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Posted: 1/29/2015 2:15:44 PM EDT
[#1]
I'm sure a blowback .223 rifle could be made. Not in the AR platform though.
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Posted: 1/29/2015 2:44:36 PM EDT
[#2]
Quote HistoryQuoted: I'm sure a blowback .223 rifle could be made. Not in the AR platform though. It's been made. Saw a pic of an AR magazine fed rifle in one of the Hispanic drug war seizure pics. In Mexico or Brazil, maybe. Looked like a STEN married a HiPoint. What would a rifle buffer full w/ tungsten weights & a 9x19mm blowback bolt weigh? |
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Posted: 1/29/2015 2:53:03 PM EDT
[#3]
You could try a heavy buffers 11oz rifle buffer.
http://www.heavybuffers.com/ar15rifle.html I'm pretty sure your still going to need more weight. |
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Posted: 1/29/2015 3:17:29 PM EDT
[#4]
That'd be scary us. Really scary us for lefties.
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Posted: 1/29/2015 4:14:45 PM EDT
[#5]
Blow back designs are OK for pistol cartridges but the camber pressures of rifle cartridges you need a locking system.
Just look at the pistol designs like the High Point 45. Giant slide to hold the slide closed (by mass) for the few micro-seconds it need to get the projectile out of the barrel. That chamber pressure is less than 28,000 psi (that's 45 super). Trying to hold the bolt closed with bolt mass for a cartridge that has a chamber pressure of over 62,000 psi would have to be massive. |
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Posted: 1/29/2015 4:49:32 PM EDT
[#6]
MG42/34 worked on a combination of recoil/ blowback, 7.92mm, bolt was locked with spring loaded ball bearings, I may be wrong though
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Posted: 1/29/2015 4:52:33 PM EDT
[#7]
Quote HistoryQuoted:
MG42/34 worked on a combination of recoil/ blowback, 7.92mm, bolt was locked with spring loaded ball bearings, I may be wrong though "Roller-delayed" is the important part. That is a locked breech. |
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Posted: 1/29/2015 5:57:18 PM EDT
[#8]
Quote HistoryQuoted:
MG42/34 worked on a combination of recoil/ blowback, 7.92mm, bolt was locked with spring loaded ball bearings, I may be wrong though What? Ah....................................No |
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Posted: 1/29/2015 7:26:49 PM EDT
[#9]
Quote HistoryQuoted:
"Roller-delayed" is the important part. That is a locked breech. Quote HistoryQuoted:
Quoted:
MG42/34 worked on a combination of recoil/ blowback, 7.92mm, bolt was locked with spring loaded ball bearings, I may be wrong though "Roller-delayed" is the important part. That is a locked breech. If I'm not mistaken, wasn't that the predecessor to the modern day H&K roller locker system? |
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Posted: 1/29/2015 7:35:41 PM EDT
[#10]
Quote HistoryQuoted:
If I'm not mistaken, wasn't that the predecessor to the modern day H&K roller locker system? Quote HistoryQuoted:
Quoted:
Quoted:
MG42/34 worked on a combination of recoil/ blowback, 7.92mm, bolt was locked with spring loaded ball bearings, I may be wrong though "Roller-delayed" is the important part. That is a locked breech. If I'm not mistaken, wasn't that the predecessor to the modern day H&K roller locker system? The HK is a modified version. |
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Posted: 1/29/2015 8:55:09 PM EDT
[#11]
MG38 and MG42 were RECOIL operation systems that used a "roller" locking system. the were a wee-bit more than spring loaded ball bearings. OK... they were roller bearings, but they were held in place with a hellva wedge.
That locking system went into the Stg 45 (that was the Granddaddy to the H&K G-3). HK G-3 has a solid barrel with "flutes" in chamber to drive gas energy into bolt face to the gas operated roller delayed operating system. |
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Posted: 1/29/2015 8:59:15 PM EDT
[#12]
Quote HistoryQuoted: You could try a heavy buffers 11oz rifle buffer.
http://www.heavybuffers.com/ar15rifle.html I'm pretty sure your still going to need more weight. Yeah, like 5 lbs more.
