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Senior Member
What do you mean by "pop back to center"?Originally Posted by scottryan
Are you compressing the barrel and tube against each other or away from each other to the 9 and/or 3 o-clock positions, or are you saying you are twisting them against each other clock and counter-clock-wise, or what? I am a bit confused by what you mean.
Senior Member
I grab the end of the rail in one hand, and I grab the flash hider in the other and I pull them in opposite linear directions. A lesser rail will have the barrel not centered in the rail after I do this.
Sometimes I can do this with as little as hand pressure by squeezing the end of the barrel and rail with my hand.
I have done this with a 15" KMR (Maganese/Aluminum), Samson, Midwest Industries, and Armalite keymod rails. Shorter KMRs I can't seem to get enough leverage on them to be able to do this. I haven't tried a KMR Alpha 15" yet. The Armalite and Samson in particular were the worst.
Last edited by scottryan; 09-25-16 at 19:34.
"Not every thing on Earth requires an aftermarket upgrade." demigod/markm
Member
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
Member
To add...
When considering deflection, you would also need to consider, accuracy of your rifle, and accuracy of your ammunition, on a lower, with shooter in the loop.
Jim
Member
Funny, when I was trying to see if I could subjectively feel a difference in my various rails' flexibility (and thus rigidity/mounting system) the other day I decided that this wasn't a good way to test since the barrel flexed more than the rails did, and they all returned to center/concentric (KMR 13, KMR-A 15, URX4 14.5, and V7 Enlightened 15).
Grabbing the rail at the mounting point and applying pressure at the end to try and deflect it is a better way, but the SNR was too low to really conclude anything.
Member
In order to evaluate my own rails, I held the ARs in firing position and applied 3:00 and 9:00 pressure at the end of the rail while co-witnessing an Aimpoint dot and BUIS. I also attached a visible laser to the end of the rail and visualized the relationship of the Aimpoint and laser dots.
On the original KMR it was very easy for me to move the Aimpoint dot completely off the FSP.
The NSR and Troy Alpha performed about equally. They were both significantly stiffer than the KMR, but I could still get some movement in the dot in relation to the rail if I applied a lot of force. I was not however able to move the dot completely off the FSP.
On the Daniel Defense Lite/M4 and Geissele SMR rails I could not induce any noticeable shift.
As others have inferred, it is all cost/benefit. The KMR is great on a build where your objectives are to minimize weight, get your support hand out as far as possible for ergonomic purposes, prevent the barrel or fsp from burning you, and hang a sling. It is very comfortable to shoot with, and the weight savings is noticeable. It is not, however, probably the best choice if you really need an IR laser or BUIS to hold zero if the rail is loaded whether by a barricade, bipod, sling, or heavy manual pressure. I also have less faith in its ability to hold zero without cross-checking and periodic adjustment in the long-term.
I do however have a great deal of faith in the Geissele SMR or Daniel Defense Lite rails to maintain the information of the zero indefinitely with something like stowed MBUS Pros, but that comes at a cost of 4-5 ounces. Whether that cost is worth paying is personal and relative to application.
Senior Member
The barrel nut on the KMR is too short. It should be twice as long.
Look at a NSR or Giessele barrel nut. Bill Giessele even talks about this in one of his internet videos.
"Not every thing on Earth requires an aftermarket upgrade." demigod/markm
Senior Member
I believe the Wedgelock barrel nut is at least as long as the Geissele, but don't have the specifics in front of me.
Banned
Does anyone know of an adjustable gas block that would work with the Hodge rail?
Member
You could also go the adjustable BCG route. I tested my 2A Armament RBC this weekend and found it very easy to use. It also opened up operating spaces that I wasn't able to get using the SLR Sentry block I had on there before.
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