Quoted: Quoted: Grenadier Precision ARM-R (buy through LWRC), KAC's URX, YHM FF, POF Predator. I've got one of those already - not sure I'd mount a scope on it. To be honest, I like it so far - I really do - but I'm still not sure I'd use it for optics.

Agree. YHM = bad idea for lasers and optics IMHO.


C4

Don't forget the new VLTOR CASV-EL system. I just got them in and they are much better than the ARMS SIR IMHO. The only down side is that I cannot co-witness my EOTech on them.


C4

Here it is, any FF rail system that employ a lock ring to secure the rail to the barrel nut, those are suitable for optic mounting but..... but the chance the lock ring slipping and cause the rail to loosen and a zero shift is possible and that possibility is something no professional will want to live with. That being said, the only free float rail using this method that will work is the LaRue Rail, which has two screw that secure the lock ring and barrel nut once you get it indexed. example of this kind of system, KAC FF RAS, PRI, LaRue, Daniel Defense, and YHM

Rail system such as POF, KAC RAS2, ARMS SIR and Vltor adds a rail on top of a rail, that just screws up your mounting capabilities. RAS2 has just a hump but it also limit the way you can mount optics. Vltor is the best of the bunch, lower rail on rail height and light weight. POF having the highest rail on rial height, ARMS SIR is basically carry on a fight from a RAS era design, but I know Dick is probably got something up his sleeves with the SOPMOD2 contract...

there is the continuous rail system like the LW, Troy, LMT MRP, and KAC URX2. LMT is the best of the class, the best of any class since it is a monolithic rail platform, it does not shift, nor loosen. and the continuous rail concept is the wave of the future... mount your optic anywhere on your upper rail and you will not have a problem. KAC URX2 is new and use a special tool for installation, but once it is mounted, it is solid as a rock, I would be hard pressed to see the darn thing move. another great design but the down side is the rail will require special tools for installation, not a common man do it yourself item. Troy, Samson, LW rails bolt onto the standard barrel nut, they are solid but not as solid as the URX or MRP, they have one common problem, it has to bolt to the barrel nut which some times are not exactly in spec.. you will find installing the rail to be a problem if your barrel nut are out of spec.

remember mounting optic up front also adds weight, shift your weapon balance, it is cool and different looking but try to handle one of those suckers through a whole week of training, you will fast move the optic back to the center line. The advantage will not out weight the weapon balance issue. I find the optic is best on the front of the receiver give the weapon the best balance

so if any... LMT MRP, URX2, Rail on rail like the SIR, Troy style system, and LaRue....

Quoted: Here it is, any FF rail system that employ a lock ring to secure the rail to the barrel nut, those are suitable for optic mounting but..... but the chance the lock ring slipping and cause the rail to loosen and a zero shift is possible and that possibility is something no professional will want to live with. That being said, the only free float rail using this method that will work is the LaRue Rail, which has two screw that secure the lock ring and barrel nut once you get it indexed. example of this kind of system, KAC FF RAS, PRI, LaRue, Daniel Defense, and YHM Rail system such as POF, KAC RAS2, ARMS SIR and Vltor adds a rail on top of a rail, that just screws up your mounting capabilities. RAS2 has just a hump but it also limit the way you can mount optics. Vltor is the best of the bunch, lower rail on rail height and light weight. POF having the highest rail on rial height, ARMS SIR is basically carry on a fight from a RAS era design, but I know Dick is probably got something up his sleeves with the SOPMOD2 contract... there is the continuous rail system like the LW, Troy, LMT MRP, and KAC URX2. LMT is the best of the class, the best of any class since it is a monolithic rail platform, it does not shift, nor loosen. and the continuous rail concept is the wave of the future... mount your optic anywhere on your upper rail and you will not have a problem. KAC URX2 is new and use a special tool for installation, but once it is mounted, it is solid as a rock, I would be hard pressed to see the darn thing move. another great design but the down side is the rail will require special tools for installation, not a common man do it yourself item. Troy, Samson, LW rails bolt onto the standard barrel nut, they are solid but not as solid as the URX or MRP, they have one common problem, it has to bolt to the barrel nut which some times are not exactly in spec.. you will find installing the rail to be a problem if your barrel nut are out of spec. remember mounting optic up front also adds weight, shift your weapon balance, it is cool and different looking but try to handle one of those suckers through a whole week of training, you will fast move the optic back to the center line. The advantage will not out weight the weapon balance issue. I find the optic is best on the front of the receiver give the weapon the best balance

Good post Chen.



