GTA
All Springer/NP/PCP Air Gun Discussion General => Machine Shop Talk & AG Parts Machining => Engineering- Research & Development => Topic started by: rkr on March 30, 2016, 03:39:47 AM
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I've been wondering, why aren't there any commercial blowback semi-auto airguns? I was just looking at the Caselman drawings and the probe retreats about 35mm before venting out the pressure and that's all there is to make it semi-auto. It would be really quite easy to introduce similar semi-auto function to existing production guns, so why aren't there any? I do understand that Steyr 5 uses a more complicated version of the same thing but that Caselman design is so simple that it makes me wonder.
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Is the function of the old Crosman 600 semi-auto CO2 pistol anything like you are talking about?
https://support.crosman.com/hc/en-us/articles/203542900-600-Owner-s-Manual-EVP-1960-1970-
Someone mentioned to me that they had made a couple of guns that auto-cocked, and all he did was drill a very tiny bleed hole in the back of the valve. You still had to cycle the bolt by hand but you didn't have to mess with cocking the hammer. Like you say, there are parts and pieces of the system out there, but no one has put a total package together.
Lloyd
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No, I was talking about this design http://thehomegunsmith.com/CaselmanAPMG.shtml (http://thehomegunsmith.com/CaselmanAPMG.shtml)
The probe is just pushed back and it powers the whole loading event. The probe is ultra heavy and springs light but we should be able to fine tune it to better these days.
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I think for a serious system efficiency is the primary issue with blowback. There just isn't enough air pressure overhead to vent any pressure behind the pellet; the losses are unacceptable to most.
Tom
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I think for a serious system efficiency is the primary issue with blowback. There just isn't enough air pressure overhead to vent any pressure behind the pellet; the losses are unacceptable to most.
Tom
The problem may actually spring from probe diameter, there's much less force (area for the pressure to act against) in a .177 probe than there's in a .32 probe nose. With heavy masses and soft springs the air efficiency could be sorted so that the pellet/bullet has left the barrel before the probe vents out. Steyr uses a separate piston/hammer system that's powered from the airpath before the pellet, with large diameter piston (when compared to .177 probe nose) it seems to work fine. The good thing in these approaches when compared to shroud operated piston system is that there's no lead dust or debris to jam the system over time.
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although i dont have a link at the moment there is a gentlemen on the yellow that converts auto cocker paintball guns to 22 semi auto by milling a slot for the 22 MRod magazine , and a minor internal gas mod. As i recall his guns get 700 fps in 22, so the prohibitive nature of semi auto seems to be a mindset.. Especially in light of the huben design
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The FX Revolution uses a blowback system right?
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Akin to the SPYDER paintball markers .... BIG air hogs due to losses operating the blow back mechanics which not only recocked hammer but sequentially cycled bolt loading a fresh ball.
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very interesting , never held a revolution .I never knew why people generally disliked the electronic semis, there not complex at all but there seems to be be common theme; a delay in the shot kinda like "turbo lag" in car terms
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The FX Revolution uses a blowback system right?
No, Revolution uses air blast from the muzzle to cycle things. The bad thing in that approach is that lead dust and particles will enter the piping that transfers air. Another similar approach is FX Monsoon where there's a piston inside the shroud that operates the action.
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I think some definitions are necessary:
Blowback is defined as using chamber/barrel pressure to overcome the bolt closing spring force to cycle the action. Blowback systems have no battery locking mechanisms, they just overpower the spring that closes the action. This is why they are generally found only on 22lr and some very low power pistols like the 25 acp and the 9mm largo. These cartridges are not so powerful to overcome the bolt closing force prematurely but one that has enough residual gas pressure to operate the action. Blowback is the simplest of all autoloader designs.
A system that uses a gas pressure to push piston that unlocks the bolt, then uses residual gas pressure in the barrel to cycle is referred to as Gas Operated.
A system that uses the inertia of a sliding barrel or other action component to unlock the bolt, then uses residual gas pressure in the barrel to cycle the action is referred to as Recoil Operated
There are a few systems that use a gas powered piston as a slave to cycle the bolt without residual gas pressure from the barrel, these are generally considered Gas Operated too.
The FX and Huben are not Blowback designs. There simply is no extra gas to loose in an Airgun for a blowback system. My opinion of course.