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Posted: 1/29/2015 9:30:02 PM EDT
[#13]
Some one on here had a link to a blowback gun calculator A 223 would need a breechblock that looked like it came from a ww2 anti tank cannon.
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Posted: 1/30/2015 9:18:47 AM EDT
[#14]
I would not say it can’t be done, but given how heavy the bolts in MAC’s and grease guns are I would imagine it would be a sight to see.
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Posted: 1/30/2015 11:05:31 AM EDT
[#15]
My Class III dealer/manufacturer made a blowback AR .223/5.56 2" barrel   |
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Posted: 1/30/2015 11:22:15 AM EDT
[#16]
Quote HistoryQuoted:
Blow back designs are OK for pistol cartridges but the camber pressures of rifle cartridges you need a locking system. Not really. With enough mass behind, you can build anything blowback. Is it practical? No. It would be too heavy. |
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Posted: 1/30/2015 11:39:14 AM EDT
[#17]
Quote HistoryQuoted: Not really. With enough mass behind, you can build anything blowback. Is it practical? No. It would be too heavy. Quote HistoryQuoted: Quoted: Blow back designs are OK for pistol cartridges but the camber pressures of rifle cartridges you need a locking system. Not really. With enough mass behind, you can build anything blowback. Is it practical? No. It would be too heavy. See my post above |
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Posted: 1/30/2015 12:59:34 PM EDT
[#18]
Quote HistoryQuoted:
Not really. With enough mass behind, you can build anything blowback. Is it practical? No. It would be too heavy. Quote HistoryQuoted:
Quoted:
Blow back designs are OK for pistol cartridges but the camber pressures of rifle cartridges you need a locking system. Not really. With enough mass behind, you can build anything blowback. Is it practical? No. It would be too heavy. Didn't ask about practicality. I asked if it could be done. 
I don't think you can stuff enough tungsten in a rifle length buffer and the open end of a 9x19mm blowback bolt to make it work. You'd need a custom receiver extension w/ a much larger buffer. |
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Posted: 1/30/2015 6:13:50 PM EDT
[#19]
'Blow-back' 5.56 = 'Blow-Up'!
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Posted: 2/2/2015 2:22:38 AM EDT
[#20]
Quote HistoryQuoted: 'Blow-back' 5.56 = 'Blow-Up'! It would seem that someone has tried the idea before: 
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Posted: 2/2/2015 12:54:51 PM EDT
[#21]
How does the Keltec PLR series fit into this discussion? I know it's a 5.56 piston system without a buffer system, and maybe that's the only unique aspect compared to a pure AR design. The term "blowback" actually seems to cover a really large category of firearms. Is this more of a "locked breech" vs "unlocked breech" discussion?
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Posted: 2/2/2015 1:41:34 PM EDT
[#22]
Quote HistoryQuoted:
How does the Keltec PLR series fit into this discussion? I know it's a 5.56 piston system without a buffer system, and maybe that's the only unique aspect compared to a pure AR design. The term "blowback" actually seems to cover a really large category of firearms. Is this more of a "locked breech" vs "unlocked breech" discussion? The Keltec PLR, as far as I know, unless I'm thinking of something different is a fairly conventional gas operated piston design, the fact that it does not have an in-line buffer extending from the receiver is simply a design decision, and no different than e.g. the FNH SCAR/CAR-family, or AR180/18 inspired designs. http://en.wikipedia.org/wiki/Blowback_%28firearms%29 ~Augee |
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Posted: 2/2/2015 1:43:32 PM EDT
[#23]
Quote HistoryQuoted: How does the Keltec PLR series fit into this discussion? I know it's a 5.56 piston system without a buffer system, and maybe that's the only unique aspect compared to a pure AR design. The term "blowback" actually seems to cover a really large category of firearms. Is this more of a "locked breech" vs "unlocked breech" discussion? Blowback, not delayed blowback, or retarded blowback, is an unlocked breech that delays opening by the sheer mass of the bolt. In a 5.56x45mm firearm, it's gonna require somewhere in the neighborhood of a 5 lb bolt for a semi-auto. Open bolt full-auto about halves that. |
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