I am thinking of putting together a new 20" upper using a MI 12" quadrail. I have never shot highpower before, but I think I might want to start. Are these quadrails legal for service rifle use? I don't plan on being a serious competitor, I just want to improve my skills. I did a google search and it seems that there is some disagreement on whether or not you can use this type for service rifles. This is the one I am looking at...

quad rail

Back when I was shooting local DCM Highpower matches with ARs the rifle had to be externally like the standard issue Service Rifle. That meant mil-spec muzzle to butt, i.e. M16-A2, 20 inch, carry handle upper etc. There may have been some cosmetic variances allowed,  but if so I never remember seeing any. And I surely do not remember seeing any Quadrails. It is possible, if not likely, that the rules have been eased to allow for more variations in appearance in light of the fact that there are different versions that are now recognized as "service rifles"  

Armalite has a very cool solution though. They use a barrel nut and tube system that free floats the barrel by mounting the forward hand guard cap on the end of the FF tube. This allows the use of the standard GI fore-end upper and lower halves while having the benefit of FF'ing.

HTH

I just screwed one together last night with a G2 MI free float rail. It's legal.

You need a way to attach the front sling though. MI sells a doohicky you can use.  

B

Geissele has the nice service rifle rail

Been legal for a few years now.

Keystone in Pennsylvania can machine a sling swivel installation for a number of different rail systems.

 

With the current draft of the 2016 Service rifle rules pretty much everything is going to be legal as long as its AR-15 based, 5.56, maximum 20" barrel, standard grip, fixed butt-plate and cheek piece. The rest, have at it.

Is the G2 worth the extra few bucks over the regular T series? Is it a more secure mount?

I keep going back and forth between the G2 and the regular.

I don't know anything about the T series. Looks like it just screws on to the barrel nut so you have to time it with a jam ring which is probably a little more fiddly than the G2. The G2 has a barrel nut with a long section that the float tube slips onto and it then clamped with two socket headed cap screws. There is actually a split in the tube right under the chamber, and the cap screws draw the two sides together and clamp the barrel nut. There are also teeth that index into the barrel nut to keep it from rotating. It's a little hokey.

It works. You are supposed to use some locktite on it to make sure it does not move. It's only 14 ounces too, so for a lighter build it's ok. I have another gun with a Geissele Mark 7 NM and that is a slick tube without any need to time the barrel nut. You time the handguard and that's it. It's much heavier though.

If the rules for SR end up being really screwed up, I'm probably going to use a Gen 3 from MI.

B

Here is my MI G2. Thought I had a pic of my MI sling stud on it.  It's located 6'o-clock on the first spot behind FSB. The scope is now on my 18 SBR. Love the set up with A4 carry handle.  I may put a 4 or 4.5 power scope on it later.


Edit for links:
MI gen2 two piece
MCTAR-07 sling stud

I just ordered my MI T series G2 yesterday. Now I just have to wait for all my parts to arrive in the mail.

I like the Larue thought there is a gap between the FSB and the rail end

The only downside with Quadrails is they are ( Quality ones ) more expensive than a $99 RRA DCM Free Float tube. If you are wanting to build from scratch optic sighted high power AR a standard DCM A4 is prob the best way to go.

What I did on mine ( spare 20 rifle I have with a quadrail ) for a forward sling swivel was bolt on a front M14 forward sling swivel. Hole pattern lined up perfect with rail cuts, width of M14 forward swivel is same width as rail top surface, swivel is farther forward in a more correct position..The aftermarket bolt on swivels are either cheap junk and or too expensive....

BRILLIANT!!!

I'm struggling with buying an RRA NM A$ upper and building a matching lower or using the spare KAC FF rifle length RAS I have and using that for the upper (or use it for a SAM-R build).  or both?

I've been out of the high power game for a while, but we used to have lead weights wrapped around the float tube under the handguards, did shooters quit doing that, or how are they done with quad rails?

I thought Geissele had weights you could screw on as rail covers or underneath their rail?
Yup. https://geissele.com/12-7-super-modular-rail-mk7-black.html