Rail deflection with MFAL's.

[danieljmaunder]

So I'm building a gun specifically for IR and NVG use, got a lot of night hunts and pest control planned for this year. I'm familiar with the issue of rail deflection especially with MFAL,s and want a really solid rail to mount the laser on. Outside of going with a monolithic design, what is one of the best rails to use as a laser host? The Daniel Defense RIS 2's seem to do well but I'd prefer to go with something a little lighter. I've tested some of the rails I have laying around, for example a forward controls RHF I can put a half inch of flex with my thumb and index finger on the muzzle device. Looking for mlok rails if possible that won't have a crazy poa/poi shift. Has anyone had any experiencd with the centurion CMR rails? The ones I've handled seem to be a little thicker than most other mlok rails

[gunnerblue]

Larue followed by Geissele (original, MK 2, 4 AND 8) for minimal shift. I'm sure that there are others but these two are all that I've used. Or, like you said, there's always monolothic.

[danieljmaunder]

I'd love a monolithic like an LMT MRP but damn they're expensive. Just can't afford the whole thing versus upgrading the rail on my existing upper.

[Defaultmp3]

Older post:

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

I doubt that the Centurion Arms AR-15 handguards would do particularly well compared to others on the market when it comes to deflection, given the small size of the barrel nut, though this is purely a SWAG and not something I know for a fact. Quad rail handguards might be rigid as **** given all the material on them, but they can still deflect if their interface with the barrel nut gives them room to move.

My question is, what kind of shooting hunting are you doing while hunting? Handguard deflection (obligatory screed about how handguards are not the same as rails, handguards can have rails, but you can also have just rail sections, etc.) is a real thing, but if you're mostly shooting off hand, or with minimal pressure on the handguard, i.e., you're not bearing down on the handguard to form stability like one would with sling-assisted shooting, barricade shooting, or loading a bipod, then it probably doesn't matter very much. Just resting your handguard on something should have pretty minimal POA/POI shift. Beyond that, if you're not using the rifle in a duty manner, then it's not a big deal to simply mount the pointer much further back on the handguard, which will minimize perceived deflection.

Otherwise, I would suggest looking at the various Hodge designs (WedgeLock variant, P-Lock, S-Lock, Drive Lock), Geissele (the older models having better rigidity than the newer models, e.g., MK8 vs MK16), Daniel Defense RIS (the III is coming out soon, you could always wait for that), Ripcord Industries LDR1, Griffin Industries RIGID series, Midwest Industries Night Fighter, and KAC URX4. Not an exhaustive list, and I do not personally vouch for anything on this list, just models to consider (I use a Hodge WedgeLock on my 11.5" that is my night gun).

[vandal5]

No experience with them but how about one of these?

https://www.ripcordindustries.com/ldr-1

[danieljmaunder]

There will be a lot of bipod or offhand with sling shooting which is why I'm concerned about flex. I know the DD rails are freakin solid and I saw the RIS 3 is about to drop so I might be interested in that. Beyond that, this will double as a go to rifle for whatever hypothetical situation we can invent in our minds so I have duty thoughts in this as well and definitely want the laser mounted as far forward as possible. Plus I just hate having shadow in the illuminator.

[Defaultmp3]

There will be a lot of bipod or offhand with sling shooting which is why I'm concerned about flex. I know the DD rails are freakin solid and I saw the RIS 3 is about to drop so I might be interested in that. Beyond that, this will double as a go to rifle for whatever hypothetical situation we can invent in our minds so I have duty thoughts in this as well and definitely want the laser mounted as far forward as possible. Plus I just hate having shadow in the illuminator.

With the force behind loading a bipod, you will likely see deflection with any non-monolithic handguard, particularly if it's a longer handguard. I would also be wary of any POA/POI shifts that can occur in such a situation, even without a pointer in the mix; a friend of mine was able to consistently generate several MOA worth of shift when he loaded the bipod on his KAC LPR. While stiffer handguards will have less deflection, that doesn't mean they will have no deflection; this is something that I was taught during my NODs class, the need to recognize when one was missing despite having a good sight picture and good trigger squeeze, and that deflection may be an issue, given the amount of force one can lever into a handguard, something that the instructor (Pressburg) had seen downrange.

I'm also mildly curious as to the use-case of regularly using a bipoded rifle with a pointer, rather than using a clip-on, if that level of precision will be needed.

[danieljmaunder]

Main reason for bipod use will be for some coyote stuff out of the bed of a truck, working on getting clip on sights but just dont have them yet. The bipod isn't as big of a concern as I'm well aware of how much force is generated when loading a bipod. But bracing off of a truck or using a sling to stabilize is what will be happening most of the time so I want to make sure that those forces aren't going to create a huge shift. The RIS 2 is probably the safest bet, as its proven and can double in a duty roll

[opngrnd]

The RHF handguard has much more shift than the DD and Geissele rails I've used. It's kind of like comparing the most flex to the least flex outside of going monolithic. The BCM rails also flex quite a bit. I'd take a good look at the available G and DD rails and go from there. Midwest Industries makes a series of rails for this application which you can find at the following link: https://www.midwestindustriesinc.com...ards-s/602.htm

[danieljmaunder]

Saw the nightfighter handguards and they look pretty good. You know anyone who's used them?