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Project Valerio: 3C 1B by Hoborginc Project Valerio: 3C 1B by Hoborginc
This is a select-fire platform chambered in 6.5 Grendel, a round selected for its relatively compact size and velocity retention at long distances.

The weapon consists of an aluminum upper receiver containing a steel bolt carrier group with an extended gas key, which envelops the gas tube and is in turn enveloped by the return spring. The barrel has a set of locking lugs, which rest inside a steel chamber component. The lower receiver is polymer, as is the handguard and buttplate. The top rail is part of the upper receiver, but additional rails can be attached to the handguard in the 9, 10, 2, 3, and 6 o'clock positions, at the armorer's discretion. The weapon uses proprietary magazines.
There is a sling attachment loop under the buttplate, and multiple points on the handguard where additional sling loops can be inserted. These points can also be used to attach rails.

Pull back the charging handle and push it down to lock the bolt carrier to the rear.
Insert a magazine.
Push one of the Bolt Release buttons OR push the charging handle up, to chamber a round.

Push the Selector down 90 degrees for fully automatic fire.
Pull the trigger. This pulls the connector forward, releasing the hammer. The trigger keeps the connector's sear from re-engaging, so the hammer will continue operating until the trigger is released.

Move the selector to the 45 degree position for semi automatic fire.
Pull the trigger. There are a set of protrusions on the selector which, on the semi-auto position, disengage the connector from the trigger when the weapon is fired. The connector's sear immediately locks the hammer. Releasing the trigger will re-engage it with the connector.

When the last round is fired, the bolt carrier locks to the rear (the charging handle does not, as it is non-reciprocating).
Acquire a new magazine, push the Mag Release up, and secure the empty magazine.
Insert the new magazine.
Push one of the Bolt Release buttons to chamber a round.

Twist the front of the gas block clockwise and pull the gas valve forward, disengaging it from the gas tube.
Push the Handle Release Button to open up the Barrel Handle, which naturally rests in a hollow in the 8 o'clock position.
Opening the handle reveals the Barrel Unlock Button, on the inner part of the mechanism between the handle and barrel.
Push this button, enabling the barrel to rotate. Rotate it clockwise, until the handle is in the 9 o'clock position.
Pull the barrel out of the receiver, holding it by the handle.

Insert the new barrel into the receiver, with the handle horizontal at the 9 o'clock position.
Turn the handle down, to the 8 o'clock position, and fold it into its niche by pushing the Handle Release Button.
Twist the front of the gas block counterclockwise and re-engage the valve to the gas tube.

Push the Buttplate Release buttons on both sides, unlocking the buttplate.
Swivel the buttplate downward.
Push the Takedown Buttons on both sides, freeing the upper and lower receiver.
Swivel the lower receiver down. At this point it remains connected only via the Pivot Pin, and all internals are accessible.

The Selector, Bolt Release, and Mag Release are identical on both sides.
The ejection port and charging handle window are likewise mirrored.
To reverse the Charging Handle, unscrew it from its position in the Charging Handle Sleeve and attach it on the opposite side.
To reverse ejection, replace the bolt with a mirrored bolt. Remove the ejection port cover and attach it on the opposite side.

The Cavalier Compatible Carbine is a compact weapon useable from horseback, while retaining admirable ballistics at range. The short top rail significantly limits sight radius, so the use of optics is highly recommended.
The weapon is capable of being used in a designated marksman role, and, although it is possible to replace the barrel in the field based on the engagement envelope, it is recommended for an armorer to specifically outfit dedicated DMR-configured weapons beforehand, in order to attach components such as the marksman's buttplate and cheekplate, long range optics, bipod, etc. The rails on the weapon are compatible with aftermarket attachments, and limited only by available rail space. For a marksman's rifle, the use of an offset reflex sight (as pictured) is recommended.

Previous prototype is viewable here.
The barrel handle was originally meant to serve as a vertical foregrip, similar to the Steyr AUG. It was moved to the side to accommodate a bottom rail.

