By way of background, here in California semi-automatic shotguns like the M4 must have fixed stocks and 18" barrels. Working within these constraints my goal was to create a minimalist design optimized for my dwarf like body and squared of stance in a home defense / CQB role. Previous experimentation with an OEM collapsible stock helped me discover the appropriate LOP and Drop for my physical build and purpose. Range time and training will be needed to see if i got it right.
Anyhow, the details.
1. Debrazed the front iron sight and smoothed re-coated the barrel.
2. Removed the OEM rear sight and picatinny rail.
3. I did a ton of research and talked with several companies to try to get a full length rail made for the M4, all to no avail. So I built it myself using a Night force gunsmith rail blank. The NF profile I used allowed the full width contact radius with the receiver I was looking for. I milled the bottom mating radius on the rail section with a 1.5" ball end mill and then hand lapped the rail to the receiver. I then cut to length and shaped the rear rail section and de-horned to eliminate all sharp corners. I carfully indexed the receiver to map out the hole locations using a center finder and the digital readout on the mill. I then then drilled and counter bored the new rail to utilize the 5 OEM picatinny rail screws and drilled and taped for the two OEM rear sight screws. For those that have had occasion to remove a rear sight you will have noticed there is a third hole in the receiver between the two countersunk holes used to mount the rear sight. I purchased an additional rear sight screw and lock washer from Midwest Industries for this third hole. To furthur complicate the task it turns out that Benelli uses some kind of odd metric countersink for all these screws so I had to have them custom ground. Fortuantely, I have a great source here in Oakland. If anyone needs these cutters I would be happy to loan them out.
4, Installed the ATI pistol grip.
5, Fabricated a short LOP fixed stock by welding together the ATI buffer tube, butt plate and end cap. I actually had to mill the butt plate to allow the buffer tube to pass through the plate before welding. I then used JB weld to fill the bottom channel and holes in the buffer tube (used for telescoping) and fill the recesses in the butt plate. I then fillited and faired the surfaces. In hindsight I should have just fabricated my own butt plate as this would have saved a bunch of filling and fairing. It is worth noting that the ATI parts are absolutely top quality.
5. Sniper gray Cerakote by LEO Arms in Concord.
6. I am still torn about the odd color of my first generation A&S trigger guard. I like the durability and function of the anodizing and so did not want to Cerakote this part. I am going to shoot the thing for a while before deciding what I might do about the poor color match.
7. The big benefit of the custom full length rail is the flexibility with regard to optics. Shown is a Shield SIS sight with a UTG Bull Dot Green laser just behind. The laser projects a huge dot through the mount of the Shield sight that is bright enough illuminate and identify a target in a fully dark room. Looking through the Shield sight you see both the circle of red dots of the Shield sight and the huge green dot of the laser. Testing will determine if the UTG laser holds up to the M4 recoil abuse.
Thanks for looking,