Tom
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I think some definitions are necessary:
Blowback is defined as using chamber/barrel pressure to overcome the bolt closing spring force to cycle the action. Blowback systems have no battery locking mechanisms, they just overpower the spring that closes the action. This is why they are generally found only on 22lr and some very low power pistols like the 25 acp and the 9mm largo. These cartridges are not so powerful to overcome the bolt closing force prematurely but one that has enough residual gas pressure to operate the action. Blowback is the simplest of all autoloader designs.
A system that uses a gas pressure to push piston that unlocks the bolt, then uses residual gas pressure in the barrel to cycle is referred to as Gas Operated.
A system that uses the inertia of a sliding barrel or other action component to unlock the bolt, then uses residual gas pressure in the barrel to cycle the action is referred to as Recoil Operated
There are a few systems that use a gas powered piston as a slave to cycle the bolt without residual gas pressure from the barrel, these are generally considered Gas Operated too.
The FX and Huben are not Blowback designs. There simply is no extra gas to loose in an Airgun for a blowback system. My opinion of course.
Tom
The Caselman is the only blowback airgun design that I know of, that's the reason for this post originally. I actually do have a .22 semi auto project that I will try in blowback mode someday to see if it would work in small bores, I doubt it has enough power to push the probe and hammer back but it's worth giving it a go. I believe the most succesfull semi auto airgun is the steyr hunting 5, I guess it would be gas operated in your categorization. As far as electric versions go the problem is most often reliability, to move the probe a gear system is usually employed and those things are prone to jam. A solenoid system + no probe magazine (like Steyr has) would probably be fine. Hmm, a separate solenoid could operate the probe as well if it comes to that.
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rkr, does the Steyr auto index the magazine or is it manual? Not any around here.
Tom
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they all use air in some regard.. theres no other source of energy onboard.Theres no other option
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rkr, does the Steyr auto index the magazine or is it manual? Not any around here.
Tom
Yes, it auto indexes. The system is similar to Steyr LP50 and you can find the exploded diagram for that in here http://www.steyr-sport.com/index.php/en/service-en/download-en/category/22-parts-lists-with-exploded-views (http://www.steyr-sport.com/index.php/en/service-en/download-en/category/22-parts-lists-with-exploded-views)
Unfortunately the magazine is 5 shot only :(
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they all use air in some regard.. theres no other source of energy onboard.Theres no other option
That's right. If the air burst from muzzle is used the losses are miniscule. In blowback mode I'd expect much higher losses, still the caselman manages at least 30 full-auto shots from it's bottle so it's not all that bad. They say air is free ... :P
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a huge factor there is the air supply.. most production pcps have such a small reservoir capacity in the tube compared to the casleman tank.
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Well, I tested the principle with 12 fpe .22 gun using a soft hammer spring and heavy bolt handle - it doesn't cock. I guess it takes a bigbore with heavy hammer and very soft spring to make it work.
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Has anyone (besides me) actually thought of building a Caselman? It is a pretty elegant design, not really challenging for someone with a modest shop and a little experience. With .30 cal pellets and barrels available (no reason not to build any caliber you like), it even simplifies the whole thing a bit.... I have the plans and a pretty thorough build log that clears up some details. I tried posting it, but for some reason, it just won't go. If you're interested, I'll PM it to you. This is a link on the web to the build log I include in my PDF....
http://www.thefirearmblog.com/blog/2014/05/02/32-cal-caselman-air-powered-machine-gun/ (http://www.thefirearmblog.com/blog/2014/05/02/32-cal-caselman-air-powered-machine-gun/)
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Id like to see the actual bluprints/pdf!
Im not sure why almost no one builds them , i always assumed there was vague plans or some inherent design flaw./
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I just mentioned to someone earlier, I must have arthritis of the brain, too. I'm not as quick as I used to be. No way I can post the Caselman file here, cos it's 16.3MB.... Doh! Any if anyone wants to check it out, I posted it to my Google Drive. Here's link to it. Enjoy guys!
https://drive.google.com/open?id=0By9mpxicuctTSUNNVlNTaEN2Ykk
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For my electric repeater XS60C modification, I was originally going to use a motorized "chain gun" system like a lot of electric airsoft guns as a reloading mechanism ("hammer" is an electric solenoid, see http://www.gatewaytoairguns.org/GTA/index.php?topic=103085.0 (http://www.gatewaytoairguns.org/GTA/index.php?topic=103085.0)). Other than using a solenoid as a hammer, using my own bolt, and sawing off the material behind the valve where the hammer and bolt used to be, is an otherwise stock XS60C CO2 version.
