I have a rail mounted 9" M203 that I planned to mount onto a MR556.  However, I'm thinking to build a rifle dedicated for the M203, particularly a clone of some sort in use by the military and I'm a bit ignorant on the subject.  Most of the mounted M203s I've seen are barrel mounted.  Are there any examples of rail mounted versions in current use?

Would a rail mounted M203 on a 10.5" DD MK18 upper be "correct"?  If there's no examples out there to clone, then the other option I was considering was an LMT MRP upper simply for the added strength of the monolithic design.  Thanks for any advice.

The Mk18 RIS II does not accept a 203. The full length RIS II, does however.

I've seen 1 203 okie rigged to an actual Mk18 (KAC M4 RIS, not DD RIS II) and it looked pretty sketchy.

So the answer is no, you cannot mount a 203 to a DD "mk18" upper.

Wouldn't an LMT M203-R with a 9" barrel fit?



Yeah, I can see it might be a stretch...

Even ignoring the length issue, the Mk18 RIS II doesn't have M203 hangers/tabs. The full length M4A1 RIS II does, however. (I have them installed on mine)

I think that one just mounts directly to a picatinny rail.

are we talking 40mm or 37mm in this thread

if 37mm I think you may want to look into the  havoc much closer to the fnh launcher it may be in very limited iussue but I think you're gonna need a step down m-4 barrel or a rail mount

gnh gl1

spikes 37mm side loader
in 03 i was issued a colt m4 with a 203  the ris  it HAD NO 6:00 RAIL IT HAD THE LEAF SIGHT AND A PAQ4 it was barrel mounted with the knights qd mount.   it was kinda useless the m68 cco blocked the view of the leaf sight & it weighed about 14 lbs with grenade & mag loaded,

In that case it could work..I assumed we were talking about a traditional M203 here. I'm not familiar with that one.

Needs more KAC URXII....

I'm referring to the 40mm version that mounts to a picatinny rail.

I found this picture, so it looks like it will mount up with no issues?  But I'm guessing from the replies, this isn't a standard issued setup used by our military?  Might be my only option though for a clone like MK18 M203 using the picatinny railed version?  Thanks again!

That's definitely a civilian rifle. But as far as the M203's I've seen in use (standard, not picattiny mounted) they won't mount to the block 2 CQBR.

I'm not sure if the military has any of these LMT picattiny 203's, but I've never seen em'

So no, this wouldn't be standard issue. All the 203's I've seen pics of on mil RIS II's was on the 14.5

I'd feel much more comfortable with the standard 203 and M4A1 RIS II hangar tabs personally. As you said, the thought of pic mounting a 203 on a RIS II bottom rail seems kinda sketchy. Although it would prob work if it fits ok on the short RIS II

easiest solution: build a GL/SSC.

More like the hardest solution.

I only know of 1 GL/SSC rail in existance! And he hasn't posted it in a while, wonder if it went bye bye.

While it could be argued that the average civilian is not going to shoot enough 40MM for it to really make a difference, IIRC, the LMT rail-mounted M203 was more or less designed as an MRP accessory since the LMT MRP does not have a removable bottom rail to barrel mount the M203 - however, since it's a "true" monolithic, it has the strength and rigidity to support the M203.  

I would think it would more or less fairly well on a one-piece quad rail, but I don't think I'd be comfortable putting it on a removable bottom rail design and/or "modular" handguard where only a couple of bolts are supporting the launcher and attaching it to the rifle.  

Not the the M203 is a super-heavily or intensely recoiling device... but I'm pretty sure I've seen some bent rails from using them with the rail-mounted '203.  

If/when I get a '203, it will be the barrel mount version.  

The ironic thing, however, is that the M4A1 RIS II was designed with a specific requirement to free-float an M203... but many of the units using the RIS II are now using the M320A1, and thus having to go back to using it with the KAC M4 RAS.  





~Augee

Both the M203 and 320 a was issued were on M4s.

Then again I was not a high speed operator that had a MK18, so I am not sure if it would work.