URX 3.1 Rail Rigidity/General Rail Rigidity

HELLO P&S

I am currently buying parts for a rifle which I will eventually use with nods. Obviously it will be getting some kind of IR laser and the laser will need a rigid rail to sit on. I am unfortunately doing this build at a time when parts are somewhat limited in availability so I do need to use what I can find. One of the rails I've found still in stock is the urx 3.1, although the lack of material where kac removed the pic rail on the sides makes me suspect that it may not be the best option in terms of rigidity. Do any of you have any experience with the 3.1 while using nods and a laser? If so, did you experience any serious zero shift?

If it did not perform well, I would like everyone's suggestions on handguards that are capable of holding a laser zero.

Thank you guys very much for your help.
 

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Raven

Newbie
I don't have experience with that one, but I've had/seen good results with the various Geissele flavors, hodge S-lock, the various wedge lock rails, and the SLR HDX 7075. I run the SLR and the Hodge. The SLR is not as rigid but it is way lighter. Note I've had no issues with the SLR rail at all. For reference I'm using a MAWL.
 

bates

Newbie
I'll go test mine tonight

I've got the above rail on some 14.5's and 11.5 with lasers

I'm new to NV but so far they seem solid, i'll turn on the visible laser and see if it moves with pressure off a barricade
 
I don't have experience with that one, but I've had/seen good results with the various Geissele flavors, hodge S-lock, the various wedge lock rails, and the SLR HDX 7075. I run the SLR and the Hodge. The SLR is not as rigid but it is way lighter. Note I've had no issues with the SLR rail at all. For reference I'm using a MAWL.
Thanks for the info, Raven. Ive heard the hodge rails are sone of the best but even compared to the other out of stock stuff those are SUPER unobtanium. I did manage to get a hodge 14.5 from the last batch though:cool:. Im kindof spooked about geissele after the bendy bill thing, not sure if that fear is overblown i am literally a noob at this. I will check out slr, I have their gb7 gas block and its cool.

I'll go test mine tonight

I've got the above rail on some 14.5's and 11.5 with lasers

I'm new to NV but so far they seem solid, i'll turn on the visible laser and see if it moves with pressure off a barricade
Yooooo thank you bates, that is exactly the info I was looking for. I'll be here waiting for results!! And yeah I'd be getting the 13.5 inch one or whatever the longer one is so thatd be really useful info to me.
 
So I found some interesting info upon further research. Dude in this thread says that he was able to shift the zero on his laser by hitting his urx 3.1 with a dead blow.


I don't really know how applicable this is to actual use of a rifle. Id be more interested in tests like rail flex after drops from different heights and if there was any point of aim shift while applying pressure from barricade or sling or whatever. Or maybe I dont know anything about real life situations and a dead blow smack is a good simulation of actual use. Interesting to consider either way. I wonder how a ris ii or a urx 4 would fare in this type of test.
 

Nate Osborne

NateMac
Staff member
Moderator
So I found some interesting info upon further research. Dude in this thread says that he was able to shift the zero on his laser by hitting his urx 3.1 with a dead blow.



I don't really know how applicable this is to actual use of a rifle. Id be more interested in tests like rail flex after drops from different heights and if there was any point of aim shift while applying pressure from barricade or sling or whatever. Or maybe I dont know anything about real life situations and a dead blow smack is a good simulation of actual use. Interesting to consider either way. I wonder how a ris ii or a urx 4 would fare in this type of test.
I don't own any lasers, or night vision equipment. I do have a few rifles with a URX4. I might have to do a range session with @Matt Landfair and and do some deflection testing. One URX4-equipped upper has a decent magnified optic and bipod on it, it would be pretty easy to load the bipod and watch for deflection.
 

pointblank4445

Established
I don't own any lasers, or night vision equipment. I do have a few rifles with a URX4. I might have to do a range session with @Matt Landfair and and do some deflection testing. One URX4-equipped upper has a decent magnified optic and bipod on it, it would be pretty easy to load the bipod and watch for deflection.

That's always a thing in regards to the barrel/barrel nut/rail construction to some degree. The worst I've ever seen was when I stuck a proof barrel into a Hodge Mod 1 for a hot minute. Could make it walk like 9" at 100y with a moderate bipod load.
 

