I just stumbled upon the RRA "R-4" barrel profile.  JT Distributing also has one that looks to be the same and is called the "EM-4"  It looks to be an Hbar with the M203 notch in the barrel.  Does anyone konw if this is the case?  Or is it more like an M4 profile that is extra thick under the handguards? (pardon me, maybe the Hbar and M4 are the same diameter in front of the handguards, I am not too familiar with them)

If anyone has some specs (barrel weight, dia in front and behind HG, etc.) Also, if anyone knows if you can mount a 37mm M203 clone on one of these (more just curious) or if the extra thickness makes it impossible, I would like to know!


My M4 barrel heats up a lot faster than I like, and I think a chrome lined R4 is exactly what I am looking for.

An M4 barrel is the same as an HBAR from the front sight forward, except for the notch.

The R-4 barrel:
[img]http://www.rockriverarms.com/images/bblr4.gif[/img]
Seems to be an HBAR with the notch for looks.  It would heat up (and cool down) slower than a real M4 barrel that's thin under the HGs.  An M203 would not fit because it needs a thin area under the HGs as well as in front.  (The "heavy M4" has a second notch, but it's still thinner than an HBAR under the HGs.)

The EM-4 barrel:
[img]http://webcats.net/store/graphics/00000001/20_mck_m4.jpg[/img]
Looks to me like it's a little thinner than the RRA one, but it's hard to tell from the picture.  It's definitely thicker than a regular M4 and wouldn't mount an M203 either.

If RRA and J&T no longer make a "real" M4 profile (thin under the HGs) then they've taken a giant step backwards IMHO...

RRA still has light under the HG R4 bbls as an option...generally on the post-bans with the pressed-on mock suppressor.  For whatever reason it doesn't appear in the catalog or on their site.
Sluggo