I decided to put the new bolt I crudely fabricated alone into the breech (after loading a pellet) and pulled the trigger. The result was both the pellet going down the barrel and the bolt being ejected backwards, clearing the breech. I did the same with the stock XS60C bolt and the same thing happened. This gave me an idea for a pure blowback reload system like you see in "real" pistols and submachine guns.
The first picture is my 3D printed prototype. It's a little finicky due to the geometry of the parts and because I miscalculated the guide rod length and the plastic part of the bolt's geometry.
The second picture is a single screenshot showing the spring loaded bolt clearing the breech area after a single shot was fired in the testing rig. I wish I could export the whole video, but I had to use the SloPro app since my iPhone's default SloMo camera wasn't quick enough to capture the cycle. The bolt does return back to into the breech about 70% of the time, again due to my mistakes in its geometry. Blowback only happens if a pellet is in the chamber which generates enough pressure to cycle the bolt. If nothing is loaded, the bolt will not fly back.
So a blowback system does work for reloading alone. I don't think the air has enough energy to pull back a conventional coil spring loaded hammer like what is on the XS60C.
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awesome , I do think air has enough energy to cock any airgun, granted the return piston would need to be large in some cases. With a 1 inch piston well sealed , and a controlled leak into the cylinder. 1400psi would create up to 1100pounds of rear force.I guess the key would eb finding the ideal balance and not wasting a bunch of air in the processs.
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For my electric repeater XS60C modification, I was originally going to use a motorized "chain gun" system like a lot of electric airsoft guns as a reloading mechanism ("hammer" is an electric solenoid, see http://www.gatewaytoairguns.org/GTA/index.php?topic=103085.0 (http://www.gatewaytoairguns.org/GTA/index.php?topic=103085.0)). Other than using a solenoid as a hammer, using my own bolt, and sawing off the material behind the valve where the hammer and bolt used to be, is an otherwise stock XS60C CO2 version.
I decided to put the new bolt I crudely fabricated alone into the breech (after loading a pellet) and pulled the trigger. The result was both the pellet going down the barrel and the bolt being ejected backwards, clearing the breech. I did the same with the stock XS60C bolt and the same thing happened. This gave me an idea for a pure blowback reload system like you see in "real" pistols and submachine guns.
The first picture is my 3D printed prototype. It's a little finicky due to the geometry of the parts and because I miscalculated the guide rod length and the plastic part of the bolt's geometry.
The second picture is a single screenshot showing the spring loaded bolt clearing the breech area after a single shot was fired in the testing rig. I wish I could export the whole video, but I had to use the SloPro app since my iPhone's default SloMo camera wasn't quick enough to capture the cycle. The bolt does return back to into the breech about 70% of the time, again due to my mistakes in its geometry. Blowback only happens if a pellet is in the chamber which generates enough pressure to cycle the bolt. If nothing is loaded, the bolt will not fly back.
So a blowback system does work for reloading alone. I don't think the air has enough energy to pull back a conventional coil spring loaded hammer like what is on the XS60C.
There's not enough energy to cock a conventional small bore hammer. Caselman uses very heavy hammer and soft spring + .32 caliber probe end to enable the blowback. What many others have used (including FX) is to have a piston inside a barrel shroud that then handles the pullback and cocking of the hammer.
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The SMG .22 from Airordanace maybe what you need to look at.
Hooked to 1250 PSI HPA it will do 800+ FPS.
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The SMG .22 from Airordanace maybe what you need to look at.
Hooked to 1250 PSI HPA it will do 800+ FPS.
If it's Tippmann based it fires from open bolt (not the greatest for accuracy) and is not exactly blowback in similar manner as Caselman. I already have a Drozd Blackbird to play with, otherwise I'd be interested.
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Let's me introduce a home-made pistole, made by my friend from Zaporizzja, Ukraine. His nickname is Zerg007
It's double action - hammer takes air from valve, breech takes a air exhaust from sound moderator. It's double blow-back action :)
(https://img-fotki.yandex.ru/get/6402/221428643.a/0_f281e_3db365ef_L.jpg)
It has 150mm long LW-barrel and regulator. Speed - 200m\s with 0.51g pellet.
There is video in YouTube: - alas, I can't add a full link, so I add only number of video: vY7crMD340Y - You can easy Google the video with help of this number.
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very cool.. seems to work like a paintball marker.