I can get free-float forearms in a variety of lengths.  The decision seems to be, do I get a short one that allows me to use a gas-block mounted front sight post, or a longer one that covers the gas block, then mount my front sight on a rail?

My goal for this rifle is light and quick.  My lower receiver is a magnesium alloy, and weighs about as much as a paper clip, so I want to let that choice define the build philosophy.  Thus the lightweight profile barrel. 

At the same time, I do want the gun to be as accurate as it can.  Which, for iron sights, means maximizing the sight radius.  So is it worth the added weight of a longer forearm to gain a few inches of sight radius?

Furthermore, I think that I do NOT want a forearm with a continuous rail.  Rails add weight, but how often will I need to mount an accessory over the barrel?  Not often, I think.  I'd rather have a forearm that allows me to attach sections of rail as needed.  Those of you who know me know that I am not into accessories.  The only things I'm even considering at a sling and a light.

So, short forearm and sight post, or long forearm and rail-mounted front sight?

Here is a helpful chart:   https://spreadsheets.google.com/pub?key=pwswheghNQsFnUZMkZNF2DQ&output=html

http://www.midwestindustriesinc.com/index.cfm?fuseaction=category.display&category_ID=450

You could always go with a modular hand-guard and place small rail sections if needed (like for a light).  There are rail sections that have a QD sling hole in the rail piece too so you could use just one rail piece for your sling and light.  The link above is just an example as there are a ton of options out there and they are all pretty light.  IMO you get the benefits of a longer sight radius and a more comfortable hold.  I'm tall so I like the 12-15" rails personally.  There are also a ton of options for BIUS, and if you want to save a little weight (very little) you could go with polymer sights.  Magpul makes MBUS and now the MBUS Pro.  Good luck 

it really depends on the look, the weight, and function you like...and also your budget.....AR15 is big boys' equivalent of legos.

It might be easier to consolidate all your questions in one thread.  Easier to follow.   

Again, the fixed front sight base is the most rugged set up and what I prefer on a defensive rifle.  I will say that modern rails and gas block set ups with rail mounted sights do well for back up sights.  But be aware that a shift in the forend can throw off you zero for rail mounted irons, much easier than a fixed front sight base.  Again modern FF rails and quality irons are pretty darn solid.  Not overly exited about the magnesium receivers, but a light rifle is a plus.  If accuracy is a big deal then perhaps a stainless barrel is a good choice but the trade off can be a bit more ounces.  While weight is important, rifle balance can offset how the weapon performs transitionally.  In reality a good defensive rifle should include irons, a quality optic, sling and a light, so rail choice is wide open.  The minimalist type tube rails are probably your best bet in keeping the rifle lightweight.  They are my preference in forends.  Assembling the weapon is satisfying and fun but some don't like to do the upper.  I actually have one of the lightest highest quality / reliability upper configurations that I might be willing to part with, but it is not a budget set up.   

aloha surf, could you describe the setup?

one of the lightest highest quality / reliability upper configurations that I might be willing to part with, but it is not a budget set up.   

If you are buying a stripped barrel, then your options are somewhat limited regarding the FSB.

Besides like you already mentioned, with the type of rail that you would like, it will most likely end behind the FSB.

Seems like a lo-pro gas block with a 12"-14" 1 piece FF modular rail would open up a lot more options for you.


For every build that I do, I create a build sheet. I use that to critique my build as well as a check off list. This helps me to visualize my build, and help reduce the chances of making too many mistakes.

aloha surf, could you describe the setup?

Sure.  I do a lot of builds which would be similar to the Noveske Shooting Team's NST uppers http://dsgarms.com/ProductInfo/NVU-16NST-556.aspx, however at times I may not choose a SS barrel option and I generally prefer a 16" midlength variant but will do 18" set ups for those who like the longer gas system in an intermediate or rifle length and I own an 18" LW intermediate also.  When doing 16 inchers or even 14.5's, I may also go with a lighter lightweight profile barrel by substituting a high quality Chrome Moly barrel that comes very close in accuracy but shaves a bit extra weight and is lower maintenance.

As an example one upper that I have right now which is new, including test fire for function, looks like this
- BCM16" midlength, 1:7, BFH, lightweight profile barrel
- BCM Low Pro gas block
- Noveske NSR 13.5" rail
- Colt Cerro Forge M4 flat top upper receiver
- Colt M16 full auto bolt carrier group
- BCM Gunfighter Charging handle (optional stock charging handle or Rainier Arms Raptor Ambi handle)
- SJC Titan Compensator (optional BCM comp, BattleComp or stock birdcage)

It isn't anything new, but it is a very high quality component, high reliability, extremely durable, excellent accuracy in a lightweight package.

mahalo surf

Sure.  I do a lot of builds which would be similar to the Noveske Shooting Team's NST uppers http://dsgarms.com/ProductInfo/NVU-16NST-556.aspx, however at times I may not choose a SS barrel option and I generally prefer a 16" midlength variant but will do 18" set ups for those who like the longer gas system in an intermediate or rifle length and I own an 18" LW intermediate also.  When doing 16 inchers or even 14.5's, I may also go with a lighter lightweight profile barrel by substituting a high quality Chrome Moly barrel that comes very close in accuracy but shaves a bit extra weight and is lower maintenance.

As an example one upper that I have right now which is new, including test fire for function, looks like this
- BCM16" midlength, 1:7, BFH, lightweight profile barrel
- BCM Low Pro gas block
- Noveske NSR 13.5" rail
- Colt Cerro Forge M4 flat top upper receiver
- Colt M16 full auto bolt carrier group
- BCM Gunfighter Charging handle (optional stock charging handle or Rainier Arms Raptor Ambi handle)
- SJC Titan Compensator (optional BCM comp, BattleComp or stock birdcage)

It isn't anything new, but it is a very high quality component, high reliability, extremely durable, excellent accuracy in a lightweight package.

I really like the midwest industries free float rail that Ku posted the link to.

It's light, comes with 3 small rail sections and QD sling mount, which all can be screwed directly to the rail via threaded holes from the outside.

It also mounts very solid.

I don't have any experience any others though.