Hi all,

I'm putting together two rifles. Both are RRA flattops, one a carbine 16" M4 profile, the other a standard 20" barrel.

I'd like to get LaRue rails for both rifles. My questions are:

1. For the M4 barrel with carbine gas system, am I restricted to the LaRue 7.0 or can I use a low profile gas block and go for a longer version? I've seen some neat RECCE type builds, but most people seem to be using a mid-length gas system for those.  Will my carbine length work with a LaRue 12 or 13.2? Any disadvantages using a carbine gas system for a RECCE build?

2. For the 20" upper, I'd like to use a rail-mounted front sight on a LaRue rail. If I use the 13.2 rail, will this cover up the low profile gas block and leave a neat front end?

Stupid questions probably, but want to be sure before I order anything. Thanks for your help!

Quoted: 1. For the M4 barrel with carbine gas system, am I restricted to the LaRue 7.0 or can I use a low profile gas block and go for a longer version? I've seen some neat RECCE type builds, but most people seem to be using a mid-length gas system for those.  Will my carbine length work with a LaRue 12 or 13.2? Any disadvantages using a carbine gas system for a RECCE build?

Yes, with a low profile block you can use as long a rail as you wish. I recomend getting a different barrel for two reasons. Firstly, an M4 barrel is not going to be the most accurate of barrels, and I dislike the profile (YMMV). Secondly, a midlength has some advantages (reliability, softer operation) over the shorter gas system, and if you're getting a 16" barrel anyway, the short gas system is a step backwards.

2. For the 20" upper, I'd like to use a rail-mounted front sight on a LaRue rail. If I use the 13.2 rail, will this cover up the low profile gas block and leave a neat front end?

Yes. PRI and Troy make good flip front sights.

Quoted: Hi all, I'm putting together two rifles. Both are RRA flattops, one a carbine 16" M4 profile, the other a standard 20" barrel. I'd like to get LaRue rails for both rifles. My questions are: 1. For the M4 barrel with carbine gas system, am I restricted to the LaRue 7.0 or can I use a low profile gas block and go for a longer version? I've seen some neat RECCE type builds, but most people seem to be using a mid-length gas system for those.  Will my carbine length work with a LaRue 12 or 13.2? Any disadvantages using a carbine gas system for a RECCE build? 2. For the 20" upper, I'd like to use a rail-mounted front sight on a LaRue rail. If I use the 13.2 rail, will this cover up the low profile gas block and leave a neat front end? Stupid questions probably, but want to be sure before I order anything. Thanks for your help!

a RECCE is built with a carbine length gas system for the Mil. midlengths have some advantages. less recoil impulse for one. if your looking to build "Recce" looking build for cheap couldn't you just shave down the FSB? it will be covered. will the rail fit over it?
here's a good read on Recce
http://www.ar15.com/forums/topic.html?b=2&f=134&t=147029

yes and yes
longer rails will give you more options with mounting gear but at the same time might throw off your balance and add wieght .



what are your plans for these rifles?