In order to overcome the 6.5mm cartridge's unsuitability for belt-fed use and to take advantage of the Cavalier Convertible Carbine's quick barrel-change capability, the next step in the design will be the development of a Light Support Weapon variant. The primary component in this configuration will be a top-feeding upper receiver with an offset gas system, to allow the use of high-capacity magazines without affecting weapon handling while prone.
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Top-Agent-PGG-jr Featured By Owner Aug 3, 2014
Good. I have found a competitor for my IBR-24 assault rifle which is chambered for the same type of round. Playlist:…
gougougougou Featured By Owner Oct 2, 2012
is there a 3D paper model of it?
Hoborginc Featured By Owner Oct 2, 2012
Swordsdragon Featured By Owner Apr 13, 2012
Great! ^^
Skidracer21 Featured By Owner Mar 26, 2012
I see a strong resemblance to the Kel-Tec RFB.
Forgottev-Vestige Featured By Owner Feb 7, 2012
Man, this thing looks like the bastard child of an L22 Carbine and an H&K. And it sounds wonderful. There is one problem I see with it, however - the mag release. It looks like it would be awkward to use. Maybe I've got the general measurements off in my head, but it seems like it would be a pain in the ass. It seems like it could be in a better position - maybe move it forward a bit.

I may also be biased about this part, but I'd also think a 6.5x25 CBJ conversion kit with a 13" barrel wouldn't be amiss. It would provide shooters with better ballistics in the shorter barrel.

Sorry if any of that sounded rude, this is just coming from a hopeful arms designer. You really did do a great job.
Hoborginc Featured By Owner Feb 7, 2012
I'm not very familiar with 6.5x25, but it certainly sounds interesting. In a CQB role where the Grendel can't be used to its full potential, I'll certainly believe that a PDW-type cartridge would be better suited for the job.

The mag release was meant to be pushed with the index finger of the free hand that's changing the mag, or just pushed with the new mag for speed reload, a la AK except in a different direction. However, I can see how that limit's the user's options. Perhaps an optional extended mag release would solve the problem.
ScrewfaceRomeo Featured By Owner Feb 7, 2012  Hobbyist General Artist
I think that actually the Grendel would be better than the 6.5 x 25, 6.5 x 25 is a pistol caliber round if I'm correct, on the whole point of the Grendel was it good for CQB, I mean, LAPD SWAT and the SEALs use it for that purpose so you know it's got Something in that area
SpillnerLoL Featured By Owner Feb 5, 2012
Looks great!
ScrewfaceRomeo Featured By Owner Feb 4, 2012  Hobbyist General Artist
I must say, although I applaud the use of 6.5 Grendel, the Direct Impingement system is dogshit on a stick. When it doesn't melt away all your oil, it fills the chamber with carbon fouling and jams the gun. And I'm always very suspicious of tube-based gas systems, too easy to break. Slap a nice short stroke piston on there, and you'd have an excellent weapon!
Dystatic-Studio Featured By Owner Feb 5, 2012  Professional Digital Artist
The alternative solution is using even larger caliber ammunition, the famous example is the Stoner's first ever assault rifle, AR-10. Reported an extremely well-functioning and highly-durable no matter how strained it is. Thanks by the least 3KG gas compression it can even unjam the gas tube by its own firing.
ScrewfaceRomeo Featured By Owner Feb 5, 2012  Hobbyist General Artist
But that doesnt stop the carbon build up in the chamber, or the bolt from overheating and cooking off the lubricant, which are the biggest reliability issues
Hoborginc Featured By Owner Feb 5, 2012
The LR-300-style system bleeds off some gas from the gas tube, so the amount actually going through the bolt carrier is minimal. The extended gas key's function is somewhat reminiscent of an inside-out long-stroke piston. Furthermore, jamming issues can be alleviated with a more powerful return spring..
ScrewfaceRomeo Featured By Owner Feb 5, 2012  Hobbyist General Artist
A more powerful spring costs more money, as does a complicated inside out piston, when a short stroke would do the same or better for much less. Logistics wins wars, and when you can field the same results for less money, you can put more guys with better gear and food out there. No military is gonna take complicated over simple, or expensive over cheap, provided the performance is the same. (unless it's the U.S. military, or as I like to call them: Colt Defense's bribe bucket). Also, this guy is writing on a biased pro-AR website, with no videos to prove him right, I wouldn't trust that kind of source.
cityofthesouth Featured By Owner Feb 4, 2012
Nice, a great example of what the contest is trying to achieve. Very well done.
Super6-4 Featured By Owner Feb 4, 2012  Hobbyist General Artist
So much detail! Nice!
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