VLTOR MUR-1A and DD RIS II compatibility issue.

[Sebben]

So I have done quite a bit of digging and haven't found much of an answer. Because I really don't think anyone knows if the DD MK 18 RIS II rail system works with the VLTOR MUR-1A. Now I say the 1A because that was the whole point of this receiver is to accept a wider variety of rail systems using the relief cut on the front of the receiver. The same thing goes for the Rainier arms ultra match uppers. From my understanding the changes to both receivers was to accommodate the rail systems that use bolt up systems. So I went and got both the MK18 rail and MUR-1A. I checked to see if they fit and they COULD fit with damage to the upper and possible damage to the threads on the rail. The problem is that while screwing on the rial the screw heads dig into the upper. I tried to call DD and VLTOR earlier today and I don't think they are taking calls due to the overwhelming volume of them. So looks like I'm on my own! Hoping to get some useful input on here.

Here is where the screw digs into the receiver.

If you look on the other side it is much thicker at the top than the ejection port side. I don't think I can get the screw in with out cross threading the rail.

 

[buckjay]

Re: VLTOR MUR-1A and DD RIS II compatibility issue.

EDIT: Nm, jumped the gun!

I haven't seen that before. Its possible the upper OR rail may be slightly out of spec as I know Vltor redesigned the upper receiver specifically to work with the likes of the DD rails. I also had a Vltor MUR + DD RIS II upper receiver and it had no such issue.

I've had some DD rails with out of spec barrel nuts/collars so its entirely possible.

 

[SDWhirlwind]

Re: VLTOR MUR-1A and DD RIS II compatibility issue.

The first MUR's were billet and some of the first ones would not accept certain rail systems, I think DD was one of those. They changed to forged uppers that would. Yours pictured is one of the first billet uppers with the hump/bump on the left side that goes clear to the front. Find a pic of a new MUR and you will see the hump/bump is back 1/2" or so from front left. If that makes sense.

 

[Sebben]

Re: VLTOR MUR-1A and DD RIS II compatibility issue.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: SDWhirlwind</div><div class="ubbcode-body">The first MUR's were billet and some of the first ones would not accept certain rail systems, I think DD was one of those. They changed to forged uppers that would. Yours pictured is one of the first billet uppers with the hump/bump on the left side that goes clear to the front. Find a pic of a new MUR and you will see the hump/bump is back 1/2" or so from front left. If that makes sense. </div></div>

are you sure? The one i have is the new MUR-1A. the MUR-1 has the material that comes all the way to the front of the receiver on both sides such as this.

 

[SDWhirlwind]

Re: VLTOR MUR-1A and DD RIS II compatibility issue.

Sorry got my pics mixed up with my getting forgettfull brain.

You are correct that your first pic is the later version and bottom pic you posted is the first billet version! The first version is wider at mid point where the raised line goes down the center and is almost .2 wider at the bottom where it sets on the lower.

I remember reading that the change from the first model because of an issue with mounting a couple different rail setups?

Also thought both models were "A" only to mean 'assist'???

Again, sorry for typing instead of looking to confirm what I was typing the first time!

 

[Sebben]

Re: VLTOR MUR-1A and DD RIS II compatibility issue.

I'm thinking about giving the guys up at accurate ordnance a challenge LOL. It is possible to machine out short channels in the receiver to allow the screws to be screwed in. Then cerakote my receivers. Later I will need to cut the first rail section off the MK18 rail to accommodate the Noveske SB. It looks really nice once it's done.

 

[buckjay]

Re: VLTOR MUR-1A and DD RIS II compatibility issue.

I would wait for a response from DD first. I've had out of spec collars for the RIS and barrel nuts that did not line up with their wrenches. Its entirely possible something very simple is off

 

[johnson]

Re: VLTOR MUR-1A and DD RIS II compatibility issue.

You have to install the bolts through the barrel nut side BEFORE you attach the rail. After you get the threads started you then need to tighten each side a few turns at a time to tighten the gap. It's a PITA but the RIS II is worth the trouble.

edit: I have the MUR-1A with DD MK18.

 

[Sebben]

Re: VLTOR MUR-1A and DD RIS II compatibility issue.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: johnson</div><div class="ubbcode-body">You have to install the bolts through the barrel nut side BEFORE you attach the rail. After you get the threads started you then need to tighten each side a few turns at a time to tighten the gap. It's a PITA but the RIS II is worth the trouble.

edit: I have the MUR-1A with DD MK18.

</div></div>

LOL looks like im breaking out the sharpie! Or is there anything that can cover up that ding i put in the receiver?

 

[redirt78]

Re: VLTOR MUR-1A and DD RIS II compatibility issue.

Aluma-black. $10 from Brownells for a 3oz bottle. Heat the part up then apply liquid with a small paint brush or q-tip. A lot better than a sharpie.


I think you will like that combo, I have the same upper with a 14" DD Lite rail

 

[Sebben]

Re: VLTOR MUR-1A and DD RIS II compatibility issue.

This has been a DERP moment brought to you by Sebben!

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[Sebben]

Re: VLTOR MUR-1A and DD RIS II compatibility issue.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: redirt78</div><div class="ubbcode-body">Aluma-black. $10 from Brownells for a 3oz bottle. Heat the part up then apply liquid with a small paint brush or q-tip. A lot better than a sharpie.


I think you will like that combo, I have the same upper with a 14" DD Lite rail </div></div>

Thanks Red.

Hey on the bright side now people don't have to search on Google for hours for no answer! hope this thread helps someone else!

Oh and yes it is a PITA getting the screws in lol it's 30min of slowly screwing!

 

[grkmec]

Re: VLTOR MUR-1A and DD RIS II compatibility issue.

A few years back, I had Wes at MSTN build me an upper where I spec'd a MUR + DD RIS II. Here is a pic

So it does work!

 

[johnson]

Re: VLTOR MUR-1A and DD RIS II compatibility issue.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Sebben</div><div class="ubbcode-body">
LOL looks like im breaking out the sharpie! Or is there anything that can cover up that ding i put in the receiver? </div></div>
I don't know the name but welding supply places should have something similar to Aluminum Black. I think it's a bluish liquid.