RIS play
 

Have a g&p mk18 mod0 and I noticed that the RIS with the tactical foregrip installed has a bit of a rotary play. It's not rock-solid as my other m4 with a RAS.

Here is what I found...

RIS is secured by a tab of the upper handguard against the front handguard cap. In my case I don't see one. There is just a flat head screw that after tightening, it has no effect.
http://i6.photobucket.com/albums/y21.../DSC_6768_.jpg

After some online research I got to remove the upper hand guard and there's the tab...
http://i6.photobucket.com/albums/y21.../DSC_6792_.jpg

The cross-section of the tab itself, it's concave and same shape of the the front handguard cap as it would be resting on it.
http://i6.photobucket.com/albums/y21.../DSC_6790_.jpg

After re-installing correctly:
http://i6.photobucket.com/albums/y21.../DSC_6795_.jpg
The little rotary play is still there. That play comes from the handguard cap which is secured by the outer barrel and the gas tube.

Is this normal?

The difference with the RAS, it has a tab on the other end (upper receiver), that when you tighten the screw (usually allen), it grabs/clings with barrel nut; and that tab has a cut-out which passes the gas tube, thus preventing it from rotary play once tightened.

in your last picture, that tab still has to go in the front cap. I think the reason why it still has play is because of the last sentence you wrote. I dont think they replicated the RAS properly like the real one from KAC. I think your other M4 is stable because of the prong like nature of that bar which clings to the barrel nut once you tighten the screw. without that, the bar is pretty much useless.

I can confirm that this gun's RIS is not correctly modeled after the real KAC RIS. I own both, and the G&P RIS is "backwards" for lack of a better term... but really it's just wrong. The screw on the KAC RIS is at the Delta ring, and has a latch that goes around the gas tube, and under the delta ring, when secured bolts the whole upper assembly down securely.

The G&P RIS has a screw at the front, which holds a spring latch against... itself, and doesn't hold anything in place. The whole assembly is held together in the exact fashion as the stock polymer hand guards, with tension from the delta ring.

I had to shim the interface between the barrel nut and the G&P RIS to fully get rid of the wobble.

I think they manufactured it like the KAC RIS. On the lower half of this thread:
http://jobrelatedstuff.com/mobile/to...08319&page=123

I think RIS would be really wobble-prone as it is secured on the hadguard cap; plus of course on the delta-ring tension.

While here's how the "RAS" is installed:
http://www.quarterbore.com/library/p...c_ras_inst.pdf

That's weird... I had a G&P mk18 mod 0 front set on a gun of mine last year and when I had the gas tube in it didn't wobble at all.

Have to agree just from looking at the pics, this RIS looks entirely wrong (even the markings). The WE RIS is modeled after the real one and it's not going anywhere; this one just seems poorly designed.

a really quick and easy solution is one of these
http://madbull.com/catalog/index.php...products_id=50
I'm not sure if anyone in Canada sells them but I have seen them occassionally on a few retailer's websites.