King Arms vs. Boyi C.A.S.V. Comparison / Review

Late last year, a certain rail system caught my eye. Looked like it came out of a low grade SciFi movie where they have to kind of make do with what they have.

King Arms released a C.A.S.V. Rail Integration System.
Within a year, the Chinese had the prints and had a "clone" C.A.S.V. on the markets.

A small background of the VLTOR CASV-EL rail system can be found here.

What is the CASV for airsoft?
The CASV is a free floating hand guard, that allows the user to mount 1, 2, or 3 inch rails at various mounting points on the hand guard. Mounting points include the top spine rail, each of the sides of the hand guard, the bottom of the hand guard, and the ability to mount rails at a 45 degree angle on the bottom side of the rail system.
In my personal experience and usage of this rail system, the ability to mount a rail at virtually any spot / angle that I could utilize has come in handy more times than you can think.
For one skirmish I could install every rail that the kit came with, loading various accessories onto the rifle. The next day I could take off all of the rails and accessories and use the rifle for just the hand guard.
As stated, this rail system has proved itself very useful, practical, and taticool!!!!

Review and comparison of the two rails...
Thanks to Armsdealer for providing a sample Boyi rail to compare to a King Arms rail purchased from UNCompany.

King Arms
Weight: Approximately 1lb 2.3oz with rails, 14oz without rails
Length: 352mm (Approx. 13.86 inches)
Width: 72mm with rails attached / 53mm without rails attached
(Approx 2.83 inches with rails / Approx 2.09 inches without rails)
Price: $169.99 + shipping (Price taken from Evike.com)

Boyi
Weight: Approximately 2lbs 4oz with rails, 1lb 5oz without rails
Length: 352mm (Approx. 13.86)
Width: 74mm with rails attached / 54mm without rails attached
(Approx. 2.91 inches with rails / Approx. 2.13 inches without rails)
Price: $65 from AirsoftBattleZone

All pictures will be posted at the end of the review in link forms to make this review friendly for all internet users.

There are several obvious differences in the two rail sets. One of the biggest differences being the weight of the rail. Pickup the King Arms version and then pickup the Boyi version, and you'll see the differences. The Boyi version might make your gun a bit more front heavy, but if you balance it out with a full or crane stock, it'll work out just nicely.
As you can see from the weights above, the King Arms rail weighs a bit less than the Boyi rail, but is still just as strong and sturdy when holding onto it.

The Lower portions of the C.A.S.V. rails are similar looking, but constructed just a hair different. With modifications the rails could be interchangeable.

Another one of the differences with the rails that you'll see right away is the inside of the rail itself.
While the King Arms is very spacious inside, the Boyi rail has dividers on the inside a little behind the front sight. What these dividers are for, I am not entirely certain. They look to small to be dividers for a battery, or to serve any real purpose to enhance the rail system, other than reinforce the shell of the hand guard.
Where the King Arms version has supports in the same locations, they do not protrude into the rail nearly as much.

Another part of the interior of the C.A.S.V. that you will see protruding is the screw holes to mount the rails.
Where the King Arms version screw holes stick out just a small amount, still allowing ample room for a battery if desired, the Boyi's screw holes stick out quite a bit. This could make any kind of internally held battery somewhat tricky, if at all.

In the Boyi version, the support / dividers and the screw holes, will most likely prevent any "normal" battery being used inside of the grip itself without modification.
The King Arms version, you will easily be able to fit 8.4v and 9.6v mini size batteries with no modifications.

The last part on the inside of the hand guard you'll notice is a little different between the two versions, is the delta ring "lock."
The King Arms version closely replicates the actual VLTOR C.A.S.V. by using a small rail allows the delta ring to sit inside of it, and help lock in and solidify the upper hand guard. This requires a "new type" delta ring, the stock Marui delta rings will not work all to easily, and will require modification.
The Boyi version seems to have eliminated this "lock," making it probably universal on any flat top receiver. Big bonus for the Boyi user!

Onto the externals and functionality of the two...

With there being little to say really, as the rails are ALMOST and exact copy of each other, there are a couple nit picky differences between the two.
First of which being the screws... I know you might be sitting there saying, "So what, I put it on once and then just leave it be, what do I care?"
Heres the kicker though....
I went through SEVERAL different variants of my M4 with C.A.S.V. installed, and the biggest bonus of having the King Arms version was how they used one screw head size for the entire rail. I didn't have two swap tools or bit heads half as much, meaning less time tinkering with the gun, more time playing.
All of the screws took the same 3.0 hex, which made it very easy to take off, and put on the hand guard and accessory rails.
The Boyi version uses two different screw heads. A 3.0 to mount on the hand guard to the flat top receiver, and 4.0 hex to mount on each of the accessory rails.

Once again, not a big deal unless your going to be taking it down for every game and customizing it "special" for each game.

One thing that could possibly lead to problems is how the hand guard closes on the Boyi version.
The King Arms version itself has tabs that stick out, and are very stiff, so they lock in place very easily. I've wrenched on it numerous times, only to have the hand guard stay put, and not even wobble.
The Boyi version, I've pulled it apart with little force when the tabs are looking as if they are locked in place.
This could be due to wear on the tabs, as they seem to be thinner / weaker metal than the King Arms version. But I myself have put the King Arms tabs to the test, taking them off 3+ times a week for almost 6 months, and they still lock into place securely, and are still very stiff when trying to take the lower hand guard off.

Last thing you'll notice externally, as there are not too many differentiating feature between the two, is how the hand guard is attached to the "spine rail."
On the King Arms version, the hand guard appears to be pop riveted onto the rail. You cannot separate the two, making it a solid unit.
The Boyi version, the hand guard is attached to the rail with three 4.0 hex screws. This might be a "cool feature" with the rail, but in the end it could also be another worry spot if you do not apply a little bit of Loctite onto the screws. Vibrations from the gun could lead to the screws loosening and possibly falling out of any spot on the gun if they are not watched and properly installed.

Simply put... If you want that VLTOR look for a cheaper cost... Boyi is the way to go. The rail is well worth the $65 price tag, and is a very close "clone" of the actual rail. With a couple tweaks here and there, any of the possible "worry / problem spots" that I've mentioned could be fixed and possibly improved upon.

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Top painted CASV is the King Arms version
Lower black CASV is the Boyi Version

Inside view through the King Arms version
Inside view through the Boyi version
You can definitely see the difference in the interiors of the rails. The Boyi version having much more protruding into the hand guard than the King Arms version.

Quick view at the insides of the two rails when opened up

Closeup of the insides of the King Arms version
Closeup of the top portion of the King Arms version
Closeup of the lower portion of the King Arms version


Closeup of th einsides of the Boyi version
Closeup of the top portion of the Boyi version
Closeup of hte lower potrion of the Boyi version


The CASV

Reviewer : A-Ron
Reviewed : 10 Sep 2007