Now for the build.
Upper receiver
I opted to go with a real steel VLTOR MUR this time as I have heard and personally experienced some problematic issues regarding brittle fractures at the barrel attachment point due to poor material choice and design.
From left to right we first have the 1st generation WE 416 where the walls at the barrel attachment points are 1/8 inches, the middle is a 2nd generation WE 416 where the wall are now reinforced with a thickness of 3/16, and a DYTAC MUR with thickness of 1/8 inches.
Make sure you find parts that are of the same version.
Now to solve this problem of fractures at the barrel attachment point I decided to go with a real steel VLTOR MUR upper, forged and milled from a billet of 7075 aluminum, it best not fail. As you can see I had to JB weld my previous 416 upper, it was fractured during production or shipment.
Now there are a couple of dimensional differences between the WE and RS upper, mainly being the internal diameter of the bore. The WE has 2 diameters, the larger being the same as RS starting from the top of the barrel attachment to the end of the threads, and then a smaller diameter throughout the upper, this is to hold the inner barrel/hop up assembly in place.
A number of WE M4 owners have the problem of the bolt not locking back most or all of the time, this issue can be commonly caused by:
- Insufficient surface contact of the bolt and bolt stop
- Angled contact between bolt and bolt stop
A solution to this would be to add AEG shims between the bolt stop and lower receiver. Instead of faced contacting like --> // <-- which shears off at an angle, they will contact like this -->||<--
In addition to this step if your bolt stop continues to fail, or if the face is worn, you can braze on a thin sheet of steel, about 0.75ish millimeters. It was shaped into an "L" and brazed at the end using a propane torch and silver solder. It has been locking 100% after 10+ mags. The extra bit of material helps as more surface area of the lock contacts the bolt.
This method is not permanent and may be replaced or removed in the future
Another method would be to tack a bead of weld, then file it down.
Another modification is needed in order for the MUR upper to fit due to clearance issues. Internally, the RS upper is not wide enough to accept the "mech box", which protrudes 1 or 2 millimeters from the top of the lower receiver.
From left to right we have, WE, RS VLTOR, and DYTAC. Notice the upper receivers all have different relief cuts in the walls.
The VLTOR upper has thicker walls and no relief cuts so for the lower receiver to clear this, either the walls have to be machined thinner or the "mechbox" has to be made thinner. I chose the latter.
Lastly, the barrel attachment point has the most noticeable difference as 3 cuts can be seen on the WE and only one on the RS. On the WE, the cuts keep the inner and out barrel from freely turning.
Since the WE barrels have 2 protruding notches on opposite sides, it is necessary to remove them in order to fit on top a RS upper.
First, a step must be taken before the removal of the notches. Since the RS upper does not have that smaller inner diameter ridge to keep the inner barrel assembly from sliding back into the upper, an alternative method must be utilized to keep this from happening.
What I still need to do is to drill and insert a roll pin at the 12 O’clock position into the barrel spacer, this acts as the locator pin and keeps the barrel in place.
Another way to keep the outer barrel in place is take the barrel spacer and outer barrel, affix them to each other, put them in a vice and crush the notches into barrel spacer. This is a more permanent way of affixing the barrel to the spacer, however there are many other methods, I chose this because I don’t plan on un-assembling them.
Here is the bolt with the pin which allows the bolt to be pulled back by the charging handle.
I did not wish to mod the RS charging handle so I opted to mod the bolt instead.
She's finally done. I think.
- BCM Gunfighter Mod 3
- Battle Arms Development BADASS
- DSA Stock Tube Mil-spec
- Magpul ASAP
- Magpul CTR [Mil-spec]
- Magpul MIAD Grip
- Magpul EMAG
- Magpul PMAG
- Magpul RSA
- Magpul XTM Rail Covers
- PMC 7" Barrel
- TSC Anti-rotation Links
- TSC Gear Sector Hand-Stop
- Troy Ind. Battle Rail Covers
- Troy Ind. Modular Combat Grip
- VLTOR MUR Upper receiver
- WE Stock Lower
- WE HK 416 Sights
- Unknown Make 7.5" DD RIS II
