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I've always thought these guns were cool, and always knew getting a real one impossible. Gun building, ho!
My renewed interest in them came when Kel-Tec debuted their RDB carbine last year in 6.5 Grendel. It occurred to me that their little design had the makings of a similar platform to the WA-2000.
-Compact bullpup format intended for position shooting in cramped surroundings
-Accuracy-minded DMR/counter-sniper construction (it's not been optimized by Kel Tec, but the ingredients are there)
-Chambering capable of performing out to fairly long ranges (800-1000+ yards)
I had not been very interested in accuracy-oriented semi-autos because they tend to be on the big side, but the bullpup addresses most of that, and the small but still long-ranged Grendel addresses the remainder. I was once skeptical of bullpups primarily because of design compromises when it comes to ejection, but Kel Tec had addressed that. To be fair, the earlier RFB had these characteristics as well, but I never really warmed up to the forward-ejection system, plus it was somewhat plagued with quality/function issues for a while; they've clearly learned a lot and upped their game where the RDB is concerned, and put out a pretty compelling rifle.
Unfortunately, the Kel Tec RDB in 6.5 Grendel is both unobtainable for the foreseeable future, and kind of ugly imo (I have one in 5.56 that is my favorite rifle, but I won't pretend it isn't a bit goofy looking), which is where this build comes in. Plus, it's an opportunity to combine the best traits of multiple platforms.
Design goals:
-Strut-based tensioned barrel setup in the fashion of the WA-2000. Concentric tube types are easier and work better, but don't look as good. ;D
-Completely ambidextrous design, bottom-ejecting like the Kel Tec. Between the PS90 and the RDB, I've become a huge fan of downward-ejecting systems; truly the best way to facilitate ambidextrous & positional shooting, and by far the best for recovering brass.
-Short-stroke gas piston action, because it is clean (though DI would be less of an issue for the shooter on a well-sealed design like this) and keeps gas away from the shooter
-Bullpup layout, but with a quality trigger. Kel Tec uses a sear local to the trigger to release a linkage that drives the hammer, as opposed to a trigger linkage to release a remote sear as is usually done. Lock time is higher, but the trigger pull approaches that of any other semi-auto design.
-Convenient features like pic-rail optics, adjustable gas settings, adjustable comb & butt.
-Much lighter weight construction than the tank-like WA-2000. My theory is the weaker chambering will impart less force on everything, and allow parts to be lighter & made of aluminum vs. bulky steel while still retaining accuracy.
-Try to improve upon the original as far as how compact the package is; it was rather big for what it was because of the HK-style trigger group below the action, and still muzzle-heavy because of long barrel & heavy steel struts
Concept/Layout;
-20"-22" barrel
-AR18/G36 style gas system; small tappet, a transfer rod, and a short carrier riding on a guide rod/spring assembly and rails
-AR15 bolt head & barrel extension (bolt from the group buy!)
-Two large, round aluminum tubes above & below the barrel to tension it (gas system inside the upper one)
-Beefy aluminum adjustable gas block supports both struts, vents to the front
-Large muzzle compensator is tightened against the gas block to tension the barrel
-Beefy aluminum trunnion supporting the optics, pistol grip attachments, struts, and barrel
-Inverted U-shaped 'bathtub' receiver closed out on the underside by a modular trigger unit & magwell
-Belleville washer tensioning springs at the breech-end between the trunnion & barrel extension
Design Challenges;
-Getting an AR15 bolt to eject straight down when the extractor claw is in line with one of the two lugs needed for feeding
-Getting an AR15 bolt to strip a round using the extractor claw face
-Developing a Grendel short-stroke gas system that taps gas from nearly the muzzle of a long barrel (so very low pressure, high dwell time, but also with a longer than usual bolt travel)
Kind of a large but more detailed depiction of the concept
TCB
My renewed interest in them came when Kel-Tec debuted their RDB carbine last year in 6.5 Grendel. It occurred to me that their little design had the makings of a similar platform to the WA-2000.
-Compact bullpup format intended for position shooting in cramped surroundings
-Accuracy-minded DMR/counter-sniper construction (it's not been optimized by Kel Tec, but the ingredients are there)
-Chambering capable of performing out to fairly long ranges (800-1000+ yards)
I had not been very interested in accuracy-oriented semi-autos because they tend to be on the big side, but the bullpup addresses most of that, and the small but still long-ranged Grendel addresses the remainder. I was once skeptical of bullpups primarily because of design compromises when it comes to ejection, but Kel Tec had addressed that. To be fair, the earlier RFB had these characteristics as well, but I never really warmed up to the forward-ejection system, plus it was somewhat plagued with quality/function issues for a while; they've clearly learned a lot and upped their game where the RDB is concerned, and put out a pretty compelling rifle.
Unfortunately, the Kel Tec RDB in 6.5 Grendel is both unobtainable for the foreseeable future, and kind of ugly imo (I have one in 5.56 that is my favorite rifle, but I won't pretend it isn't a bit goofy looking), which is where this build comes in. Plus, it's an opportunity to combine the best traits of multiple platforms.
Design goals:
-Strut-based tensioned barrel setup in the fashion of the WA-2000. Concentric tube types are easier and work better, but don't look as good. ;D
-Completely ambidextrous design, bottom-ejecting like the Kel Tec. Between the PS90 and the RDB, I've become a huge fan of downward-ejecting systems; truly the best way to facilitate ambidextrous & positional shooting, and by far the best for recovering brass.
-Short-stroke gas piston action, because it is clean (though DI would be less of an issue for the shooter on a well-sealed design like this) and keeps gas away from the shooter
-Bullpup layout, but with a quality trigger. Kel Tec uses a sear local to the trigger to release a linkage that drives the hammer, as opposed to a trigger linkage to release a remote sear as is usually done. Lock time is higher, but the trigger pull approaches that of any other semi-auto design.
-Convenient features like pic-rail optics, adjustable gas settings, adjustable comb & butt.
-Much lighter weight construction than the tank-like WA-2000. My theory is the weaker chambering will impart less force on everything, and allow parts to be lighter & made of aluminum vs. bulky steel while still retaining accuracy.
-Try to improve upon the original as far as how compact the package is; it was rather big for what it was because of the HK-style trigger group below the action, and still muzzle-heavy because of long barrel & heavy steel struts
Concept/Layout;
-20"-22" barrel
-AR18/G36 style gas system; small tappet, a transfer rod, and a short carrier riding on a guide rod/spring assembly and rails
-AR15 bolt head & barrel extension (bolt from the group buy!)
-Two large, round aluminum tubes above & below the barrel to tension it (gas system inside the upper one)
-Beefy aluminum adjustable gas block supports both struts, vents to the front
-Large muzzle compensator is tightened against the gas block to tension the barrel
-Beefy aluminum trunnion supporting the optics, pistol grip attachments, struts, and barrel
-Inverted U-shaped 'bathtub' receiver closed out on the underside by a modular trigger unit & magwell
-Belleville washer tensioning springs at the breech-end between the trunnion & barrel extension
Design Challenges;
-Getting an AR15 bolt to eject straight down when the extractor claw is in line with one of the two lugs needed for feeding
-Getting an AR15 bolt to strip a round using the extractor claw face
-Developing a Grendel short-stroke gas system that taps gas from nearly the muzzle of a long barrel (so very low pressure, high dwell time, but also with a longer than usual bolt travel)
Kind of a large but more detailed depiction of the concept
TCB
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