DDM4/SLiM rail anti-rotation problem?

[justin_247]

I was just watching this video review of a DD rifle with the SLiM rail from AK Operators Union on YouTube, and at 1:25 you can see where the rail rotated slightly, maxing out the anti-rotation tabs.

https://youtu.be/QQOa5B_66oY?t=1m25s

This is one of the things I was wondering about after I installed my DDM4 rail, since the anti-rotation tabs aren't actually "fit" to the receiver and allow some play if sufficient force was applied. This is a problem if you are shooting with BUIS (which I do, occasionally). Additionally, the barrel nut is smooth with no knurling, with the rail is attached to the nut simply by a plate behind the nut that screwed into the rail... without anything providing additional friction to prevent it from rotating. Without knurling, I can definitely see how the rail could rotate on the nut.

In addition to the problems this would generate for your BUIS' zero, the tight tolerances inside the rail could also cause the rail to no longer be truly free floated, since the rail may contact the gas block. I have a BCM lo-pro gas block under my rail, and it wouldn't take much rotation for the rail to touch it.

And, if you make the ill-advised decision to bridge the gap between the receiver and the rail with your scope mount, this could cause the scope to be thrown off zero, as well.

BCM's anti-rotation solution seems superior here, in that the tabs are actually more "fitted" to the upper receiver. But I don't know how tough they are, so don't take my word for this.

Honestly, I don't think this would affect function and I'm not going to swap out my rail anytime soon, but, in retrospect, I probably should have purchased a rail that allowed me to keep my front sight post. This post is NOT a dig at DD, and I will continue to purchase DD products in the future with confidence. BUT, if you shoot with BUIS from time to time, I definitely encourage you to keep your FSP.

This post is NOT a dig at DD. If you want to attack DD, go elsewhere.

[Mrgunsngear]

I was just watching this video review of a DD rifle with the SLiM rail from AK Operators Union on YouTube, and at 1:25 you can see where the rail rotated slightly, maxing out the anti-rotation tabs.

https://youtu.be/QQOa5B_66oY?t=1m25s

This is one of the things I was wondering about after I installed my DDM4 rail, since the anti-rotation tabs aren't actually "fit" to the receiver and allow some play if sufficient force was applied. This is a problem if you are shooting with BUIS (which I do, occasionally). Additionally, the barrel nut is smooth with no knurling, with the rail is attached to the nut simply by a plate behind the nut that screwed into the rail... without anything providing additional friction to prevent it from rotating. Without knurling, I can definitely see how the rail could rotate on the nut.

In addition to the problems this would generate for your BUIS' zero, the tight tolerances inside the rail could also cause the rail to no longer be truly free floated, since the rail may contact the gas block. I have a BCM lo-pro gas block under my rail, and it wouldn't take much rotation for the rail to touch it.

And, if you make the ill-advised decision to bridge the gap between the receiver and the rail with your scope mount, this could cause the scope to be thrown off zero, as well.

BCM's anti-rotation solution seems superior here, in that the tabs are actually more "fitted" to the upper receiver. But I don't know how tough they are, so don't take my word for this.

Honestly, I don't think this would affect function and I'm not going to swap out my rail anytime soon, but, in retrospect, I probably should have purchased a rail that allowed me to keep my front sight post. This post is NOT a dig at DD, and I will continue to purchase DD products in the future with confidence. BUT, if you shoot with BUIS from time to time, I definitely encourage you to keep your FSP.

This post is NOT a dig at DD. If you want to attack DD, go elsewhere.

Embed:

[awdxtc]

10,000 rounds through my V5 and it's has not shifted at all.

[Wolfpack45]

Any properly installed, properly torqued rail system should not shift without serious abuse.

[Rob Ski]

I was just watching this video review of a DD rifle with the SLiM rail from AK Operators Union on YouTube, and at 1:25 you can see where the rail rotated slightly, maxing out the anti-rotation tabs.

https://youtu.be/QQOa5B_66oY?t=1m25s

This is one of the things I was wondering about after I installed my DDM4 rail, since the anti-rotation tabs aren't actually "fit" to the receiver and allow some play if sufficient force was applied. This is a problem if you are shooting with BUIS (which I do, occasionally). Additionally, the barrel nut is smooth with no knurling, with the rail is attached to the nut simply by a plate behind the nut that screwed into the rail... without anything providing additional friction to prevent it from rotating. Without knurling, I can definitely see how the rail could rotate on the nut.

In addition to the problems this would generate for your BUIS' zero, the tight tolerances inside the rail could also cause the rail to no longer be truly free floated, since the rail may contact the gas block. I have a BCM lo-pro gas block under my rail, and it wouldn't take much rotation for the rail to touch it.

And, if you make the ill-advised decision to bridge the gap between the receiver and the rail with your scope mount, this could cause the scope to be thrown off zero, as well.

BCM's anti-rotation solution seems superior here, in that the tabs are actually more "fitted" to the upper receiver. But I don't know how tough they are, so don't take my word for this.

Honestly, I don't think this would affect function and I'm not going to swap out my rail anytime soon, but, in retrospect, I probably should have purchased a rail that allowed me to keep my front sight post. This post is NOT a dig at DD, and I will continue to purchase DD products in the future with confidence. BUT, if you shoot with BUIS from time to time, I definitely encourage you to keep your FSP.

This post is NOT a dig at DD. If you want to attack DD, go elsewhere.

Agreed in 100%. I was honestly surprised by what happened. I was expecting more damage to the rail itself - obviously that didn't happen, rail took a beating very well. However rail shift was real and it would totally screw your iron sights zero.
I'm finally back home today so i could take rifle apart and check what happened. Both screws on the right side were lose, also upper screw on the left side was lose as well.
Lower bottom screw was still sitting extremely tight, but that didn't matter, since the whole "ring" shifted anyhow.
I have used now blue loctite - we will see if this will hold rail in place...

[Arch]

I've always used blue thread locker, and haven't had any rotation problems with my DD SlimRail 12.0 or Lite Rail III 12.0. In fact, I shot my LRIII again today at lunch (also taken to the range Thursday and yesterday). No appreciable rotation or concern.


I did have issues with my (now sold) DD MFR 12.0. I had to remove the MFR and reinstall (while re-loctiting and exceeding the recommended torque on each screw). This seems to have fixed the problem, but I probably only ran another 500 rounds through the Colt with the reinstalled tube prior to selling the whole rig.

[Nocalsocal]

Robski was the rifle purchased as a whole or put together? As in the rail was installed by someone other than Daniel Defense. If so I would be annoyed that it left the manufacturer that way. After all it doesn't really qualify as a budget rifle.

Sent from my SM-G935V using Tapatalk

[Arch]

The MFR uses a completely different locking arrangement so it isn't relevant to SR concerns:

IMG_3442_zpswor6h8fb.jpg

[Rob Ski]

Robski was the rifle purchased as a whole or put together? As in the rail was installed by someone other than Daniel Defense. If so I would be annoyed that it left the manufacturer that way. After all it doesn't really qualify as a budget rifle.

Sent from my SM-G935V using Tapatalk

Rifle was purchased as a whole. No mods were done to it, other than adding optics or iron sights.

I guess lesson here is, every time you have new rifle, no matter who the manufacturer is, just take it apart and tight all the screws by yourself.

[XM15M4Guy]

Hope to hear something from DD soon...