VLTOR MUR & Upper Flex tests

[wacki]

Anyone got any more recent info on flex tests & the VLTOR MUR? I'd like to see some data on the MUR

Quote from flex tests:

I used a small torch to apply heat the barrel nut/chamber area of the upper receiver assembly. Lightly feathering only the chamber area with the torch, I took the temperature to 200 - 220 deg (F) -- not at all an unrealistic temperture for the rifle. The results here were very interesting, the dial gauges reacted immediately to the heat....<snip> ...This test (I believe) induced enough alignment error to believe that not only the reliability, but the structural integrity of the weapon may have been compromised.

20 lbs is a lot at the range, not much at all if you are jacked up on adrenaline and getting shot at.



Stickman #1

. If you are ever able to look at receiver flex testing, you will see the MUR really shines.

Stickman #2 on broken bolts

If you think back a year or two, there was a thread on bolts snapping under hard combat use. Torque on the rail (resulting in receiver flex) via the VFG while the end user was under high stress/ mass amounts of adrenaline.

Not something that is important for most people, but for the people that it matters to.....

Upper flex testing


https://www.m4carbine.net/showthread...sting-Part-One

https://www.m4carbine.net/showthread...sting-Part-Two

[ESK]

When that test was conducted, the MUR was made from 6061T6 billet (extruded barstock) and at that time, it was stiffer than the standard A4/M4 G.I. spec. upper receiver by 20%. MURs are now made from a forging of 7075T6 and are now twice as stiff as a standard A4/M4 upper receiver. If anything, the MUR is twice as strong/stiffer then the MUR that was used in the mentioned flex test.

[markm]

We have this ham hock 18" WOA barrel that I need to get a MUR for. The barrel probably weighs more than a complete KMR upper with BCG.

[Kill By Number]

Sad but it seems the link is broken to the Flex test #2 pages 3 and 4. I can't get anything to pull up with the results. Any ideas on how to find more of the original test info?

[Eurodriver]

At what point does one sacrifice weight for strength?

[markm]

At what point does one sacrifice weight for strength?

Depends on the build. The MUR isn't noticeably heavier than a standard upper. And any additional weight is behind the barrel nut. Adding weight out front of the center of gravity is more unpleasant then behind.

And if you're dangling a can out front, a strong upper is worth every penny and ounce.

[wacki]

And if you're dangling a can out front, a strong upper is worth every penny and ounce.

Maybe, but I need to see data. There are no shortage of engineers and experienced gunsmiths that feel the MUR is a waste of money.

[markm]

Maybe, but I need to see data. There are no shortage of engineers and experienced gunsmiths that feel the MUR is a waste of money.

What's your background out of curiosity? If you're an engineer, by all means... I doubt these "experienced gunsmiths" have the laser equipment to measure this type of thing.. so who gives a **** what cleatus and jethro think? The MUR very well could be a waste of money for someone deploying it in the wrong application.... or dumping it in the middle of a bunch of DPMS or LWRCi junk.

If I remember correctly, the MUR is the result of a request by the military to study bolt breakage. Now I'm not convinced that receiver flex is a significant bolt breakage cause... it might be, but I don't know for sure. I do know the people behind the MUR aren't going to make up stiffness claims that company X could easily refute.

[Iraqgunz]

I have no doubt that there are people who say this- they also are usually the same ones that say Carpenter 158 is unnecessary, DPMS and Bushmaster are just as good "MILSPEC", etc...

But, I will say that after I had a kaboom and I saw how little damage my upper suffered compared to others I think there is something to it. My 11.5" SBR upper was built with a MUR from the beginning and that bolt had over 12K rounds on it before any issues (due to the kaboom) before I changed it.

You also have ESK above who is VERY FAMILIAR with the MUR and knows a few things about designs and engineering.

Maybe, but I need to see data. There are no shortage of engineers and experienced gunsmiths that feel the MUR is a waste of money.

[wacki]

If I remember correctly, the MUR is the result of a request by the military to study bolt breakage. Now I'm not convinced that receiver flex is a significant bolt breakage cause... it might be, but I don't know for sure. I do know the people behind the MUR aren't going to make up stiffness claims that company X could easily refute.

Are they making any claims? I can't find any data whatsoever on the MUR. Any links to the mil request or testing? All I can find is a vague one sentence promise of stiffness from their marketing material. Not the most reassuring reason to spend an extra $100.

I've emailed VLTOR direct and I'm haven't gotten very far. Will prod them again.

As for background, I've got more than enough formal education to look at the data and think critically and plenty of friends with real world manufacturing experience to keep the ivory tower effect in check. So I'm highly interested in impartial data / experiments. Unfortunitally right now I have nothing.