tilting the barrel, rotating the barrel, or some other system. After the breech is mechanically unlocked the action becomes “blowback” and the slide is thrown backwards to its stop. But by the time this occurs, some of the energy has been spent to unlock the breech, so slide movement is not as violent as it would be if the same cartridge and slide were used with a straight blowback action. The locked breech requires more machining, more parts, more expertise to make, and so historically was not used if it was judged that a blowback could do the job as well from a functional point of view. But straight blowbacks are essentially a balancing act between the weight of the slide, weight of the spring, and power of the cartridge. You can have a monster 9mm blowback but it will need a monster spring (Astra) or monster slide (Hi Point). The most powerful cartridges usually found in a blowback (reasonably light/normal slide, stiff but not excessive spring strength) are 9x18 Makarov or .380 acp. A .380 locked breech will be both easier to rack (not as strong a spring necessary) and have less felt recoil, since the energy is dissipated over a slightly longer length of time, and is used to perform actions which are not necessarily straight backwards into the hand.
Another advantage of blowback pistols, beyond manufacture cost, is their fixed barrel. They can be noticeably more accurate.
Because most people can handle the recoil of a .32 in blowback, almost no pistols have been made in .32 with a locked breech. But .380s are becoming more common because they’re often, nowadays, designs recycled from 9mm and marketed specifically for the recoil averse.
chicharrones
needs more ammo
That's why I'm a fan of the few .32 ACP locked breech guns that are out there. Most folks know about the KelTec P32, and some know about the Taurus TCP732. My Taurus 732 is much softer shooting than my NAA Guardian blowback .32 ever was. If the Ruger LCP would have been introduced in the 1990s, for sure it would have been offered in .32 ACP.
chicharrones
needs more ammo
I definitely believe that can be the case in rimfire pistols such as a Ruger MK, Browning Buckmark, S&W 41, etc. where the sights are fixed to the barrel and/or frame.
Tallball
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To me, a blowback feels more like a push/snap straight backwards towards a spot near the back of the pistol.
A locked breech feels more like the whole pistol moves in my hand,
Blowback doesn't have to be painful. My heavy steel Makarov in 380 isn't unpleasant. My alloy-framed Beretta 84 has a wide grip that distributes the recoil nicely.
Some of my 32acp blowback pistols are an absolute joy to shoot: Colt 1903, Walther PP clone, Beretta 81.
Smaller lighter blowback pistols in 380 are pretty snappy... though it's not like little locked breech models like the LCP are gentle to shoot, either,
I have to be able to grip a small pistol so that I have good control of it, AND so that the slide won't bite me anywhere. If I can do that, I can probably shoot it okay, regardless if it's blowback or locked breech.
pleasant to shoot (locked breech)
also pleasant to shoot (blowback)
A locked breech feels more like the whole pistol moves in my hand,
Blowback doesn't have to be painful. My heavy steel Makarov in 380 isn't unpleasant. My alloy-framed Beretta 84 has a wide grip that distributes the recoil nicely.
Some of my 32acp blowback pistols are an absolute joy to shoot: Colt 1903, Walther PP clone, Beretta 81.
Smaller lighter blowback pistols in 380 are pretty snappy... though it's not like little locked breech models like the LCP are gentle to shoot, either,
I have to be able to grip a small pistol so that I have good control of it, AND so that the slide won't bite me anywhere. If I can do that, I can probably shoot it okay, regardless if it's blowback or locked breech.
pleasant to shoot (locked breech)
also pleasant to shoot (blowback)
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WestKentucky
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Combination of recoil direction and moving mass. Blowbacks are generally a linear recoil this all of the force is straight back parallel to the barrel. There’s a lot of moving mass there and when the mass hits the positive stops on the frame you feel that jolt as recoil. With a locked breach the recoil is generally a slightly different direction because things move around as the gun unlocks. Being that there is a mechanism that contains the pressure until the action opens there is less pressure on the slide and generally therefore a smaller slide moving around. There is less weight (energy) when the slide hits positive stops at the rear of its travel. It becomes the equivalent of which one thumps hardest when comparing a framing hammer and a maul. Blowback with the heavier slide is the maul.
tark
Member
My Astra 400 boarders on downright unpleasant to shoot. It pounds the web of your hand with every shot. I think the grip angle in relation to the bore axis is partially to blame. There is a lot of muzzle flip. My 600 is almost as bad.
Lucky Gunner has a pretty good video that addresses the comparison that, though not the subject of the video, concludes with his opinion that straight blowback feels snappier than a locked breach for the same reasons written in this thread by several posters. The video of the locked breach is very informative. I wish he had a similar video of the straight blowback but I assume it would appear similar except the barrel would not tilt.
I would pose that the amount of time the recoil is distributed is the same or very similar between the two types of action and that time is not a significant factor in felt recoil but the mass of the reciprocating parts is the difference. But I have no way of actually test and prove it.
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