Nate Osborne

NateMac
Staff member
Moderator
That's always a thing in regards to the barrel/barrel nut/rail construction to some degree. The worst I've ever seen was when I stuck a proof barrel into a Hodge Mod 1 for a hot minute. Could make it walk like 9" at 100y with a moderate bipod load.
Yeah, you can get some pretty significant shift, although I have never seen that significant of a shift in person. If I remember right we tried an HK mr556 with a laser, and it was pretty resistant to shifting. With the URX4 being a single piece with no separate barrel nut, in theory it seems like a good candidate for mounting a laser.
 

Default.mp3

Established
Friend of mine has an LPR and does a bit of precision; when loading the bipod, he did get noticeable shift in POI.
 

Matt Landfair

Matt Six Actual
Staff member
Administrator
I don't own any lasers, or night vision equipment. I do have a few rifles with a URX4. I might have to do a range session with @Matt Landfair and and do some deflection testing. One URX4-equipped upper has a decent magnified optic and bipod on it, it would be pretty easy to load the bipod and watch for deflection.
I have lasers.
 

pointblank4445

Established
Fisher talked about this in a podcast once on zeroing off a bipod vs off a bag vs off a bench.

I've got some guns where it's fairly minor and if the load is consistent, you won't see shift if you zero'd off the bipod and are grouping the same way.

Nate, when you talk about the MR556 was it the OEM 9" quadrail? I used to have a 16.5" 416 with the M27 profile (so a little lighter than the MR556) that I could get some impact shift with an Atlas bipod and RAHG rail setup as a DMR...nothing like what I mention above, but it would open up group size. Not that I believe it much, but it's been said over on HKPro (so red flag) that some don't mount bipods forward the gas block a la the G28 handguard to reduce the amount of force that can be applied to the barrel/barrel nut.
 
So the absolute king Bates from earlier in this thread dm'd me the results of his experiment with the 13.5 urx 3.1 and the 10.75, results were as follows:

Ok

so I took them out

can you make the 13.5 flex

oh yeah you can

not a ton but with a god amount of weight using down on the rail it will move but it really takes a lot of pressure to do so

the 10.75 was much more solid

didn’t move much if any

under normal shooting I don’t see either being a problem

I don’t feel with a 223 that you would ever need to load up enough to cause flex
I’d probably just get a hodge and be done if it’s a dedicated night gun and go shorter than 14.5
Sounds like the 13.5 isnt the best option but would do in a pinch, so Im not sure what Im gonna do. I'm not in a huuuuge hurry to complete this build so I may wait around and see if I can find a urx 4 in stock or for sale anywhere. I know I could get a ris ii or whatever but $450 is steeeeep for a rail. Ideally I would find a hodge but we all know the deal with hodge part availability so it is what it is.

I don't own any lasers, or night vision equipment. I do have a few rifles with a URX4. I might have to do a range session with @Matt Landfair and and do some deflection testing. One URX4-equipped upper has a decent magnified optic and bipod on it, it would be pretty easy to load the bipod and watch for deflection.
Thanks for this info nate, I would be very interested in the results from these tests. Really I'd love to know more from anybody with any type of rail. When you get around to doing this if you could drop the results in this thread or dm me I would really appreciate it!!
 

Default.mp3

Established
There are plenty of DD handguards that don't cost that much. Same with Geissele (especially the older ones, which are known to not suffer from the same issues as the MK16) and even ALG handguards. Beyond that, there's also the question of length handguard you even run; big difference between a 9" and 15" handguard in how much deflection you can generate realistically, particularly if it's just off the sling, barrier stop, or WML. Handguards like the Griffin Armament Low-Pro-RIGID and Centurion Arms CMR have very stiff tubes, too, though I'm not sure of their barrel nut interface. Heck, same thing can be said about any handguard that's designed to be compatible with suppressors being tucked into them, just by virtue of basic physics (bigger tube, stiffer tube).

As for needing a laser for testing:
Jack Leuba said:
All of these things can be easily verified by the individual user without firing a shot. Just put a red dot sight on the end of the handguard 12:00 rail and rezero the dot so that when you look through your primary sighting device it is in a hard reference location to the reticle. A decent mid-range magnification optic that allows you to match parallax between the two and has some kind of measurement reference in the reticle is really good for this application, though most LPVOs and red-dots will have a 200 yard fixed parallax. Just apply different pressure to the handguard, and see where the dot goes, and by how much. You can also smack the handguard with a dead-blow hammer and see what happens. If you want to get really weird, rest just the barrel on a table and look at how much shift happens naturally in the gun when it's in your hands that you never thought to think about.
 
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