DD vs. LaRue rotation potential

[Singlestack Wonder]

I'm getting ready to purchase a FF rail system for my CAR15. I have extensively researched most major manufacturers and have finalized my selection on either a Larue or Daniel Defense.

The Larue system features a "Keeper" that has a detent slot that fits the riser on the receiver frame, thereby eliminating any chance of rotation.

Daniel Defense's system has a free float collar that sits behind the barrel nut (remains loose when the barrel nut is tightened) and when bolted to the handrail, allows for a "pinch" fit (the free float coller and the rail pull together to clamp on the barrel nut).

Mechanically, the Larue seems to add that extra level of rotation prevention.

Your opinions?

[Robb Jensen]

Both if properly assembled will never come lose on their own.

[RAM Engineer]

Sorry to hijack, but I've got a question about these two rails also, and GotM4 is just the guy to answer it:

Between the Larue rails and the DD Lite Rails, which would require a shaved FSB to be cut down THE LEAST?

[Robb Jensen]

Sorry to hijack, but I've got a question about these two rails also, and GotM4 is just the guy to answer it:

Between the Larue rails and the DD Lite Rails, which would require a shaved FSB to be cut down THE LEAST?

They require about the same amount of removal of metal on the FSBs.
I do my 'ultra-low' and it fits great under both. The top area under both rails is the tightest area.

Ultra-low is the one on the right in these two pics:

http://img.photobucket.com/albums/v408/gotm4/barrel%20work/shavedFSBs003.jpg
http://img.photobucket.com/albums/v408/gotm4/barrel%20work/shavedFSBs004.jpg

[spamsammich]

If you're absolutely convinced that you'll be able to rotate a DD rail, check out their RIS II rails. They have the same type of bolt up locking system as the Lites but have location tabs milled into the back of the lock up ring to keep it from rotating. But gotm4 is right, once properly installed, they go nowhere without SERIOUS torque applied to them.

[Singlestack Wonder]

Is it safe to say that each gas block is unique with respect to the drilling of the taper pin holes in the front sight gas block and the barrel (i.e. it's not a precision, mass produced step done on an automated CNC setup), and if so, one cannot take a bucket of DPMS drilled barrels and front sight gas blocks and start mixing and matching them?

[Robb Jensen]

Is it safe to say that each gas block is unique with respect to the drilling of the taper pin holes in the front sight gas block and the barrel (i.e. it's not a precision, mass produced step done on an automated CNC setup), and if so, one cannot take a bucket of DPMS drilled barrels and front sight gas blocks and start mixing and matching them?

Sometimes if things are manufactured close to the same date by the same manufacturer a different FSB will work , but not always. Each is unique.

[SWATcop556]

I can not speak for the DD Rails but all three of my Larue rails are still in the same place since the first day I installed them. No rotation what-so-ever and that is after some heavy heavy heavy use!

[Singlestack Wonder]

Thanks for your opinions!

[Pistola]

I have a DD lite rail on mine even with the VFG. As long as the instructions are followed on the placement of the bolts, that thing ain't going nowhere.

[BravoCompanyUSA]

They require about the same amount of removal of metal on the FSBs.
I do my 'ultra-low' and it fits great under both. The top area under both rails is the tightest area.

Ultra-low is the one on the right in these two pics:

http://img.photobucket.com/albums/v408/gotm4/barrel%20work/shavedFSBs003.jpg
http://img.photobucket.com/albums/v408/gotm4/barrel%20work/shavedFSBs004.jpg

Wow!
Very Nice Work.

[Robb Jensen]

Wow!
Very Nice Work.

Thanks! :D

[Singlestack Wonder]

I have a DD lite rail on mine even with the VFG. As long as the instructions are followed on the placement of the bolts, that thing ain't going nowhere.

True...........provided that enough torgue to loosen the barrel nut is not applied. :)

[RAM Engineer]

I would think the bolts on the Lite rail would work just like the anti-rotation tabs on the Larue or the Troys.

[spamsammich]

I would think the bolts on the Lite rail would work just like the anti-rotation tabs on the Larue or the Troys.

They don't. They aren't close enough to the upper receiver to act as an index or rotation limiter. they could to some extent, but nobody would put up with that much rotation.

[mark5pt56]

I've seen both systems run into the thousands of rounds with no issues. As GotM4 stated, properly installed and it won't loosen.

[Singlestack Wonder]

I've seen both systems run into the thousands of rounds with no issues. As GotM4 stated, properly installed and it won't loosen.

Unless I'm missing something, the Daniel Defense Lite Rail is attached entirely to the barrel nut. If the barrel nut should rotate, so does the rail. The DD RIS II, Larue,, and Troy, systems have anti rotation devices that "hug" the sides of the receiver that would prevent too much rotational torque being applied to the barrel nut. This seems like an important detail Daniel Defense missed on the Lite Rail series (is the M4 Series also supported by the barrel nut only too?).

[mark5pt56]

Unless I'm missing something, the Daniel Defense Lite Rail is attached entirely to the barrel nut. If the barrel nut should rotate, so does the rail. The DD RIS II, Larue,, and Troy, systems have anti rotation devices that "hug" the sides of the receiver that would prevent too much rotational torque being applied to the barrel nut. These seems like an important detail Daniel Defense missed on the Lite Rail series (is the M4 Series also supported by the barrel nut only too?).


This is a pic from the ADC piston upper that I logged 6000 hard rounds-I mean hard rounds through. It never moved and I doubt it ever would. It got pretty hot numerous times and that excess heat and cooling along with hard use did not cause anything to loosen. My advice is to pick the one you want and don't worry about it.
In my opinion, alot of people concern themselves about things they will never subject a weapon to. If you are shooting that much, you more than likely are given the ammo/weapon or have enough funds to have a great replacement/maintenance program.

Mark

buy the way-the dat is wrong in the pic

http://img.photobucket.com/albums/v509/mark5pt56/100_2617.jpg

[spamsammich]

I've said it before and I'll say it again. If you can generate greater than 65 ft-lbs with just your bare hands and move a properly installed Lite Rail, you must have silverback gorilla-like strength. Yes a better lock up ring is a detail I would like to see them improve on, I also recommended that they knurl the barrel nut to give a little more bite. But so far I haven't had a 14", 12", or 10" rail move at all and believe me, I've tried to get them to move by reefing on my VFG to gain some lever arm. I'm not going to sweat it until something happens. Don't wanna listen to people that own them or a guy that has probably installed hundreds of them? That's cool too.

FYI unless something has changed since I last saw them, the DD M4 rails do not have a Larue like anti-rotation system. They do have alignment pins that index the rail to the barrel nut.