C4

Add in the ARMS unobtanium receiver level height SIR (is that more specific than same plane ...)

So on my list

KAC URXII
KAC RASII
KAC FF RAS AND MRE (albiet no handguard ring lock)
(*I've mounted an optic with one part of the scope mount - ARMS#35 - on the reciever and the other on the SR25 RAS, no concern)

ARMS SIR (all flavours)

DD AR10 (locking nut)
DD RAS (no handguard ring lock)

Larue

LMT MRP

L-W MRS (if/when)

HK 416 rail

Grenadier is LW Piston rail.

Quoted: Maybe by the time I make my mind up exactly what I want, the LMT MRP will be down to a reasonable price, and I'll just go that route.....

Don't count on it, LMT invest a lot of money to make the fixtures to build the MRP, and the process is very involving.  I think the price is reasonable for the amount of work involved.

I always get a little chuckle when threads like these come up.

Let's go back to the reason why free float tubes were invented in the first place.

It was found that when pressure was placed on the handguard, the barrel flexed and changed point of impact when you used a receiver mounted optic.
So, the free float tube was invented so that it could take the pressure of a sling-up or a bipod, and even if it flexed, it didn't affect the barrel or the point of aim.

Now, we have people wanting to put optics on the item which is going to flex, because it is only anchored at one end. As such, it is defeating the entire reason for a free float tube.

By putting the optic on a free float tube, you return the situation to an inverse of the original, where the optic will now move, and the barrel will remain unmoved, when pressure is applied with a sling or bipod, or rest.  Same thing with this cockamamie idea of putting front sights on the handguards.

I know some people think that their FF tube is soooo good that it can't flex. Keep telling yourself that.

Scopes belong on receivers. FF tubes are for taking pressure, and leaving the barrel unmoved. They are not for mounting sights.

Look, I'm all for making your gun look cool.
Just don't screw up the function with "cool" dress-up ideas.
If your accuracy requirements are very non-demanding, then you can do anything you want, because if you aren't concerned about hitting anything smaller than a barn door, there's no need to worry about it.


Sure, some are better at being rigid than others are.

Just re-read my post, and it was probably a bit more harsh sounding than I really intended.

I apologize if any offense was taken from it.

All I wanted to do was point out that I think the sights should be supported on a surface that is not going to move.

Quoted: What about the TDI X6 , from TDI Arms . I got a look at the system at a gun show last weekend .  It grips the barrel nut and the FSB . I tried to flex the one they had mounted on a dummy AR , and I couldn’t flex it at all with the VFG they had mounted to it . They wanted $250 for it , with the rail covers but didn’t have any carbine length left , or I would have bought one to try . I still plan to get one , but it isn't high priority at the moment since I have other goodies pending

Get a Surefire, cheaper and better design.... for a non-free float style RAS.

Quoted: Quoted: Quoted: What about the TDI X6 , from TDI Arms . Get a Surefire, cheaper and better design.... for a non-free float style RAS. I have a Surefire already . which is why I would like to try the TDI and price really isn't an issue .

I would look at the MI rail LONG before I looked at the TDI rail.

C4

Actually my barrel would flex before my rail will.  the deflection rate is so small on the rail flexing, it will still be combat accurate out to 300m with a red dot.

the way MRP, LaRue, URX are desinged, the rail can take a lot of pounding and it will stay true.  flexing is very min. and you would be hard pressed to find the optic loosing zero.

I have RAS with Reflex mounted up front that made good shot to 300m with me pulling on the sling to tighten my stances.  of course later i remove the optic to the receiver because i find the balance to be better suited for me with the optic on the receiver.

Quoted: Quoted: I would look at the MI rail LONG before I looked at the TDI rail. C4 MI ????

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C4