light weight rail or light weight barrel

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Lightweight rail unless you’re going to mount a heavy laser like the MAWL.

Why would a laser have anything to do with how heavy the handguard is?

[WobblyPossum]

Why would a laser have anything to do with how heavy the handguard is?

I’m guessing the thought process used is that heavier handguards are generally stiffer than the lightweight ones and should flex less. I don’t know if weight:stiffness is a 1:1 relationship in all cases. I think stiffness depends on more design elements than just the weight of the handguard.

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I’m guessing the thought process used is that heavier handguards are generally stiffer than the lightweight ones and should flex less. I don’t know if weight:stiffness is a 1:1 relationship in all cases. I think stiffness depends on more design elements than just the weight of the handguard.

Right, and @Bergeron said just as much in an earlier post. Having a heavy-ass handguard doesn't mean a handguard won't deflect, given that the barrel nut/handguard interface is also a huge element here; a super stiff tube is only part of the equation.

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Some thoughts from Jim Hodge:

Hey guys...hope all is well with all of you. I want to address rail and barrel deflection. First off in my observations, rail and barrel deflection can come from various sources. What is deflection, to me it's when a constant load is being placed on the rail, and how much it moves under a load. Why is deflection important to you....to me, it's in the use of aiming devices such as lasers etc. What causes deflection....here is where it gets sketchy....so your results may vary.

Type of fitment of rail onto barrel nut.
Type of barrel nut and how long, and how much bearing surface it has to the rail.
Upper receiver, how tight the barrel extension goes into the upper, concentricy of face of upper, threads, torque value, heat, demential mass in the upper, etc...can be variables.
Type of fitment between the lower and upper.

Basically if one were to test the "flexibility" in a rail not attached to a barrel/upper, you would not likely see much flexibility to make any real difference.

If you see barrel deflection under a rail load, it's the upper flexing via the threads the nut is attached to.

You have to ask yourself, what is important to you in the way you use your carbine, and how much difference does it really make? Not everyone runs lasers, not everyone loads a bipod, and will a sling and or a barricade effect you enough in a dynamic environment.

I have tested mine, as well as others, we did great, but yet there are others out there who did great as well.

There is no standardized testing that I know about... so yet another variable ��

DD, Geissele, KAC... I've used them all, and all with good results.

Cheers, Jim Hodge

Source: https://www.m4carbine.net/showthread...91#post2385691

[OlongJohnson]

If it has to be a choice between those two, go with the one with the Centurion rail. Better rail IMO since BCM's are still technically a form of a pinch lock.

What do you believe is wrong with a pinch lock? I think the BCM mounting system is pretty darn good, and have explained why in the past.

[Sig_Fiend]

What do you believe is wrong with a pinch lock? I think the BCM mounting system is pretty darn good, and have explained why in the past.

I'm talking more about bottom-mounted pinch lock style rails. Essentially a muffler clamp style. BCM's mounting system is definitely much better. It's still clamping a circle around a circle, with a rectangle (upper section and 1913 rail) on top that could theoretically deform if tightened too much. That's just a guess on my part, and I may be wrong. At the least, I'm sure BCM's method significantly reduces the likelihood of deformation. I mainly wish their barrel nut was longer and their handguards a larger diameter.

Maybe not all but, many pinch lock rails usually achieve tension via two pieces of the handguard bending, typically tabs on the underside. I'm not a fan of that and feel like it's inconsistent. The closer I can get to a consistent torque spec as opposed to going by feel, the more confident I'd feel about it.

With Centurion's C4 rails, although they're 2 piece and screw together, they're not a pinch lock per-se. The locking surfaces at the rear are simply flat pieces that screw together and don't really bend since its not needed due to the way the rear portion locks around a GI barrel nut.

[OlongJohnson]

I'm talking more about bottom-mounted pinch lock style rails. Essentially a muffler clamp style. BCM's mounting system is definitely much better. It's still clamping a circle around a circle, with a rectangle (upper section and 1913 rail) on top that could theoretically deform if tightened too much. That's just a guess on my part, and I may be wrong. At the least, I'm sure BCM's method significantly reduces the likelihood of deformation. I mainly wish their barrel nut was longer and their handguards a larger diameter.

The circle around a circle is bomber. It's the whole point that the rectangle section is where the flex happens. The square gas tube channel is able to be squeezed together when the screws are tightened, giving full tension contact of the rail all the way around the nut. The rails that pinch at the bottom are relying on this rectangle section to hold tension like a C-clamp, which is tough. They are going to open up, which bends the legs away from each other and distorts the circular part near the legs away from the round nut, reducing firmness of contact.

The only problem I've found is that when tightening, loosening, and tightening the BCM nut the three times, even using the right tool and being careful to keep it properly aligned so nothing slips, you can still raise a lump adjacent to the notches in the nut. That has to be filed or stoned back to round, or the handguard becomes difficult to install and the nice firm contact around the circle is disrupted.

The QRF is bigger and beefier than the MCMR rails, but I believe still smaller and lighter than some other quad-PIC rails.

[Sanch]

Why would a laser have anything to do with how heavy the handguard is?

Some issues with MAWL lasers causing lighter rails like Geiselle to bend. A Quad Rail will be less likely to bend than a light weight low profile rail that has 1/3 the weight of you put a heavy laser on it.

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Some issues with MAWL lasers causing lighter rails like Geiselle to bend. A Quad Rail will be less likely to bend than a light weight low profile rail that has 1/3 the weight of you put a heavy laser on it.

Yeah... no. A few extra ounces at the end of a handguard is not going cause any human perceptible shifts in structure of the handguard.

[theJanitor]

Some issues with MAWL lasers causing lighter rails like Geiselle to bend. A Quad Rail will be less likely to bend than a light weight low profile rail that has 1/3 the weight of you put a heavy laser on it.

Where are you seeing that bolting a laser to the front of a rail will "bend" it? I can get my laser to deflect a little, if I get the vfg on a wall and load up hard on the stock. Otherwise, at normal (for me, out to 100) distances, even that shift is super small. And if the laser is on IR, the shift is way less than I can see anyway. Note that I don't have a laser on a rifle with a bipod, nor do I load up a sling super hard as to deflect the laser, either. I'm using lasers on Geissele mk4, mk8, mk16.

But bolting a MAWL to the handguard will bend it?